In the present world, the demand to support different types of nationwide traffic (data, voice, video, etc.) requires a high bandwidth and a suitable network topology. Optical fiber offers the potential to supply a pool of capacity to be shared among users and can meet the demands. In this paper, we propose a network topology which serves the above purpose and a routing algorithm which fully deploys the advantages of the topology. The proposed Multi-Dual Ring Connected Shuffle Network Topology, which can be easily implemented with Wavelength Division Multiplexing and a multi-hop approach, can eliminate the traffic bottleneck of existing optical communication networks. The proposed adaptive self-routing algorithm can disperse packets away from `trouble' portions of the network should a congestion or a link failure occur, this makes the traffic distributed as evenly as possible among all the communication channels available and makes the network survivable. The routing scheme, which does not require a priori knowledge of the traffic pattern, can exploit the full potential communication bandwidth of the proposed network topology. It has the benefits of adaptive routing schemes but adds virtually no extra costs. Since the routing scheme is very simple and the switching can be done `on the fly', the proposed network architecture can be a good candidate for the backbone of Information SuperHighway.

The working principles and current status of various high speed (approximately ns) tunable filters/receivers have been received for applications in broadband switching networks. Directional coupler based channel drop/add tunable filters/receivers have been discussed in detail.

A novel design for multimode 1 X 2 and 1 X 4 splitters is proposed. These devices differ from conventional 1 X 2 and 1 X 4 multimode interference splitters, as they do not rely on the interference between the excited modes propagating in the multimode region. Instead, their functionality is based on the principle that in an asymmetric multi-pronged splitter, the power in each excited mode can be directed unambiguously into one of the single- mode output channels with minimal cross-talk between channels. The geometry and relative position of the single- mode input waveguide of the 1 X 2 and 1 X 4 splitters is optimized to split the input power as evenly as possible between the two and four output channels, respectively, and to minimize the excess loss of the device. A simple low- power single-mode tap, based on the same principle, is also investigated and its excess loss and wavelength dependence determined.

In consideration of better confinement of optical field and integration with practical communication network of optical fiber, we proposed a novel vertical (Delta) (kappa) directional coupler switch with inverted rib waveguides made of nematic liquid crystals (NLCs). Because of the large birefringence of LC's, a very short switching length, about 60 micrometers , is obtained; furthermore, the high extinction ratio, 25.73 dB, can be achieved in the 3D switch.

Light sources capable of emitting multiple wavelengths are key components for the implementation of wavelength division multiplexing (WDM) systems. Over the past several years, there has been remarkable progress in developing such sources. Today's WDM sources include solitary distributed feedback lasers selected by operation wavelength, tunable singlemode lasers, multi-wavelength laser arrays, and various integrated laser devices made with different technologies. This paper presents an overview of present WDM lasers, and discusses the pros and cons of the different fabrication technologies in conjunction with device performance, manufacturability, reliability and overall cost. Commercial availability of the lasers will also be reviewed.

We propose a wavelength-insensitive optical switch using twist nematic liquid crystal display (TN-LCD) panel for multi-mode or single-mode fiber communication systems application. Based on the simple and widely used TN-LCD structure, the optical switch has the potential advantages such as inexpensive, simple fabrication processes, and easy mass production. The preferable operating frequency of the device is 0.1 k to 10 k Hz ac wave. The critical and saturated voltage are as low as 3 Vrms and 5.8 Vrms, respectively. The high extinction ratio of 28.3 dB is obtained.

The purpose of this paper is to design a high efficiency waveguide, and it makes use of the mature theorem of channel diffused LiNbO₃ waveguide and a modified S-shaped structure. The advantage of the features offer a high coupling efficiency with fibers, larger lateral displacement and low transition loss. We have buried waveguide through indiffusion of a MgO layer for reducing the coupling loss. Further the concept of microprism-like structure is not only applied at the junction of the straight and bent waveguides, but also that is placed in the bent section. Some numerical results confirm that the design provides the better performance in the transition and bending losses.

In this paper, a free-space optical switching system capable of transferring (switching) digital optical time slots from one optical fiber to another is proposed. The design of the optical switch provides for the capability of switching soliton pulses from multiple fiber optic input ports to multiple fiber output ports. The parallel switching is achieved through the conversion of temporal information carried by the incoming fibers to spatial information using free-space optics and bistable optical resonators. The spatial information, containing time slots from different incoming fibers, is then switched by a switch that has a perfect shuffle topology and is implemented through free- space optics. The specific example covered here will give details of the operation and design of various sections of a 2 X 2 free-space soliton-based photonic switch. Limitations of the proposed switch, particularly with regard to the feasibility of its implementation, will also be discussed.

