In this paper, we experimentally study the performance of a large effective area non-zero dispersion shifted fiber over distances characteristic of metropolitan and provincial area networks, with a wide variety of commonly used transmitter types. The experiments are performed without dispersion compensation to simulate current network designs. The transmitters tested include externally modulated lasers, directly modulated lasers, lasers with integrated electroabsorption modulators, bit rates of 10 Gb/s and 2.5 Gb/s, and wavelengths from 1310 nm to 1610 nm. We find that the non-zero dispersion shifted fiber compares favorably with standard single mode fiber for many transmitters, offering reach advantages of 3-4 times in the 1550 nm band. Deployment of such a low dispersion fiber in metro/provincial networks may allow the use of some transmitters currently not practical, such as 10 Gb/s directly modulated lasers in the S-, C-, and L-bands. In general, it provides comparable or superior performance with today’s current transmitters, and allows the possibility for future upgrades to higher bit rates and longer link lengths that may not be feasible with standard single mode fiber.

We study the modal birefringence behaviour of a near-elliptic core index-guiding photonic crystal fiber (PCF) intended for high birefringence applications. The analysis is based on a semi-vectorial field convergence algorithm combined with the perturbation correction technique of mode calculation. The approach is accurate, simple to implement, and much faster than any of the existing methods. The efficacy of our design analysis has been verified by comparing the results with otherwise known solutions. Using this analysis as a design recipe, we have realized PCF of reasonably high birefringence characteristics.

Low-loss and symmetrical mode-field optical waveguides were directly written in a pure silica glass by nearinfrared femtosecond laser processing. By optimizing laser processing parameters, such as the pulse duration and the pulse energy of femtosecond laser pulses, we demonstrated the propagation-loss reduction and the mode- field diameter (MFD) aspect ratio improvement. We have achieved the propagation-loss of 0.10 dB/cm and the MFD aspect ratio of 1.0 at the wavelength of 1550 nm at the same time.

An optical phase conjugator is used to enhance the robustness of optical pulses to polarization dispersion. The polarization components of optical pulses form a breather in birefringent fibers firstly and make a polarization component along fast axis compressed through spectra inversion function of the optical phase conjugator. The two polarization modes are compressed further due to the cross-phase modulation effect and trap each other fully in time domain. The optical phase conjugator is required to settle down before higher birefringent fibers in order to suppress the influence of birefringence effectively. The limit value of δ reaches 7.5 that can be suppressed by enhanced robustness of the optical pulses by using the optical phase conjugator in the case that each polarization component is a fundamental soliton. Moreover, the function of the optical phase conjugator will reduce the delay of optical pulses for a different polarization angle.

In this paper, a 850nm-optimized dispersion-unshifted single-mode optical fiber was introduced. This type of fiber is completely compatible with G652 series fibers, but its bandwidth at 850nm wavelength has been optimized in order to fitting the potential applications. This fiber was manufactured by PCVD (Plasma-active Chemical Vapor Deposition) method. In order to increasing the 850nm bandwidth, the core-RI-profile (Refractive Index) of this fiber was designed as graded-index profile. With a piece of about 36km length fiber, some relevant geometric and optical characteristics had been got. The core diameter, MFD (Mode Field Diameter) was about 13 micron and 9.6 micron respectively. The cut-off wavelength and zero-dispersion wavelength was at 1315nm and 1323nm nearly. The attenuation at 1310nm and 1550nm was less than 0.34dB/km and 0.19dB/km respectively. With all of these results, this 850nm-optimized fiber was completely corresponding with specifications of G652 series of fibers. Meanwhile, OFLB (Over-Filled Launch Bandwidth) test showed the bandwidth at 850nm was larger than 400MHz.km comparing to about 150MHz.km OFL bandwidth of normal G652 fiber. Because of the pretty large 850nm bandwidth, this fiber could be possibly used at 850nm wavelength in LAN (Local Area Network) or DSN (Data-Storage Network) field. In order to validating the compatibility with G652 fibers, the splice loss between this fiber and normal G652 fiber also had been tested.

In this paper, we report a MEMS-variable attenuator (VOA) with unique SOI based electrostatic torsion mirror structure to realize simple fabrication process and low voltage, stable operation, as well as high production yield. In the proposed device, attenuation principle is a simple beam deflection method by using tilt mirror, which deflects the incoming optical beam, and thus changes coupling loss at the output fiber end with respect to the beam mode profile. The whole MEMS structure is made of silicon-on-insulator (SOI) wafer, where a shaped through-hole made by deep RIE (DRIE) under the half side of the rotational mirror suspended by torsion bars automatically defines the electrode on the opposite side with respect to the upper device silicon layer. A number of careful design tips are taken into account for high temperature stability and anti-shock/vibration performance. Fabrication process of the chip is also as simple as it is designed so that it only requires two DRIE processes and three photolithography steps. For the finished pigtail module, dual fiber with an aspherical collimator lens, and a CAN package with MEMS chip mounted inside are tightly welded by YAG laser in order to ensures both environmental reliability and operational stability. Driving voltage as low as 5V provides attenuation range over 45dB while maintaining anti-shock/vibration characteristics. Selective deposition of metal layer coating on the circular mirror section suppresses temperature dependent fluctuation less than 0.5dB at 20dB attenuation over 0 to 70degC range by decoupling bimorph effect of metal layer from the electrostatic operation.

The mission-critical nature of high-speed networks imposes stringent requirements for high availability. Resilience is achieved through highly reliable network nodes, and through network protection / restoration mechanisms that rely on various forms of redundancy and fault tolerance. Although data networks can be restored at the IP layer, carriers and enterprises alike, are increasingly relying on protection at the physical layer, to achieve fast and reliable recovery. Faulty network components (nodes or links) are quickly identified and restoration takes place by automatically bypassing them or replacing them with spares. Switchover from a failed component to a spare is called "Protection Switching’. 1:N protection switching, in which a single spare is used to protect several (N) components, was found to be most cost-effective. Furthermore, operational expenses of fiber-based (optical) networks can be minimized through the use of all-optical switches that are transparent to data rates and protocols, allowing easy network upgrades. This article discusses issues associated with optical equipment protection switching and describes a new breed of intelligent protection systems, based on Planar Lightwave Circuit (PLC) technology.

We proposed a compact design of cascade Y-branch splitter devices. The new device consists of a 1×N branching region and a fan-out region. The length requirement of this new design is analyzed, the results show that the device length can be sharply cut, when N is larger than 8. As an example of this new structure, we designed an 1×16 branching splitter by K⁺/Na⁺ ion-exchange in BK7 glass, the smallest S-bend radius is 30mm, and the total bends length is about 20mm, it is 69% length of ordinary splitter.

Dense optical bus arrays and optical routing components have limitations due to crosstalk between the waveguides and interference causing from system parameters. In this paper, crosstalk and interference penalty behavior in single mode polymeric optical bus arrays and optical multiplexers are investigated. It is shown that crosstalk power penalty and hence the waveguide density in these devices is controlled by crosstalk occurring due to the neighboring waveguides as well as systems parameters such as optical source linewidth, frequency spacing between sources, optical source and photodetector noises, waveguide parameters and others.

We propose using a novel multifunction optical filter with cascaded sagnac circuits for future smart wavelength division multiplexed network system applications. The coupling coefficients of the couplers in cascaded sagnac circuits are apodized according to the Gaussian function. By properly adjusting only two parameters, the coupling coefficients are convex-apodized or concave-apodized. For the former, we can obtain passband filter and improve response functions such as flatness and steepness; for the latter, it is possible to gain comb-like transmitted responses.

We investigated the issue of dynamic gain control for multi-wavelength pumped broadband distributed Raman amplifiers. For the first time, we proposed that using a pair of fiber gratings in a section of the transmission fiber, a gain clamped broadband distributed fiber Raman amplifiers can easily be made through all optical method. The method is based on the utilization of the pumps’ interactions and uneven gain property along the fiber in the amplifier.