This paper presents a fast switching and gain control technique of optical repeated units for burst mode upstream transmission over a Super-PON system by using semiconductor optical amplifiers (SOAs). Measurement results confirm that switching of the SOA can be accomplished within 3 bits at 155.52 Mbps and that the gain control range is more than 10 dB.

A novel adaptive output selection scheme has been proposed for searching among a large number of multistable oscillation modes in a chaotic optical ring. The modes correspond to digital bit sequences, and the optical ring is potentially useful for generating digital optical signals. The adaptation is based on the collision avoidance between peaks in the oscillation pattern and pulses from another signal source. The collision signal is optically fedback into the optical ring and drives the system into a weakly chaotic regime until a fit oscillation mode which results in no collision in the output is obtained through chaotic mode transitions. Experiments have been performed using 21-bit oscillation modes and the results show that fit oscillation modes can be autonomously chosen with the proposed method. In particular, it was shown that the method can be successful even if the periods and pulse widths of the colliding signals are not the same and shown how the condition for successful collision avoidance can be determined in terms of the power in the collision pulses. Potential applications of the proposal in optical communication networks are discussed.

The proper combination of source linewidth enhancement factor (alpha) through electro-absorption modulator (EAM) and fiber dispersion coefficient D in wavelength division multiplexed (WDM) optical transmission systems can greatly extend the dispersion-limited system regeneration length L_reg (up to 70% for a 16 X 10 Gb/s X 400 km system). Four-wave-mixing-induced power penalty will only slightly increase due to the none-zero fiber dispersion, although more Erbium-doped fiber amplifiers are needed to compensate for the fiber attenuation. This scheme can also effectively suppress the modulation instability and self-phase modulation, etc. In general, when dispersion management or dispersion compensation measures are adopted for WDM systems using EAM with positive (alpha) , slightly over-compensation the fiber dispersion for all channels can effectively extend L_reg or reduce the dispersion-induced eye opening penalty if fiber nonlinearities remain tolerable.

High speed optical receivers have been fabricated by using p-i-n diode and distributed amplifier combinations. The high-speed p-i-n photodiode has been accurately modelled both electrically and optically. The preliminary experimental results show that the +/- 3 dB bandwidth from 1 GHz to 20 GHz was achieved for both input matched and unmatched configurations, while the later configuration shows its advantages by reducing the average equivalent input noise to nearly half the value of the former and increase the output power by 6 dB.

We have performed a study of the population dynamics in a composite, in which the active-medium is densely doped, by considering the near dipole-dipole interaction between nearest neighboring active particles. A model is presented to describe the particle-particle collective effects on the response time of the nonlinear refractive index in such a densely doped composite to an input optical signal. The results show that collective effects greatly enhance the magnitude of the nonlinear refractive index without changing the transient response time. This is expected to have potential in lowering the critical switching intensity of bistable switching devices without sacrificing switching speed. We examined two typical composites: rare-earth densely doped silica and perylimide-dye densely doped polymer/glass composites. It is found that perylimide-dye densely doped polymer/glass composite is more suitable for the switching application due to its large nonlinear refractive index and fast response time at relatively low optical intensity.

We discuss the development of tunable optical receivers for packet-switched multi-wavelength computer networks. The architecture of the tunable receivers consists of a planar waveguide grating demultiplexer, photodetector array and followed by transimpedance amplifiers with selection capability. The channel selection is based on sequential switching of the received optical signals in stages at the analog level. The receivers can accommodate 32 wavelength channels at around 1.55 micrometers region with channel access time of less than 40 ns.

Existing optical fiber and fiber-device fabrication techniques have been complemented recently by the development of plasma enhanced chemical vapor deposition (PECVD) processes for the fabrication of buried channel waveguides and associated devices. These processes rely on new forms of plasma reactors and diagnostic systems, which allow in-situ control of optical parameters such as refractive index, and are also being complemented by the direct writing of waveguides into photosensitive PECVD materials. Both the plasma and direct-write processes allow the fabrication of optical devices which are not readily feasible in fiber technology. The low-temperature PECVD process reported here offers the potential to integrate photonic devices with semiconductor sources and detectors to realize a compact, hybrid photonic-optoelectronic chip, complete with fiber pig-tailing. Because of their compactness and potential low cost, these types of photonic chips are attractive components for future high-capacity optical telecommunications and other networks now being planned as part of the information superhighway.

Bidirectional optical transmission over a single fiber is an important way to increase system's capacity. This paper will present the realization of practical fiber transmission systems based on a new generation of bidirectional optical fiber amplifiers (BID-EDFA), where the bidirectionality of the BID-EDFA is accomplished by using a WDM interference filter. Reliable bidirectional multi-span transmission at 2.5 Gb/s and 10 Gb/s has been achieved with significant system margins. The effect of system performance degradations caused by EDFA gain tilt and multi-path interference are discussed and methods of parameter optimization are outlined. Predicted and measured performances are compared and specific applications are presented.

Electro-optic modulators and switches are important components for photonic systems. Existing technologies (such as lithium niobate) have significant drawbacks in terms of coupling losses to fiber, photorefractive damage and cost. Silica, especially fiber, based devices would be ideal; unfortunately silica, being centrosymmetric, has no intrinsic bulk electro-optic characteristics. However an electro-optic coefficient can be induced by silica by poling. By thermal poling, an electro-optic coefficient of around 1 pm/V has been produced in bulk silica; whilst scientifically interesting, this is insufficient for practical devices, especially as the values for fiber are much smaller. Recent work on UV excited poling has produced values around 6 pm/V in fiber; sufficient to realize fiber devices a few centimeters long, requiring only a few volts for switching. To perform UV-poling, optical fiber with internal electrodes is produced by milling holes into the fiber preform, close and parallel to the core, and then pulling at sufficiently low temperature to avoid closure of the holes into which the fine wire electrodes are subsequently introduced. A voltage is applied to the electrodes to produce a strong electric field (approximately 100/V/micrometers ) in the fiber core which is also exposed to UV laser radiation. After removal of irradiation and field an electro-optic coefficient of around 6 pm/V is measured. By applying a modulating voltage to the internal electrodes this electro-optic coefficient may be used to effect phase or polarization modulation (and amplitude modulation in a suitable structure). Furthermore, by periodic UV-poling, electrically tunable in-fiber Bragg gratings may be produced. Details of the fiber and device geometry, the processing conditions, the measurement techniques, the device performance and potential applications of this exciting new technology will be presented.

Optical fibers are used extensively for the transmission of information and have largely replaced copper circuits for all but the shortest distances. They are capable of enormous bandwidth, very low transmission loss and minimal error rates. However whilst a range of passive fiber components is available to help exploit the fiber capability, much of the signal processing is still carried out electrically. This repetitive transformation from the optical to the electrical domains and back is obviously clumsy and inefficient. Fortunately active fiber devices also exist and the range of these is steadily increasing thus reducing the need for electrical intervention in optical systems. A new technology of integrated fiber circuits is emerging.

Recent studies on basic technologies including optical pulses generation and amplification for soliton transmission are reviewed. Demultiplexing for future OTDM soliton communication is also presented.

The amplified WDM optical fiber communication systems are developed in Peking University, Tsinghua University and Wuhan Institute of Posts and Telecommunications etc. in China. Some problems on the system technology are researched. A field trial of the system is under way.

This paper presents a four-channel, monolithically integrated laser diode driver array and its application in a multi-channel optical transmission link. The driver array is developed in the Tektronix SHPi bipolar process based on a P-type silicon substrate, to achieve a low fabrication cost and excellent performance. The combined features of the low driving threshold, flexible bias current and modulation current settings and low power consumption make the device suitable for parallel optical links. The developed driver array has an ECL compatible interface and is able to deliver a bias current of 0 - 20 mA and a modulation current up to 10 mA per channel. This device has been employed in a multi- channel transmitter module designed for optical interconnections. Two driver chips and an eight-element common-cathode laser diode array at 960 nm are mounted on a ceramic substrate on which a metal pattern is defined by thin film technology. The optical interface of this surface- mounting-type electro-optical module is a slanted polished fiber array (62.5/125 micrometers ) of eight elements. Measurements have shown a bit-rate up to 1.25 Gb/s per channel. This paper discusses the design approach and realization of the driver array and module, as well as their application.