We present the first results of a new approach for creating graded-index polymer optical fibres (GIPOF) with integrated switchable Bragg gratings. The polymer multi-mode fibre used is made of polymethyl methacrylate (PMMA) by the interfacial-gel polymerisation technique and has got a parabolic refractive index structure. Former attempts to write Bragg gratings in this type of GIPOF fibres were not successful without squeezing the fibre by which the optical performance is reduced. This problem can be overcome by adding a photochromic dopant in the fibre core. By bleaching the dopant, reflection gratings can be created with the interference pattern of two interfering laser beams with a wavelength around 500 nm, which does not affect the rest of the fibre, but only the photochromic molecule. Before writing, the dopant is initialised with a simple UV-broadband source. Because of the photochromic effect, the grating can be removed and written again in a totally reversible way. It is clear that these systems can have a lot of applications and possibilities. The characteristics of these gratings are measured experimentally in fibres and in thin polymer slices and results and applications are discussed.

We demonstrate the simple relationship between the refractive index modulation, the chirp coefficient and the reflectivity of the large chirped Bragg grating. When applying it to design the gain flattened filter, we can get almost the same profile as the custom requests. At last, we propose the procedure using this method to write the gratings.

Current optical communication systems are more and more relying on the advanced opto-electronic components. A series of revolutionary optical and optoelectronics components technology accounts for the fast progress and field deployment of high-capacity telecommunication and data-transmission systems. Since 1990s, the optical communication industry in China entered a high-speed development period and its wide deployment had already established the solid base for China information infrastructure. In this presentation, the main progress of optoelectronics components and technology in China are reviewed, which includes semiconductor laser diode/photo receiver, fiber optical amplifier, DWDM multiplexer/de-multiplexer, dispersion compensation components and all optical network node components, such as optical switch, OADM, tunable optical filters and variable optical attenuators, etc. Integration discrete components into monolithic/hybrid platform component is an inevitable choice for the consideration of performance, mass production and cost reduction. The current status and the future trends of OEIC and PIC components technology in China will also be discuss mainly on the monolithic integration DFB LD + EA modulator, and planar light-wave circuit (PLC) technology, etc.

As the size of diffracting structures with a diffractive optical elements is on the order of or less than the illumination wavelength, it is necessary to use a rigorous electromagnetic theory of diffraction to accurately analyze its performance. A rigorous electromagnetic analyse of two-dimensional diffractive microlenses is presented. Without paraxial approximation, the focusing performance of diffractive microlenses with different f-number have been determined including diffractive efficiency with different incidence polarizations (TE polarization and TM polarization), and different profile structures (continuous profile, 8-level profile and 2-level profile) of mircolenses, respectively. Both scalar and rigorous analyses are performed on all these diffractive microlenses.

Y-branch is an important optical passive component. It can be used as power splitter and mode conversion. In this paper, a variable optical attenuator was designed using an asymmetric Y-branch. The device was simulated by FDBPM (Finite Difference Beam Propagation Method). It has the characteristics of compact size, large scale dynamic attenuation and low power consumption.

A novel 16-channel 50-GHz spacing interleaver for dense wavelength-division multiplexing (DWDM) systems has been realized using Ti:LiNbO₃ waveguides with the corrugated Si overlays. High refractive-index Si layer on LiNbO₃ waveguide enables a large index perturbation to strongly affect the mode index of the composite structure. The reflection spectra strength of each peaks and bandwidths of the individual channels are increased by interleaving several sampled gratings together. The modal characteristics have been analyzed by employing vectoric finite element method. The reflectivity has been obtained by formulating the transmission matrix of the structure. An odd-even channel separator with a gratings length of approximately 11 mm has been fabricated and its reflection spectrum has been measured. The -1-dB channel bandwidth is ≥ 0.2 nm and the sidelobes are < -20 dB.

The paper describes the design features and characteristics of an embedded fiber Bragg grating (FBG) pressure sensor that has been developed to measure forces applied in the direction perpendicular to the fiber axis. This FBG-based pressure sensor provides an absolute measurement in terms of wavelength shift, which avoids problems of signal intensity fluctuation often encountered by conventional intensity-modulated or phase-modulated pressure sensors. The initial outcome of our study indicates that direct sensing using bare-FBG is infeasible for real applications due to its non-linearity and limited range of force sensing. However, when the FBG is embedded into some composite material, the sensor exhibits excellent linearity, high stability and reliability over a wider force-sensing range, making it a potentially viable sensing element. When an FBG is embedded into some fiber-reinforced composites, a level of sensing force of up to 60N with a sensitivity of 3.96 pm/N and resolution of 1pm (equivalent to 0.8με) is achievable without causing permanent deformation to the FBG.

A novel apodization technique is presented using a combination of a phase mask with an amplitude mask of variable mark-space ratio for fabricating sampled Bragg grating (SBG) for the first time. This technique only needs single exposure process instead of double exposure to complete apodization and apodization compensation in SBG fabrication. From our numerical simulation and experimental results, it can be seen that this technique is promising in changing reflection spectrum and reducing the ripple of group velocity delay of the sampled fiber Bragg gratings.

Now a new technology has emerged called “Fiber Bragg Gratings” which allows very narrow band width filters to be made in optical fibers. These fiber gratings have been applied to the communications industry at the 1.55 micron telecommunications wavelength, but there is evidence that the same technology will work at the 589 nm wavelength of interest to Na Fluorescence Lidar. Because of its high reflectivity (99%) and narrow band width (0.1nm), it can be used instead of present dielectric interference filters and Fabry-Perot etalon in the Lidar receiver, which will drastically improve the optical efficiency and the signal-to-noise ratio of Lidar. It will also drastically simplify the Lidar receiver.

Delay ripples of chirped fiber Bragg gratings (CFBGs), which a CFBG can compensate 200 km long optic fiber's dispersion, have been analyzed in detail. A numerical simulation of cascaded grating delay ripples has been done by Schroedinger equation and compared with experiment of 1,000 km transmission over G652 fiber by 5 groups of CFBGs dispersion compensation. The research shows that the system degradation depends on the delay ripple period, which is 0.01~0.1nm through a lot of experiments, and amplitude of delay ripple. We had experimentally studied fluctate of power penalty depend on ripple perod of CFBGs when source wavelength changed +/-20GHz around CFBGs center wavelength, the results of theory agree well with these of experiment.

We discuss recent surge of interests in coarse DWM (CWDM) applications and implied challenges for low cost and compact devices. We show that for further cost-reduction and performance enhancements, an old WDM packaging architecture can be revitalized to address the new compact CWDM (CCWDM) filter challenges. In particular, we demonstrate a CCWDM filter platform and show its use in both an 8-channel Mux/DeMux and a 4-channel OADM applications.

The technical process of spin coating polymer thin film used in thermo-optical switches fabrication was thoroughly described. High performance polymer films were prepared, whose refractive index, thickness and loss were tested. The effects of each technical parameter, as spin coating rate, solution concentration, spin coating time etc., on the optical and mechanical properties of the polymer thin film wave-guide were analyzed. An experiential equation was also given by least square fit method. The prepared films had comparatively low loss, desired thickness, and were of perfect quality. Some other thin film qualities as absorption spectrum and surface profile were also given to show the characteristics of the films.

A novel supercell overlapping method is developed to analyze the PCFs. The dielectric constant of the PCF is considered as the sum of two different periodic dielectric structures which can be expanded in cosine functions.

Combining perfectly matched layer (PML) for the boundary treatment, we present an efficient compact 2-dimensional finite-difference time-domain (2D FDTD) method for modeling photonic crystal fibers. For photonic crystal fibers, if we assume that the propagation constant along the propagation direction is fixed, three-dimensional hybrid guided modes can be calculated by using only a two-dimension mesh. Because of using the real variable method, the computation time, i.e., it is of order N. Comparing with the plane wave expansion method, FDTD make the computation time and computer memory are significantly reduced. The numerical results for a triangular lattice photonic crystal fiber are in very good agreement with the results from the local basis function method. This method can easily be used for any complicated inclusions.