In this paper, the effects of a reflected laser beam on DFB laser intensity noise and nonlinear characteristics are investigated. It is shown that reflected power increases the intensity noise to 5 or more decibels over the intrinsic laser noise level. The undulation of light output versus current (L-I curves) result from the optical feedback is discussed. The nonlinearity impairments induced by moderate levels of optical feedback is not as severe as evaluated by static L-I curves. Some effective methods to reduce the optical reflection are put forward.

In this paper, we present a novel method for analyzing the nonlinearity of the DFB laser. The method is based on a spectrum analysis with discrete Fourier transform on the model of laser mapping functions. In the view of the signal analysis, it avoids using some semiconductor parameters that are difficult to obtain but necessary for analyzing in the method. The algorithm together with the mapping function derived from the measurement can examine the harmonic and intermodulation distortions of laser chip and laser module. The comparison between the measurement and calculation shows that the algorithm is simple and effective for laser distortion analysis. The method is also applied to simulate the property of DFB laser and evaluate the linear request for the laser chips.

Here we report the LD pumped miniature 1.06 micrometers Nd:YAG solid lasers. Pumped by the LD of 1 W power, 420 mw of 1.06 micrometers CW laser has been obtained. The output stability is better than +/- 3%, and the divergence angle is smaller than 4 mrad. The volume of the device is very small and it is suitable to be applied in the optical fiber communication systems and optical fiber sensing system.

A permanent index change of 0.0051% was induced in Sm⁺²/Sm⁺³ doped aluminosilicate fiber by irradiating 2W of multi-line output from an Ar ion laser. The photosensitivity was detected by measuring a shift in LP₁₁ mode cutoff wavelength. Bleaching of a broad absorption band in the visible was also observed. The origin of the photosensitivity in the Sm doped optical fiber is the bleaching of Sm⁺² ion absorption bands enhanced by multiphoton processes.

The polarization effect of the all PM FOG is studied by using the Jones matrix theory on the first time. Above this study, the expression of the output noise is derived, which include the polarization degree (or extinction ratio) of the every element in the gyro system. The influence of each parameter on the detected polarization noise is theoretically analyzed, and an effective theory to reduce the detected noise is established.

In this paper, the stress induced birefringence of the all fiber PZT phase modulator was analyzed in detail, a method of `align axis' in manufacturing all polarization maintaining fiber PZT phase modulator was put forward and realized on the first time. Demonstrated by experiment, it can effectively depress the polarization noise on the output caused by the stress induced birefringence in the all PZT phase modulator.

This paper describes a new type of instrument which is used for on-line measurement of current passing through a lightning eliminator. Due to great magnitude range and extremely short transient process of the current, three sensors are separately designed to detect the current in three different stages. The modulated light signals are transmitted to signal processing circuits through optical fiber. A Microcontroller system with 15 Mkz sampling rate is designed to automatically record the wave form and some important parameters of the current.

This paper presents a unsymmetrical wavelength multiplexing system on the basis of concrete conditions to improve the image quality and resolution of fiber optics telescope. Different combinations of prisms and lens are chosen as long as wavelength multiplexing systems have identical line dispersion. Accordingly, if the magnification of the original fiber optics telescope is (Gamma) , only two prisms with 1 : (Gamma) angle dispersion ratio placed before objective and after eyepiece respectively can meet the above demands. In the fiber optics telescope we designed, the system's magnification is 2.8X. The two prisms' angle dispersion are 18'30' and 52'18' respectively. The angle resolution of the telescope is 23', and it is improved by 70 percent compared with that of the original fiber optics telescope.

This paper presents a new method for 2D image transmission using optical encoding through a row of optical fibers. The basic principle is to encode the 2D image in two different directions by wavelength-multiplexing encoding and time encoding respectively. As the two directions are incoherent, appropriate directions should be chosen to ensure the quality of the 2D image transmission. In this way, the information of the image can be transmitted overall through the fiber bundle. The transmission signal is pure optical and the channel capacity of optical fibers can be utilized more efficiently. Analyses and experiments show that the best image quality is achieved when the above two directions are vertical. In our experiments, the image transmitted through the row of optical fibers made of 500 fibers has more than 900 X 900 pixels, and the image color is undistorted.