The key for optical fiber manufacturers to remaining profitable in today’s environment is cost reduction, requiring a hard look at raw material and processing costs to evaluate areas for savings and materials reduction. In this paper we examine the use of computational fluid dynamics (CFD) as a tool to study fiber-manufacturing processes. Specific examples are given of the use of CFD to analyze the consumption of helium as a coolant gas in fiber drawing, with the objective of showing that helium usage can be reduced by either optimizing the operation of existing cooling tubes or through improved cooling tube designs. With respect to the drawing of optical fiber, the cooling tubes should be ideally operated at their most efficient conditions such that the cooling capacity requirement is satisfied with minimum usage of cooling gas (e.g., helium). Optimization of the fiber cooling process can be realized by evaluating the cooling efficiencies of different designs of cooling tubes, and under different operating conditions. The use of CFD simulation can avoid mistakes and reduce the cost and time of process development.

In this paper, based on the Rayleigh Quotient Iteration method, a new treatment is developed to solve the complex eigenvalue problems, which arise from the analysis of the optical wave propagation in Slab waveguides with some perfectly matched layers. Numerical examples illustrate that this treatment is more efficient and feasible. It can be widely applied to the numerical calculation of optical wave propagation in open waveguides.

Dispersion-compensating chirped fiber gratings provide a compact low-loss means of compensating fiber dispersion. They are potential candidates for per-channel tunable dispersion compensation devices [2]. Group delay ripple (GDR) is the principle reason restraining the practical implementation of chirped fiber Bragg gratings and many papers indicate how the GDR impairs the systems performance [1, 3, 4]. S.Jamal has indicated that the period of the group delay ripple has much important influence on the systems performance [1]. But the ripple period of the chirped fiber grating was not consistent along side the grating, and Michael Sumetsky has explained the cutoff phenomenon of the high frequency in [2]. Because the period of the chirped fiber grating changed with the wavelength and the components of different frequency overlapped with each other, the time-frequency analysis was needed to descript the time-frequency distribution of the GDR of the grating. [5]

The Integrated acousto-optic tunable filter have the potential to perform the OADM or OXC functions, which play significant role in WDM optical network. The characteristic of the acousto-optic mode conversion is sinc²-like functions with high sidelobe intrinsic. The high sidelobe level lead to serious crosstalk in the WDM optical network. The theory of weighted coupling for IAOTF has been presented. And the filter response using four suggested weighted functions has been calculated with the matrix methods. Significant suppression of sidelobe level has been achieved by employing the techniques of weighted coupling. It is a valid approach to reduce the sidelobe of IAOTF by choosing propriety weighted function and a realized way.

Based on self-imaging effect of multimode interference couplers, general self-imaging and overlapping-imaging properties are analyzed. The positions and phases of the self-images are directly related to the position of the input field and positional number. Simple expressions for positions are also derived. And the guided-mode propagation analysis is used to confirm the analytical results.

Long period fiber gratings couple the fundamental guided mode to forward propagating cladding modes. A Characteristic of LPGs in SMF is that their spectral properties (resonant wavelength and coupling strength) are sensitive to the refractive index of the surface surrounding the cladding region. Because of this, LPGs are typically packaged unrecoated to obtain insensitive spectral properties. In this paper the effective index model combined with the coupling-mode theory are used to study the characteristics of LPGs based on photonic crystal fiber (PCF). After plenty of numerical simulation, the results demonstrate that PCF-based LPGs will be more insensitive to the surrounding medium than those written in SMF.

Optical low pass filter (OLPF) made of artificial crystal is demonstrated. From the view of 1-D, 2-D, 3-D crystal’s filter and gratings filter, the design of relative parameters and the influence of processing are discussed..

Polarization mode dispersion (PMD) in chirped fiber Bragg grating (CFBG) is experimentally studied in detail. The effects on PMD characteristics of fiber birefringence, group velocity dispersion and group delay ripples in CFBG are investigated experimentally. Simultaneously, the impairments on 10Gb/s optical fiber transmission system due to PMD in CFBG are also demonstrated experimentally.

Polarization mode dispersion (PMD) is a serious limiting factor for high bit rate optical communication systems. It is important and necessary for PMD researchers to know the joint statistical characters of the second order PMD (SOPMD) vs. differential group delay (DGD) and how about the penalty contributions of PMD vector’s components. In this letter, we first get the joint statistical distributing range and joint probability distributing density of normalized DGD slope, depolarization, and the SOPMD vs. normalized DGD, and the average values of normalized DGD slope and depolarization vs. normalized DGD. The results are independent with PMD value, and the depolarization is the main contributor for SOPMD value. We secondly analyze the system penalties induced by PMD vector’s components. The DGD is the main contributor for the maximum system penalty. When the sate of input polarization (SOIP) is principle state of polarization (PSP) input and fixing DGD value, the SOPMD is the main contributor for penalty varieties, the main penalty contributors are DGD and depolarization. Ignoring DGD slope effect, with PSP input and fixing DGD value, the system penalty first keeps constant (near zero dB) and then increases linearly with depolarization value increasing; with PSP input and fixing depolarization value, the system penalty decreases with DGD value increasing and the curve has slightly fluctuant.

The theoretical model of DOP degraded by PMD is presented, with which one can analyze and maximize DOP directly from two factors, the magnitude and the direction of the PMD vector. According to this, one method to counteract PMD of the link is adjusting the compensating vector’s magnitude to achieve a zero-magnitude total PMD vector in the system, another is changing the vector’s direction adaptively to make the input signal align with the total PMD vector. Further, the NRZ signal DOP property degraded by PMD and the system’s BER against the change of PMD are obtained in the first experiment, also, the PMD compensation performance-degradation as the scrambling rate is increased is studied in the second experiment, in which it is concluded that the scrambling rate of polarization state has an important impact on a reliable, repeatable PMD compensation in a reasonably short time.

We used a two-stages three degrees high-order polarization mode dispersion (PMD) compensating structure. The former stage adopts polarization controller and fixed time-delayed line that is consisted of polarization-maintaining fiber. The second stage adopts a nonlinear chirped fiber grating that is made by hydrogen-doped G652 fiber, which is used to adjust the magnitude of PMD. Use this kind of fiber grating of which the time delay can be adjusted to form the second stage, and then realize the first-order and high-order of PMD compensating on a 40Gb/s OTDM system. The compensator can be used as chromatic dispersion and PMD compensation. The result of experiments revealed that signal’s eye digraph and pulse shape are recovered distinctly.

P-OTDR is the effective method for measuring distribution of PMD in a single-mode fiber, this paper analysis the effect of coherence of light source on measurement, that, when the width of input pulse is short enough, this effect can be neglected. But, when we estimate the effect of width of pulse on the measurement results, the coherence of light source must be considered.

We propose a single-chip-based module that provides the entire switching/monitoring/equalizing/shuffling functionality needed in 8-channel fully reconfigurable optical add/drop multiplexers. This subsystem on a chip includes an array of switches for adding/dropping individual channels, optical power taps and integrated photodetectors for power monitoring, variable optical attenuators for channel power equalization, and optical cross-connects for channel shuffling at the add and drop ports for full wavelength agility. The chip is based on a polymer-on-silicon platform that allows hybrid integration of passive and active elements. Waveguiding circuitry is built in an optical polymer, and it includes thermo-optic switches, variable optical attenuators, and power taps. Out-of-plane coupling mirrors are formed by ablation of 45° slopes in the polymer waveguides with an Excimer laser, followed by metalization. A self-aligning flipchip process is used to mount photodetector arrays on top of mirrors fabricated in tap waveguides for power monitoring. The worst-case fiber-to-fiber insertion loss for the proposed module, between 1528 and 1610 nm wavelength, is 1.2 dB from Input to Output (Express), including 4% tapped power, and 1.2 dB from Input to Drop and from Add to Output (4.1 dB with 8×8 shuffle cross-connects). The polarization dependent loss for any path is under 0.2 dB, and the polarization mode dispersion is under 0.05 ps. The channel-to-channel crosstalk is 50 dB, the switch extinction is 45 dB, and the return loss is 50 dB.