Praseodymium-doped fluoride fiber amplifiers (PDFA) for 1.3 micrometers light will approach their practical applications to information superhighway if many outstanding device performance issues can be satisfactorily resolved. Efforts have been made to fabricate high quality praseodymium-doped fluoride fibers with a large NA (0.4), a low background loss (0.05 dB/m), a median strength (4%), and a good slope quantum efficiency (50%). Even better parameters are desired. Mixed halide glasses are studied as more efficient hosts for praseodymium. In this paper we propose an approach to combine the advantages of chloride in offering a good light amplifying environment for Pr³⁺ ions with the advantages of silica in offering good chemical protection and mechanical support to the chloride to make a new nanostructured material for 1.3 micrometers light amplifiers. In this approach praseodymium-doped chloride glass clusters of 10 nm sizes are compounded in silica host. In addition to the advantages of the composite material the gradient distribution of the clusters from the center and along one dimension of the composite material may result in the weldability of the material with the traditional silica fibers, which is preferable in engineering practice. Primitive samples were made and characterized.

An accurate analytical integral expression for coupling efficient between rectangular and circular optical waveguides is given with the help of coupled mode theory. The coupling coefficients for rectangular E^*₁₁ mode and cylindrical HE₁₁ mode between two parallel waveguides are calculated, the functional relation between coupling coefficient C^*_11.1 and normalized frequency V₁ for rectangular waveguide and normalized frequency V₂ for cylindrical step index waveguide is given, the corresponding curves for dielectric slab waveguide and optical fiber are also given.

An all-around research has been made for the properties of the polycrystal GeO₂ hollow-core fiber. Based on the transmission properties of this kind of fiber, a coupling system with three lenses has been designed for the first time, which ensures the practical application of these fibers.

Some conclusions have been drawn from the growth of KCl and AgCl optical fiber in the present paper. There is a temperature region with gradient near the solid-melt interface. The phase change latent heat is transmitted by the grown crystal. According to thermal transmission equation, the thermal conductivity (TC) in crystal, K_s, and that in melt, K_m, near the solid-melt interface affect strongly on the temperature gradient along the grown axis in crystal and melt. Generally, thermal conductivity in crystal K_s is greater than that in the melt, K_m. Similarly, K (metal) > K (nonmetal). TC of non-conducting crystal and metal will reduce with temperature increased TC in conducting liquid is 10 - 1000 times greater than that of non-conducting liquid. Halide ionic crystal with NaCl-type structure is nonconductor, whose TC K_s 1/T, in vicinity of melting point. However halid melt is conducting and its TC, K_m, increases as greatly as to transcend the value of K_g. Therefore the temperature gradient in crystal is inevitably greater than that in melt near the solid-melt interface.

The principle of tunnel coupling between single-mode optical fiber and thin-film waveguide and the designing method of the coupler are analyzed for light wave tunneling. A new structure of coupler is proposed, which has advantages of high coupling efficiency, integration and pragmatization.

The mathematical representation of modulation coefficient and intrinsic phase delay of PZT fiber-optic phase modulator are given. To study the temperature character, this paper design two measure system with a Mach-Zehnder and a Sagnac interferometer and get the experimental result curve which show that both parameters are linear with temperature approximately in set temperature range.

Fiber coherent bundles used in various instruments must provide for high quality image transfer. The primary defects, degrading the image quality, include the presence of broken fibers, which lead to troublesome dark dots in the view field, and so-called `grey' fibers (fibers have a partially reduced light transmission in the bundle). Both lead to a degradation of the local resolution capability of fiber-optic systems and to viewer discomfort who works with instruments in which these bundles are used. Such defects can be evaluated by the parameter-defect ratio, which is defined as amount ratio of defect fibers to total fibers. This paper describes a system designed for an objective and automatic evaluation of the defect ratio of fiber coherent bundles by a new method involving the image process.

Coupling efficiency is an important fact in optical fiber communication, it can be increased greatly by using an ideal Binary Optical Microlenses (BOML). Using phase balance method, we designed the BOML. The BOML's diffractive far field results was analyzed by the accumulating integral method. Properly coated for reflections, the lenses of the new design have theoretical coupling efficiency of 100%, and could excite 99.60% fundamental mode in the multi-mode receiving fiber and 99.95% coupling efficiency in the single-mode receiving fiber.

In this paper, we will discuss how to design a F-P filter and how to arrange channel spacing and one channel modulation rate, so that a WDM or FDM system has the maximum transmission data bit rate, in which the total utilized bandwidth at 1.55 micrometers wavelength is 4000 GHz.

For the first time, the spectral intensity distribution of the transmitted light of a F-P interferometer is derived considering the coherence length of the incident in this paper. The equations derived in this paper show that the transmitted light has the same spectral intensity distribution as the incident laser expressed. The frequency response of the F-P is different to the incident laser with different temporal coherence. The numerical calculations show that the minimum resolvable bandwidth of the F-P is always larger than the linewidth of the incident.

This paper deals with the optical fiber sensing system using light source modulation and circuit demodulation technology. Based on this technology, an experiment system is built for optical fiber electric field sensing. The results have been obtained from the experiment.

This paper reports the experimental results that near 100% peak reflectivity fiber Bragg grating have been fabricated by 248 nm KrF excimer laser irradiated a B/Ge co-doped fiber through a zero-order mulled phase mask and that the growth property of fiber gratings has been monitored using white light source and optical spectrum analyzer during the gratings formation. And we find that the evolution of the reflectivity of fiber gratings with exposure fluence can be perfectly fitted by power-law function of the form R equals cF^(beta ).

The use of linearly chirped fiber Bragg gratings with uniform coupling profile for compensating the dispersion of 100 km standard optical fiber link at 1550 nm are investigated theoretically for practical grating fabrication consideration. Numerical results show that a 40 mm long linearly chirped fiber Bragg grating with uniform coupling profile and optimal coupling strength can almost perfectly compensate the dispersion of 100 km standard communication fiber link up to 20 GHz. The dispersion delay curve of the fiber grating exhibits certain oscillation feature, and this does not significantly affect its dispersion compensation ability according to our calculations.

The non-confocal spherical mirror Fabry-Perot resonator is capable of having very high finesse and stability. However, the higher-order cavity modes (HOCM) of the non-confocal resonator must be controlled to attain any useful performance. Precision mode-matching collimators and/or an intra-cavity aperture is suggested and demonstrated here to diminish the HOCM. Mode-matching collimators at both input and output port of the resonator are recommended to achieve higher HOCM depression ratio, better long-term stability and a pigtailed in-line structure. A preliminary filter with mode-matching collimators at both input and output port of the cavity has shown a finesse of 100, HOCM depression ratio of 25 dB, insertion loss of 3.5 dB and a free spectrum range over 40 nm at 1.5 micrometers band.

This paper investigated theoretically the transmissions characteristics of three variants of fiber Fabry-Perot interferometers with fiber Bragg gratings (FBGs) as reflectors (FBGFPI) with respect to grating coupling coefficient, FBGFPI length, and fiber loss based on coupled mode equations and matrix method. The influences of facet reflectivity, loss and gain of fibers are also investigated.

Recently, for mass production supply the fabrication of fiber Bragg gratings with excimer lasers through a phase mask are popular everywhere. During this fabrication process the characteristics of near-field interference pattern play a significant role. In this work, by taking use of Rayleigh- Sommerfeld diffraction theory we calculated the intensity distribution of the interference pattern under different conditions. The analysis of result shows us that the distance of fiber with the phase mask and the divergent angle of the excimer laser dominants the main feature of interference pattern. A valuable suggestion was given out for producing higher quality FBGs.

In this paper, a 2 X 2.5 GHz to 2.5 GHz optical time division demultiplexer by using a kind of asymmetry nonlinear optical loop mirror was studied both theoretically and experimentally for the first time in China. The final extinction ratio was as high as 8 dB.

In this paper, an optical filter considered by a modified optical Mach-Zehnder interferometer has been theoretically analyzed, the expression of the transmission response function of the improved MZ optical filter was derived, and the characteristics were analyzed in details and discussed in comparison with those of the MZ optical filter.

A technique for fabrication chirped Er³⁺-doped fiber gratings with etching method is reported. An analysis is presented for the behavior of the chirped gratings as a function of wavelength, the angle between the illuminating beams, as well as the position of the gratings. Experimentally, Er³⁺-doped fiber gratings with variable period have been etched on the D-shaped fiber. Results obtained are in good agreement with theoretical analysis.

In this paper, wavelength control precision will be discussed when crosstalk is considered in a WDM or FDM optical fiber communication system. The control precision of an example, 16 * 2.488 Gb/s system with channel spacing (200 GHz) and the utilized F-P filter with FSR (6000 GHz) and F (300), will be calculated.