Some research results on tunable fiber gratings and their applications are presented in this paper. Dynamic characteristics of thermal tuned FBG by surface coated heater are described. Tuning characteristics and effects of friction in compression tuning packaging are analyzed. Tuning behaviors of LPG in Panda fiber are described and discussed. A pressure sensor by LPG is presented. And demodulation for sensor systems by using tunable FBG is proposed.

Planar lightwave circuits based on silicon are playing important roles in integrated optical systems. The integrated waveguide turning mirror (IWTM) is essential component for the compactness of optical devices. We designed and fabricated an integrated waveguide turning mirror with a 90° directional change in SOI. The mirror was etched by induct-coupled-plasma etching (ICP) first. Then the surface was enhanced by wet anisotropic etching. This two-step process introduced a compact IWTM with smooth and vertical surface. Compared with the mirror fabricated by wet anisotropic etching only, the mirror fabricate by the two-step process is better to meet the requirement of compact design.

By modeling a long optical fiber as 1000 small fiber segments, we simulate the statistical characteristics of PMD up to second order including the DGD, the parallel component of DGD slope, the perpendicular component of depolarization, and second-order PMD (SOPMD) denoted as the sum of the both components for 106 fiber realizations. Through simulations, we found that the higher PMD value, the larger the covered range of the DGD slope, PSP rotation rate, depolarization, and SOPMD is. For certain PMD value, although the maximum (average) PSP rotation rate decreases rapidly with instantaneous DGD value increasing, the maximum depolarization increases with instantaneous DGD before DGD reaches 2 times of PMD value, then begins to decrease. The average depolarization increases almost linearly with instantaneous DGD value. Maximum DGD slope also increases firstly, then decreases with instantaneous DGD, but average DGD slope almost does not change with DGD value. Also, we found by simulations that depolarization dominates in second-order PMD and DGD slope only has little contribution.

Twin core erbium-doped fiber is fabricated using a combination of MCVD, solution doping and post processing technique. This paper mainly study the birefringence of twin-core Erbium doped fiber including geometrical and stress birefringence. First we analysis the mode distribution of twin core fiber and geometrical birefringence by supercell lattice orthogonal function method using the structure parameters measured. Then the geometrical birefringence also calculated from the couple theory. The calculated result showed that two elliptical cores would have higher geometrical birefringence than two circular cores. Generally the Er-doped fiber is high Germanium doped to keep high Numerical Aperture (NA), which cause high thermal expansion coefficient difference between the core and the cladding, and the stress birefringence is anisotropic. According the distribution of stress field, we calculated the stress birefringence in the area of assembling of light power, which approximate to 10^-4. The investigation proved that twin core Erbium doped fiber has high birefringence and good polarization maintaining characteristics.

We have demonstrated an effective method for suppression of coupling from a guided mode to cladding modes in a fiber grating. The UV light pulse energy, repeated frequency and exposure time are controlled and optimized during writing process of Bragg grating. We can write advanced Bragg grating using optimum UV light parameters.

Optical add/drop filters using two-dimensional photonic crystals (PC’s) are presented for different designs. In-plane channel add/drop filter composed of two waveguides and an optical resonator system is very compact, but sensitive to the losses. While add/drop filter based on a contra-directional PC waveguide coupler is much more robust to the losses, and reasonable compactness is possible with careful designs. The possibility to utilize the PC dispersion properties to design optical filters is also discussed briefly.

The sensitivity of SONET p-i-n photodiode receivers with transimpedance amplifier (PIN-TIA) from OC-3 to OC-48 data rates measured by using a standard bit-error-rate tester (BERT) and a novel synchronous-modulation inter-mixing (SMIM) technique are compared. A threshold inter-mixed voltage of below 15.8 mV obtained by SMIM method corresponding to the sensitivity of PIN-TIA receiver beyond -32 dBm determined by BERT for the SONET OC-48 PIN-TIA receivers with a required BER of better than 10^-10 is reported. the analysis interprets that the inter-mixed voltage for improving the PIN-TIA receiver sensitivity from -31 dBm to -33 dBm has to be increased from 12.5 mV to 20.4 mV. As compared to the BERT, the SMIM is a relatively simplified and low-cost technique for on-line mass-production diagnostics for measureing the sensitivity and evaluationg the BER performances of PIN-TIA receivers.

Maleic anhydride-terminated polyimides(PMI) and copolyimides(PI) ,which are appropriate to fabricate PLC waveguides because of their very high thermal stability, excellent manufacturing performance, regulative refractive index, were prepared from 2,2’-bis-(3,4-dicarboxyphenyl)-hexafluoroproane dianhydride(6FDA), pyromellitic dianhydride(PMDA), maleic anhydride(MA), and 4,4’-oxydianiline(ODA) through two steps. The behaviors of crosslinked ractions occurred at the terminating maleic anhydride unites, thermal stability and optical properties (refractive index and optical losses) influenced by cured temperature were demonstrated through thermal analyses(thermogravimetric analyses(TGA) and differential scanning calorimetry(DSC)), IR Spectra and measurements of refractive index and optical losses. The results indicate that the exothermal crosslink reactions begin above 260°C and almost terminate after curing at 310°C for PMI, and its 5wt%-loss temperature is up to 447°C, which is closed to the PI’s(499°C). The refractive index decreases relatively significantly(4.1%) and optical losses increase from 1.86 to 2.62 dB/cm while the cured temperature increasing from 250°C up to 350°C.

A new method is presented in this paper to fabricate Fabry-Perot (FP) cavity with MEMS bulk wet-etching technology, through which FP cavities can be achieved with the cavity length from several microns to tens of microns. The parallelism of mirror elements can be well achieved without electrostatic control. Some FP cavities were achieved that the insertion loss was less than -8dB, the full width half maximum (FWHM) was about 2 nm, and the efficient finesse is up to 50. Some factors which influence the finesse have also been analyzed. The further work is ongoing.

In this paper, we present the design of a new type of high speed electro-optic (EO) modulator based on long period fiber grating (LPG). The outer layer of the LPG is fabricated by material with high EO coefficient, and a special material with ultra-negative temperature coefficient is used for the temperature compensation. This modulator can work steadily with low power microwave driver, its speed is very high and its cost is low. To our knowledge, this is the first time for a modulator designed with such a simple and effective structure.

Properties of the photonic bandgaps effect and guided modes in triangular photonic crystal fibers have been studied by means of a full-vectorial plane-wave expansion method. Photonic crystal fibers under consideration consist of a triangular array of microscopic holes forming a two-dimensional photonic crystal cladding and a defect as their core. The photonic band-structure for photonic crystal cladding structures and the field intensity distribution of defect mode with various air-filling fractions and defect size are calculated. Guidance mechanisms in photonic crystal fibers with different configuration are also investigated.

This article describes the design, development and characterization of a fiber optic sensor based on evanescent wave absorption in Long Period Grating (LPG) on multimode optical fibers, for the detection of toxic ammonia gas. The sensing length of the sensing element is only 10mm, but the dynamic range is as good as that of the conventional evanescent wave sensors. Sol-gel technology is employed for immobilizing a reversible ammonia sensitive dye on the grating region of a multimode fiber. Ammonia gas permeating into the immobilized dye, the color of the dye changes reversibly from yellow to blue with increasing concentration of ammonia gas. The concentration of ammonia gas can be determined by measuring the absorption at a given wavelength. The dynamic range of the sensor is from 0.027 to 2.04 mM/Ltr.

By developing an exact theory from the device structure based on the actual cylindrical nature of the transducer, an electrical model of the optical-fiber acousto-optic fiber phase-modulator (OFPM) coated with piezoelectric ZnO has been presented. Then, full details for the acoustic transducer resonator have been investigated, which are vital considerations in transducer design. Finally, to evaluate the validity of the model and the parameters deduced from that model, we use the practical coefficients and parameters in theoretical calculations. An excellent agreement exists between the model simulation results and experimental measurements.

A full vector method based on supercell lattice method is applied for modeling the microstructured optical fibers (MOF). With this new method, the class and degeneracy of modes in MOF are discussed based on symmetry analysis. We classify the modes of MOF into nondegenerate or degenerate pairs according to the minimum waveguide sectors and its appropriate boundary conditions. It is shown that the modes of MOF can be labeled by its step index fiber analogs, except the modes with the same symmetry as MOF. The doublet of the degenerate pairs in which both have the same symmetry as MOF will be split into two nondegenerate modes by the reduced symmetry of the fiber.

In variation calculus, the Fermat’ s theory is similar to the Hamilton’ s theory except that Hamilton’ s theory uses time as the independent variable to achieve minimum of a function while Fermat’ s theory uses space as the independent variable1. That is one of the essential differences between dynamics and optics. When time coordinate t in dynamics is substituted by space coordinate z, and generalized momentum is introduced, optics is obviously similar to dynamics. Thus, we can use corresponding quantum mechanics methods to handle similar phenomena in optics. First, in this paper, the concept of potential energy of Hamilton operator is introduced. Based on this, the law of energy minimization of a system, which is composed of two parallel waveguide, is used to deal with the transverse coupling between them. A more understandable result is gotten and the comparison between the results of classical electromagnetic methods is discussed.

Three new design waveguides for adiabatic directional full couplers are studied. We theoretically and numerically show that the performance of new full couplers is improved. Whe the length of the coupler is 4mm (the minimum local beat length is 2mm) at 1.57μm wavelength, the crosstalk is smaller than -35dB. For the length of the coupler is 4mm, the crosstalk is smaller than -20dB in the 1.5μm ~ 1.7μm range. For the length of the couplers is 7mm, we find that the crosstalk is smaller than -35dB in the 1.5μm ~ 1.7μm range. The same as the requirement of the maximum crosstalk, the corresponding wavelength is between 1.42μm to 1.7μm when the lenght of the couplers is 12mm.

The influence of the position and the length of the Bragg grating written into conventional 2×2 fused couplers on its spectral response is numerically investigated and analyzed. It is possible to realize optical add and drop multiplexers with conventional fused couplers as well as with photosensitive couplers, and there is an optimized position and appropriate length of grating to obtain high reflectivity from drop port. In order to improve the characteristics of the component, a nonlinear chirped grating is proposed to be written into the coupler. According to the parameters in simulation, component with larger than 10dB reflectivity and bandwidth >1nm is obtained by inscribing a uniform Bragg grating in fusion region of the 3dB coupler experimentally.

Based on discussing the coupling characteristics between two curved waveguides, an improved directional coupler is presented, namely, substituting two curved waveguides for the straight waveguides used in the conventional directional coupler. The FD-BPM, based on PML (perfectly matched layer), is applied to analyze the relationship between the insertion loss, power loss and the separation between the waveguides in the coupler region both the conventional and improved one. Configuration parameters of 3-dB couplers are worked out according to two kinds of directional couplers mentioned above. To achieve wavelength-flattened response, an asymmetric structure is also used. The configuration and performance of improved directional coupler has improved obviously, compared with the conventional one.

This paper represents the testing of grating spectral intensity distribution and describes the testing of semi-split beam grating of DVD. Then some methods to improve the stability of the data are introduced.

We have succeeded in transmitting the signal as long as 1400km with G.652 fiber using chirped fiber gratings. Asymmetrical apodization was adopted to reduce the grating’s GDR (group delay ripple). Power and dispersion management was adopted here to suppress the nonlinear effects.

Nonlinear chirped FBG(NLCFBG) is found to have the performance to compensate the dynamical nonlinear dispersion. In this paper, we investigate and compare, for the first time, the reflection spectrum and group delay of apodized nonlinear chirped fiber Bragg gratings which has raised much interest because of its reduced reflectivity sidelobes in dynamical status. The dispersion characteristics of apodized, nonlinearly chirped fiber Bragg gratings and their potential as dispersion compensators have been studied systematically. It is shown that the super-Gaussian profile and Cones function result in an overall superior performance, as it provides highly quadratic group-delay characteristics in the dispersion-slope compensation.

The main characteristic affecting on fiber transmission are attenuation and dispersion in optical fiber. The equipment of measuring attenuation has been set up in this letter. The attenuation in some organic optical fiber is measured. The lowest losses are 238dB/km at 670nm for PS core, 197 dB/km at 580nm for PMMA core, and 0.2dB/m at 650nm for C₆H₆ liquid-core optical fiber. Temperature and ultraviolet radiation affecting on loss in fiber are researched.

A novel technique is proposed for pulse compression by utilizing the nonlinear interaction between two neighboring pulses in optical fiber. By using the method of split-step Fourier (SSF), we numerically investigate the propagation of the pulse pair in optical fiber. Usually, two pulses attract each other and collide into one compression pulse periodically along the fiber. So with an appropriate choice of the fiber length-the collision length, such a fiber can act as compressor, so-called nonlinear action compressor. And then, the effects of parameters on the compression pulse have also been investigated numerically with SSF and we find the quality factor Q_c>1.

First, in order to get the low-loss and small-size 2-arc S-shaped bend, the lateral offset between waveguides with different curvature was optimized to reduce the mode mismatch. To get the smoother S-shaped bend, which also has the overall bending loss as small as possible, another S-shaped bend based on functional approximation theory of B-spline was put forward. By this means, the transition loss at the junctions can be completely eliminated and also make the pure bending loss as small as possible. A comparison among sine-generated, cosine-generated, 2-arc and numerical calculated S-shaped bends was also been conducted. Using Beam Propagation Method (BPM) and analytical method, the result was verified and good agreement was got.

Optical waveguide array are attractive for high-speed, wide-angle optical beam steering or deflection, but optical waveguide arrays radiate undesirable sidelobes. It is shown that suppression of sidelobes can be accomplished by configuring array elements in nonuniform pattern. Tow kinds of arrangement of linear changed spaced optical waveguide array are discussed. Sidelobes can be suppressed deeply. Especially, the light path area ratio can be improved to 71.9% by using symmetrical structure array. Steering characteristic shown that the maximum steering degree of 24⁰(-3dB) can be obtained by nonuniform spaced optical waveguide array.

This paper reports a new type of integrated hybrid component. It integrates the function of polarization beam combiner, isolator and depolarizer as a unit. Characterised small dimension, high isolation, low insertion loss, good depolarization effect and high reliability, it is specially designed for Raman amplifier. The packaged dimension is 75x5.6x5.6mm³. The main optical specifications are insertion loss ≤0.6dB@1450±40nm, isolation≥30dB and DOP ≤10%.

Based on the programmable phase modulation technique with a multi-channel optical wave-guide array, a novel method used for collimated laser precision scanning was presented. Optical system and control circuit have been designed for the multi-channel optical wave-guide array. Theoretical analysis and experimental result shows that the method can be used for small angle adjusting and big angle scanning of collimated laser in free space light communication.

The optical variable attenuators (VOA) play important roles in wavelength division multiplexing (WDM) transmutation systems, this paper describes a new type variable optical attenuator made by using fiber U-grooves in silicon wafer and polymer-network liquid crystal. Fibers are placed in the U-grooves of silicon wafer, and the polymer-network liquid crystal is filled in the gaps between the ends of the docking fibers. The paper explains the principle of the attenuator operation and presents experimental method in laboratory.

In this paper we investigate both noise and transmission performance of bi-directionally pumped Raman amplifiers (RAs) in longhaul WDM systems detailedly. Compared with backward pumping or Raman+EDFA hybrid amplification, bi-directionally pumping can provide flatter OSNR spectra in wideband WDM applications, as well as better noise performance at identical nonlinear phase shift due to its uniform power distribution. Moreover, transmission impacts induced by SPM and XPM are also analyzed, which indicates that Raman amplified systems are more sensitive to dispersion maps than discrete amplification.

The generic features of modulation instability (MI) in optical fibers are disclosed by application of an extended nonlinear Schroedinger equation. The role of arbitrary higher-order dispersions, stimulated Raman scattering (SRS) and self-steepening (SS) in MI is identified. It is shown that all odd-order dispersions contribute nothing to MI, whereas all even-order dispersions not only affect the conventional instability regions but may also lead to the appearance of new MI regions. In the presence of SRS, the MI gain spectrum in optical fibers consists of two parts: the conventional MI gain spectrum and the Raman gain spectrum. In the case of normal dispersion, MI occurs due to SRS. In the case of anomalous dispersion, as the initial power increases, the SRS gain spectrum is gradually screened from the conventional MI gain spectrum. Self-steepening exerts little influence on MI in both normal and anomalous dispersion regimes. Numerical simulation confirms the obtained analytical results.