In this paper, the experiment results of Cs 455 nm Faraday Anomalous Dispersion Optical Filter transmission were given. The observation was discussed and analyzed.

An all-fiber filter based on quasi 2D photonic lattice has been proposed, which can be directly written in a multimode or single-mode fiber by the fabricating techniques of fiber gratings. Concurrently, an explicit method for analyzing the 2D photonic lattice is given. Numerical results show that this reflecting filter exhibits different properties from 1D photonic lattice (namely, fiber Bragg grating) with the same modulated strength of diffractive index. The possible applications of the all-fiber filter based on quasi 2D photonic lattice are also discussed.

Recently a four-beam Nd:YAG laser welding machine (Model JH- 4A) has been developed in this research institute for manufacturing the optical fiber communication devices such as coaxial diode laser modules, optical isolator etc. This laser welding machine is a four-beam synchronously welding system. The system is high positioning accuracy. The welded, devices have lower heat distortion and higher welding strength. The system well meets the OEM requirements.

Lately, in multigigabit-per-second lightwave transmission systems, emphasis has been laid on Polarization Mode Dispersion (PMD), and it looms as a potentially dominant source of pulse distortion in ultrahigh-bit systems. The measurement of PMD is realized in China for the first time and it is based on wavelength scanning method. The measured results of longer non-polarization maintaining fiber are fit to Maxwell distribution, and the measured results of many fibers made in China reveal that qualities of these fiber should be modified.

The thin-film polarizer possesses some merits that the crystal one has not, but the former is only suitable to a narrower wavelength range. In this paper the design and fabrication of the flat-type thin-film polarizer for communications of optical fiber are described. The polarizer what we fabricated has rather wide polarized wavelength region, rather high degree of polarization and good environmental stability. The isolation ratio is reached 30 db, and has less loss. The smallest external dimensions of the polarizer is 4 X 4 X 6 mm³.

Compression and broadening of picosecond pulses in dispersion-shifted optical fibers are reported by directly displaying the temporal profile through a CSA803 communication signal analyzer. 46 ps pulses at 1.55 micrometers generated from a gain switched distributed feedback laser diode were broadened or compressed to 65 ps or 35 ps in a 10 km-long dispersion-shifted fiber with dispersion parameter of +/- 2 ps km^-1 nm^-1, respectively. 41 ps pulses at 1.26 micrometers were distorted and broadened to 100 ps in the fibers.

Recently, emphasis has been laid on Polarization Mode Dispersion (PMD) in high speed lightwave transmission systems, and it looms as a potentially dominant source of pulse distortion in ultrahigh-bit systems. The measurement of PMD is realized by two novel methods--modified OTDR methods and modified S-38 methods. Their results are consistent with these from wavelength scanning method.

A performance analysis method of WDM optical fiber transmission system is proposed in this paper based on a semi-analytic approach. Here signal distortion caused by combined effects of fiber chromatic dispersion, SPM and XPM is obtained from computer simulation, while ASE noise and crosstalk due to fiber FWM are treated as additive Gaussian noise in the optical domain. An analytic formula for FWM noise power in a dispersion-managed system is also proposed. As an example, non-zero positive dispersion fiber and large negative dispersion fiber is used as transmission and dispersion compensating fiber respectively in a wide-real WDM network. Our results of performance analysis show that appropriate design of dispersion management scheme for the WDM network may achieve 4 X 10 Gb/s transmission over 2000 km with 6 dB power margin.

The character of linearly chirped fiber Bragg grating is judged not only the chirp ratio but also coupling profile. This paper numerically show that proper super-Gaussian coupling profile has more merits. The capacity of dispersion compensation of LCFBG can be improved when this aspect is taken into account.

We had put forward a scheme using a large nonlinearity and polarization-independent dispersion-shifted optical fiber in the nonlinearity loop mirror as an all-optical switching. So that, we can neglect the effect of fluctuation of states of polarization of signal wave or switching pulse wave. The characteristic of polarization-independent optical fiber is discussed in detail. Such a fiber will have a very promising future.

In this paper two problems associated with optical fiber AM CATV externally modulated transmitter are studied, one is effect of incident polarization on composite second order (CSO) and composite triple beat (CTB), the other is nonlinearity compensation of modulator's transfer function. We conclude that CSO deteriorates and CTB almost keeps unchanged when incident polarization drifting off TE mode and maximum deviation angle should be less than 6 degree(s) if CSO less than -70 dBc is demanded. We design predistortion linearity circuit based on Schottky diode and reduce CTB by 15 dB while having no effect on CSO.