Based on matched fiber grating interrogation scheme, a fiber grating strain sensors system has been proposed and experimentally demonstrated on an equivalent-strength cantilever beam model, which can be deployed for civil structural strain and mechanical vibration simultaneous detection. Through special designing of sensor head, the temperature cross-sensitivity in strain sensing has been automatically removed. A common-path reference measurement structure has been used, so measurement errors caused by fluctuation of losses in the system or the light source power has been effectively eliminated, and the long-term stability of sensor system has been improved.

In this paper, we propose a novel all-fiber variable optical attenuator based on high birefringence fiber loop mirror. Part of the birefringence fiber was pasted onto an equivalent-strength beam and by applying a strain with a high precision screw thruster on the free end of the beam, we observed that the transmission spectrum of the fiber loop mirror shifted with nearly unaltered shape. The attenuation at 1551nm is more than 30dB with about 6dB insertion loss. By tuning the angle between the fast or slow axes of input and output planes of the birefringence fiber, the insertion loss of this VOA can be minimized to no more than 1.5dB. The wavelength shift of this VOA varies linearly (the linear correlation coefficient reaches 0.9979) with the deflection of the beam and it turns out good attenuation characteristics.

In this paper, we successfully demonstrated automatic PMD compensation in 40Gbit/s NRZ transmission for the first time. Using a PMD monitor of 20GHz intensity extracted from the receive 40Gbit/s NRZ base band signal, we accomplished the feedback control of an optical PMD compensator consisting of a polarization controller and a polarization-maintaining fiber. And we report the statistical assessment of an adaptive optical PMD compensator at 40Gbit/s. The mitigator, described in, is experimentally tested in many PMD conditions (not limited to first order) covering Maxwellian-like PMD statistics. Experimental results, including bit error rate measurements, are successfully compared with theory, hereby demonstrating the compensator efficiency at 40Gbit/s. Furthermore, this letter introduces a two-stage PMD compensator. Our experimental results shows that, the compensators based on the two-stages of compensator can be used to PMD compensation in a 40Gbit/s OTDM system with 60 km high PMD fiber. The first-order PMD was max.274ps before PMD compensation. It was smaller than 7ps after PMD compensation. At the same time, the tunable FBG have a function of dispersion compensation.

We present a novel model using Jones matrix method to describe the temperature dependence of high-birefringence fiber. We also apply the model to a temperature dependent PMD emulator with 12 sections of HiBi fibers directly spliced at fixed orientations. From numerical simulation and experiment, we get ideal DGD statistical distribution, second order PMD statistical distribution and the frequency autocorrelation function.

In an earlier approach, the 2-D acoustical field profiles on the substrate region are often calculated with BPM. In this paper, we present a new approach based on the finite element - artificial transmitting boundary method and calculate the 2-D acoustical field on the substrate region.

We investigate wavelength conversions based on chirped optical superlattices, such as linearly chirped and sinusoidally chirped optical superlattices, through cascaded second-order nonlinear processes for wavelength division multiplexing application. They are compared with periodic optical superlattices in terms of bandwidth, efficiency and response flatness. The sinusoidally chirped optical superlattice shows more excellent overall performance than the periodic and linearly chirped optical superlattices.

As GeO₂ concentration increased, residual stress increased. For the same tension, axial stress induced by drawing is linearly proportional to GeO₂-dopant concentration. The residual stress of the fiber (about axial direction) is originated from phase distribution caused by photo-elastic effect: A phenomena that a fiber becomes birefringent through the nonisotropic stresses. The photo-elastic effect makes phase shift such that intensity difference of light is appeared. The phase profile is obtained by measuring the intensity difference. And phase profile can be converted to the stress profile by Abel transformation. The magnitude of stress induced by drawing tension, is different as glass material constitution. As material is the more viscous, induces the more stress. Generally the glass for which dopants such as Ge, B, P and F are added has lower viscosity value compared with pure silica glass. And as dopant concentration increased, viscosity decreased. We investigated the relation between GeO₂-dopant concentration and the magnitude of residual stress. Perform core was deposited with Ge-Si ratio having parabolic increment about radial direction. GeO₂ concentration of core varied from 0 to 21.67mol%. That was also described to index change. The index difference (delta N) of core and clad was 0.026. The preform was drawn for fixed tension. Residual stress of optical fiber was measured after drawing. And fiber was fully annealed by flame. After then stress was measured one more. We obtained stress as the difference these two data: before and after anneal process. In fiber drawing process, tension was differently applied for each point of core region so that the measured stress about radial direction was not correct. To compensate the error, stress of sample was referred to pure-silica rod of that.

Base on the theory of the thick grating, volume phase grating (VPG) is analyzed numerically in light of thick grating theory and the characteristics of VPG’s gain spectrum in connection with the variation of parameters are presented, based on which a novel dynamic gain equalizer (DGE) is designed. Simulation shows that the DGE designed can work well.

All-optical logic gate based on MMI (Multi-Mode Interference) is proposed in this paper. Different from other methods, MMI efffect is utilized for the logic functions including AND, OR, NOR, and XOR. All-optical logic function is realized at specific output waveguides in accordance with the control signal condition.

In the present study, we report the design and development of a cost-effective, simple, sensitive LED - based fiber optic sensor for detecting trace amounts of chloride ions in water. A multimode plastic clad silica (PCS) fiber with the cladding removed and long period grating (LPG) written on its middle region acts as the sensing element. Exposure of the sensing region to water samples containing spectroscopic reagents for the detection of chloride ions causes evanescent wave absorption, which increases with increase in concentration. The limit of detection of the sensor is found to be a few parts per billion and the operational range covers more than five orders of magnitude.

TE/TM mode converter is a key element of integrated acoustooptical tunable filter (AOTF). Employing SiO₂/In₂O₃ film as acoustical waveguide can suppress sidelobes effectively and simplify fabrication technique in integrated quasi-collinear AOTF. In this report, the eigenvalue equation and the field solution of such configuration has been obtained by using modified Wenzel-Kramers-Brillouin (WKB) method. The results are compared with those by using vector finite element method (VFEM). When the optical waveguides are covered by such oxide film, the difference of mode indices of both polarizations and the effective propagation velocity of surface acoustical wave (SAW) will decrease, and these decreases lead the shift of optical wavelength, which mainly results in the change of the former.

The impacts of PMD on optical fiber transmission system are investigated briefly. A new compensation scheme is proposed using a single compensator in multichannel systems to compensate several channels at the same time. The DOP of the received signal requires no high-speed circuit and is independent of bit rate. In the proposed scheme the DOP of the optical signal is used as the control signal, and the maximized DOP is fed in polarization controller.

The dispersion and self phase modulation is two important factors of the limit transmission distance in optical fiber communication. A novel method for measuring the dispersion slope of a long single-mode fiber was reported. By asymmetric modulation and Mach-Zehnder interferometer, the interferometer causes counter propagating wave to travel in test fiber with different propagation constants. We introduced the fast Fourier transform technique, the autocorrelation function is brought forward, and the information of the interference fringe is analysis with high speed so that the accuracy of signal is estimated. Successively, the experiment was performed on the test fiber to determine the nonlinear refractive index and self phase modulation, exact pulse bandwidth solution is presented. We found that quantity was depends on the intensity of incidence light and the peak power, and the frequency spectrum is broadening clearly. The result shows that the intensity input and the peak power can affect the phase shift value.

PMD is a crucial limiting factor in many optical transmission systems as the data rates increase to 10Gbit/s and beyond. In this paper it is derived that a simple and exact analytical expression for pulse broadening in the optical fiber transmission system suffering from polarization mode dispersion, and then analyzed the transmission performance of NRZ, RZ, DMS and CRZ. It is educed that PMD has smaller impact on CRZ.

For the first time, we study the transmission performance of 10Gbps PRBS data stream over ultra-high polarization mode dispersion (PMD) dispersion compensating fiber (DCF), which PMD coefficient is 237.95ps/km^1/2. The simulation has been done by coupled nonlinear Schrodinger equations. Also transmitted experiment has been done by DCF with a PMD coefficient of 237.95ps/km^1/2. The result of the simulation is consistent with that of the experiment.

The multi-wavelength liquid signature analyzer (MWLSA) is used to analyze the characteristics of liquid. It adopts two kinds of transmitter diodes with different peak wavelengths as the light sources of the system. With MWLSA not only the light intensity signal reflecting the optical characteristic of the sample liquid under different wavelengths can be obtained, but also the volume and outline information of the corresponding liquid drop are acquirable. The application of the multi-wavelength light sources makes it possible for us to get more information about the liquid sample, which enriches the function of the liquid signature analyzer and improves its discrimination ability of different liquids so as to have more application fields.

When the long period fiber grating (LPG) is surrounded with dielectric material whose refractive index is higher than that of cladding, core mode to radiation mode coupling occurs. In this paper, a theoretical method to analyze the radiation-mode resonance in LPG is presented. The coupled-mode equations of LPG are derived based on Amnon Yariv’s coupled-mode theory. Here, the radiation-mode theory is used. The electric field of individual radiation mode is given based on the weakly guiding approximation of three-layer optical waveguide. The expansion of the total radiation modes, which is a Fourier-Bessel integral, is presented. It’s noted that the weight of the integral is not one. The normalization of the individual radiation mode is discussed in detail. It’s found that the normalization integral is unbounded but changed to a Dirac function. Thus, it’s calculated only through theoretical derivation. The approximate numerical method to deal with the coupled-mode equations is presented. The transmission spectra of LPG, which are surrounded with several surrounding refractive indices, are numerically calculated.

A Hi-Bi linearly chirped fiber Bragg grating is written into a polarization-maintaining photosensitive fiber by UV-beam through a linearly chirped phase mask. Its performance as group velocity dispersion and polarization mode dispersion compensator is demonstrated in 10 Gb/s fiber-optic transmission systems.

A temperature-tunable polarization interference filter (PIF) made of YVO₄ crystal has been presented and applied for wavelength monitoring of a distributed feedback (DFB) laser in a dense wavelength-division-multiplexing (DWDM) optical communication system. This novel device offers a flexible way to monitor the operating wavelength of the transmitter over a wide capture range. Monitoring resolution of 0.02 nm can be obtained by measuring the temperature variation of the filter while its transmission value is kept at a constant value.

In this paper, we propose a novel method of the demodulation of FBG sensing system based on chirp grating and LPG edge filter in which chirp grating is used as band filter. The measurement speed is mainly determined by the response time of the photo-detector and the convert time of AD chips. So, it can highly improve the stability and scan speed of the sensing system. In the experiment system, we use fiber Bragg grating and adjust its bandwidth to get a chirp grating.. The center wavelength of chirp grating is 1551.60nm, and the pass-band wavelength is 7nm. The LPG is written on a standard single mode fiber with microlens array. The grating has a period of 440μm and a length of 3 cm. The center wavelength of LPG is 1558nm, and the falling edge of LPG is from 1540nm to 1555nm. We investigate light power by using a monitor magnify circuit, while the reflected wavelength of FBG by using optical spectrum analyzer. This system has high linear output and the linear fitting is 0.9918. The windage is due to the non-perfect square spectral profile of the reference chirp fiber grating.

In this paper, we focus on the improvement of accuracy of phase-shift methods to measure the fiber dispersion. By the analysis of experiment results and possible error sources, the more suitable measurement conditions are provided to decrease the measurement error to a great extent. Except keeping a constant temperature and isolating the device from mechanical vibrations when measurement is carried out, as large as 1nm measurement wavelength step and large wavelength span at several tens nm level are preferred to obtain more accurate and repeatable measurement.

An integrated grating-assisted optical add/drop multiplexer (OADM) based on an innovative phase-compensated coupler is proposed. This device can get high performance, while the grating is not needed to be critical positioning. Therefore, it can be fabricated with feasibility.

The proposed methods of Polarization Mode Dispersion (PMD) mitigation can be divided into three main approaches: (i) electrical PMD compensation, (ii) optical PMD compensation, and (iii) mitigation by use of robust modulation formats, increased power margin etc. In this paper, we discussed each of these sententiously, with less emphasis on comparing the first and the second, but with more emphasis on the third. We quantify the benefits of using different techniques for compensation of PMD in fiber-optic communication systems by means of numerical simulations. This is done both with respect to PMD-induced pulse broadening and in terms of system outage probability for different data formats [nonreturn-to-zero (NRZ) and return-to-zero (RZ)]. With our experimental results, we find that RZ performs better than NRZ, furthermore, it is comparable with 2-3 DOF PMD compensator, and can be expected to be a practical alternative in particular if used in combination with error correcting codes. We also study the trade-off between power margin and acceptable PMD. Moreover, it is generally believed that a PMD compensator with a polarization controller and a variable delay line can only compensate the PMD to the first order. Our experimental results show that, the counterintuitive fact that this scheme can also partially compensate for higher order PMD. We also investigate the benefit of using a polarizer as compensation element where the optical average power can be used as a feedback signal.

EDFAs are broadband optical amplifiers, which are increasingly replacing conventional optoelectronic regenerators. In high-speed data transmission they have to be designed for low polarization dependence to prevent a rise in the bit error rate. Long links like undersea or transcontinental cables contain many EDFAs, this way multiplying their polarization dependencies. Therefore, EDFAs have to be characterized carefully for polarization mode dispersion (PMD) and polarization dependent gain (PDG). In this paper, the PMD measurement is achieved with a modified Stokes vector method. In this method, the polarization controller is used to generate a number of input polarization states, all of which arelocated on an unit circle on the the North Pole of Poincare sphere. For each state, a small wavelength step is applied. Using the Polarization Analyzer, the arc on the Poincare sphere, which is caused by changing the wavelength, is determined. The arc is known to vary sinusoidally with the input polarization state. The widest arc is the measure for the PDG. The measuring system includes HP8164A Tunable Laser, HP8509B Polarization Analyzer, HP 8169A polarization controller and HP8153A Power Meter etc. Four dedicated polarization states (0° lin., 45° lin., 90° lin., circular) are set and the power without device-under-test (DUT) is measured. Then the EDFA is inserted and the power is measured again. This delivers the first row of the Mueller-Matrix from which the PDG can be calculated.

The transmission spectrum of the phase-shifted and apodized long-period fiber grating with different parameters is calculated and analyzed based on the fundamental matrix approach. This paper presents the design method of phase-shifted optimum, which uses the nonuniform phase-shifted method to optimize the transmission spectrum of long-period fiber grating. Compared with uniform phase-shifted and apodization method, this method can effectively remove the sidelobes near the resonant wavelength. The calculation and analysis results show that it is an effective design method compared with the design method of apodization optimum.

Photonic crystal polarization maintaining optical fibers(PC-PMFs) could offer much higher birefringence than conventional PMFs and have many remarkable properties. In this article, the localized function was orthogonalized with another function for the PC-PMFs, so the orthogonal localized functions were got, and the mathematical model of modal birefringence for PC-PMFs was brought forward. What’s more, a mathematical formula of attenuation for PC-PMFs was made, the effecting factors on the attenuation of PC-PMFs were analyzed and the process technologies to decrease the loss of PC-PMFs were also proposed.

Erbium doped fiber amplifier have been demonstrated at several wavelengths. The exceptionally broad and intense absorption spectrum of erbium with other rare-earth co-doped fiber is advantage in high power amplifiers and fiber lasers. In order to broaden amplifying band, it is important to modify spectrum properties of erbium doped optical fiber. In this dissertation, erbium with ytterbium, thulium and Lanthanum co-doped fibers were fabricated by MCVD. This paper focus on the influence of concentration and ratio of rare-earth on spectrum properties of fiber. It was found that absorption of the EDFs was affected by erbium concentration and ratio of erbium and other rare-earth. Absorption band were broadened by adding dopant of other rare-earth.

Optical fiber cables installed in seabed were divided into the deep water optical fiber cables and the shallow water optical fiber cables (SOFC) in the light of the depth of installation. Shallow water optical fiber cables, belonged to submarine optical fiber cables, are used in not only the connection among the islands and the channels but also the extend lines of land telecommunication. The shallow optical fiber cable presented in this paper is mainly used in Guangdong Province. Some main technology characteristics of cable and the test results are introduced in this paper. Simple structure, lightweight and fine performances are the peculiarity of this shallow water optical fiber cable.

Apodization is the key technique to improve the performance of Chirped Fiber Bragg Grating (CFBG). In this paper, the theoretical analysis on apodization by dithering method is presented. For comparison, CFBGs are manufactured respectively in dithering and scanning method, while employing the same apodization function. The result shows the former is more competent for its outstanding characteristics such as symmetrical reflection spectrum, low group delay ripple, and flexibility.

For its low cost and high quality properties, wavelength division multiplexer based on arrayed waveguide grating is used widely in optical communication components and systems. For the purpose to reduce the cost and improve the quality of communication systems, wavelength division multiplexer with wide and low crosstalk is necessary. In this paper, a new wavelength division multiplexer with wide pass-band and lower crosstalk is designed, where special tapered couplers with split structures are used as input waveguides, and experiment results shows that the transmission with wide pass-band and lower crosstalk could be obtained.

Electromagnetic(EM) energy can propagate along optical waveguides made by using the dependence of surface plasmon polaritons(SPPs) on nanometer gap width between two parallel metallic plates. Finite-difference timedomain (FDTD) was employed to calculate the propagation constant of this nanoscale metallic waveguide. The agreement between the calculated values and results predicted by the theory of metallic waveguide is quite satisfactory. We then demonstrate a branched structure with right-angle bends and structures that can be used as nanoscale interferometers by using the ideal of nanoscale metallic waveguides. EM energy transfer was simulated in these structures by using FDTD method. The results show that bend and insertion losses both remain at an acceptable level. We also simulated EM energy transfer in nanoscale metallic waveguide arrays. It is found that the energy spreads into two main lobes as the light propagates along the waveguides. The separation angle of the two lobes is determined by the period of the array.

A new type of communication optical fiber with S+C+L-bands was introduced in the paper. This optical fiber is designed for the application of DWDM system on S+C+L-bands. The effective operating bands can be even extended to E-band and L⁺-band. In order to reduce non-linear effect, such as FWM (four-wave mixing) etc., the minimum dispersion coefficient from 1460nm to 1625nm of the optical fiber is greater than 2ps/nm km, and the effective area at 1550nm is around 60μm². Low dispersion slope is helpful to reduce the cost of dispersion compensation for high bit rate DWDM system and maintain a moderate dispersion value over S+C+L-bands. The dispersion slope of this type of fiber was optimized not to be less than or equal to 0.038ps/km nm² (over C-band ), the dispersion coefficient isn’t higher than 11.4 ps/nm km at 1625nm. By the optimization of manufacturing process and precisely designing on index profile, excellent attenuation and PMD performance were obtained. Attenuations at 1550nm and 1625nm are less than 0.24dB/km, PMD co-efficient is less than 0.05 ps/km1/2.

We report a plastic holey fiber that has a strongly anisotropic structure. The polarization property of this microstructured plastic fiber was investigated. The result shows it has a high birefringence.

A pressure and temperature sensing system based on fiber-optic Bragg grating sensors for the oil and gas downhole is reported in this paper, the weak pressure sensitivity is enhanced and the cross-sensitivity of temperature and pressure measurands is overcome by an optimally designed mechanical enhancing and compensating structure, the working principle, experimental setup and testing results are also given.

In the paper, a simple and effective FBG sensor able to discriminate temperature from strain at a single point had been worked out, by sticking half of it on the fixed end of the polymer equivalent beam, leaving the other half free. The FBG was then separated into two segments with different temperature and strain coefficients, which composed the measuring matrix. The measuring sensitivities of temperature and strain of our setup are 9.58×10^-6(1/°C) and 6.72×10^-7(1/με) respectively. This device will have wide applications to discriminate between strain and temperature of sensing networks.

DCF optical fiber Stokes Raman forwrad scattering and backward scattering gain spectrum have been measured by Raman laser as a pump source and high spectral resolution four grating spectrometer. There are 15 phonon modes in the Stokes forward scattering region and 18 phonon modes in the Stokes backward scattering region. In the low frequency region, there are 3 characteristic phonon modes they are 41.4 cm^-1, 68.0 cm^-1 and 96.7 cm^-1. The characteristic Raman peaks of DCF fiber is 434.7 cm^-1 and 455.4 cm^-1 that are correspond to 440 cm^-1 and 490 cm of normal single mode fiber as a function of pump power has been measured. Measured DCF Raman gain spectrum is different from that in common reference and books. The reasons are the high Ge0₂ concentration in DCF fiber and the developing of measuring technology.

In this paper, we present a new numerical method for calculating pump power in designing multi-wavelength pumped Raman amplifiers, by using some optimal searching method, we establish a complete computing model to optimize the pump wavelength and power allocation with flat net gain and broad bandwidth. In order to increase precision and degrade computing time a new predictor-corrector linear multistep method is proposed instead of one-step method, which was adopted in traditional designing to calculate power integral for signals and pumps propagating through the fiber. Further more, we adopt the Quasi-Newton iteration method to adjust the pump power efficiently without any manual adjustment. The optimal results show that by using our method, iteration process will be convergent rapidly and relative gain flatness below 5% can be achieved over 100nm bandwidth without any gain equalization devices. The whole optimal method costs within 10 minutes in a common computer.

In this paper, a novel fiber Bragg grating (FBG) temperature sensor system with low cost demodulation mechanism was proposed. The broadband light source was demodulated by a long period fiber grating (LPG) with an appropriate attenuation band. The sensing FBG was encapsulated with aluminum groove to make the FBG have a higher thermal expansion coefficient. The sensor with enhanced sensitivity 0.02°C was realized.

With increasing bit-rate polarization mode dispersion (PMD) is becoming major system impairment. As the birefringence of a fiber changes randomly along a fiber link and the state-of-polarization (SOP) of an optical signal changes with environmental conditions, PMD effects on the data signal are stochastic and time varying. Consequently analysis of impairment caused by PMD is difficult. In order to assess the PMD impairment in optical transmission system, a great many of samples of the systems under different conditions have been studied previously. The former studies have been shown that PMD-induced system impairment depend on many transmission factors, such as modulation formats, receiver characteristics, etc. Recently the effects of transmission characteristics on PMD impairments have been taken into account. In this paper, we take these effects into account together for the first time to our knowledge. Firstly we show in both experiments and simulations that the imperfection of transmitters, primarily timing and amplitude jitters, could significantly increase the PMD-induced penalty in optical fiber transmission systems, especially when the instantaneous DGD is large, which is relevant situation for outage occurrence. Then we introduce a novel method to analyze the effects of transmission and transmitter imperfection on PMD impairments synthetically. Furthermore, we try to establish a new standard of estimating the PMD impairments.

An experimental setup was established by using a high stability, narrow line bandwidth fiber laser with a fiber optic amplifier, polarization maintaining fiber coupler with split ratio of 50:50 and 95:5 respectively, a fiber optic sensing coil with high birefringence large nonlinear polarization maintaining fiber, and uniform fiber Bragg grating that was used at output port for filtering the excess pumping component. Based on this experimental setup, the threshold power of the pumping laser was deduced, and the relationship of the spectra and intensity between pumping laser component and stokes component with frequency downshift was obtained experimentally.

A novel method to mechanically induce a long-period fiber grating (LPFG) by a grooved plate is reported. The transmission spectra of this kind of grating under different pressures and some special LPFG’s are experimentally investigated. This method is simple and reconfigurable and offers large spectra tunability. This type of LPFG has potential applications for gain flattening in erbium-doped fiber amplifiers (EDFA) and for filter design.