The information format in the experimental underwater laser system is discussed. Two-pulse modulation for the laser is proposed. This method clearly reduces the modulated laser pulse's vibration range which is caused by the random change of Q switch's trigger of the laser. Thus the reliability of the communication is increased. The hardware and software flow chart of the modulator are shown in this paper.

It has presented a measurement approach for photo-devices impedance in this paper. We have designed and performed the special test fixture and standard for semiconductor laser diode chip impedance and achieved satisfying impedance calibration curves from 0.045 GHz to 5 GHz.

The frequency domain analysis for nonlinear distortion of 1.5 micrometers AM signal transmitted in single mode fiber is presented which drives, for the first time in our knowledge, approximate analytical solutions for composite-second order (CSO) and composite-triple beat (CTB) distortion. The results here can be applied conveniently to engineering, and are somewhat better than those given by Bergmann et al (1990), by Phillips et al (1991) or by Kuo (1993). All their expressions for CSO or CTB are dependent on a product of fiber dispersion coefficient times laser chirp rate, that causes a problematic inference fiber dispersion cannot cause nonlinear frequency distortion of pure AM signal (without laser chirping). Our expressions and curves for calculating CSO and CTB in practical CATV signal transmission at 1.5 micrometers are indicated, and also compared with the published theoretical and experimental results. Computation shows that pure AM signal suffers from fiber dispersion as well, the CSO and CTB of which are both proportional to second power of dispersion phase-shift angle, but proportional to first power and second power of AM index respectively. The curves of CSO and CTB versus transmission distance are also presented. It turns out that the results here include distortion effect of higher order.

The mode-locking conditions of the ultra-short pulse fiber ring laser depend on the evolution of polarization state inside the fiber loop. We observed polarization dependent output spectrum in CW state and the fluctuation of output pulse amplitude in our fiber laser experiment. PHB and PDL are two main polarization dependent effects. Environmental perturbations make the output pulse amplitude a stochastic process.

The use of nonlinear optical loop mirror with traveling wave semiconductor laser amplifier in high speed optical signal processing is reviewed. Clock signal extracted from unequal amplitude 4 X 2.5 GHz optical time division multiplexing signal and clock component generated from non-return-to-zero format data are demonstrated using a nonlinear loop mirror configuration.

A new 2 X 2 ATM photonic wavelength switching block has been presented. It is composed of wavelength beacon, wavelength filter and splitter, 2 X 2 LiNbO₂ waveguide switches and optical buffer. Different input-line cells will be converted into the cells with the different wavelengths according to their destination address by the wavelength beacon. With the wavelength routing tag, the cell could be self-routed to the destination output-line. The routing path is both low loss and los noise. ATM cell contention is settled by an optical buffer in which the fiber delay-line, LiNbO₃ waveguide switches and nonlinear semiconductor optical amplifiers are employed. Composed by various delay fibers and waveguide switches, the buffer can store 7 cells or more. This block can be easily reconfiguration and extended to the 4 X 4, 8 X 8 ATM photonic switching system. It can be used as ATM switching unit and optical cross connection component in the all optical networks. The ATM input line bit rate of our photonic switching block is 2 X 622 Mbit/s.

This paper presents a 4-channel densely spaced optical frequency division multiplexing transmission/distribution system. Good bit error rate (BER) and eye diagrams are obtained. In more than 24 hours of continuous operation, no error bit is detected (BER < 1 X 10^-14). The minimum received optical power measured before the demultiplexing Fabry-Perot filter is -30 dBm (BER equals 1 X 10^-9).

Fiber optic is the best medium for communication, FDDI, Fiber Distributed Data Interface, is the popular computer LAN over fiber optic. In this paper, we describe in details the design and implementation of our FDDI microcomputer network system named Sunrays, the stress will be lain on how the communication is realized in this network system by optic-related components.

The high density wavelength division multiplexing (HD-WDM) system presented here has 8 channels in 1.55 micrometers optical band with wavelength spacing of 100 GHz. Each channel operates at 622 Mb/s by using directly modulated DFB-LD. Accurate temperature control and current control methods have been taken to ensure the wavelength stability of 200 MHz in standard deviation. Three high-quality EDFA's are used in the 420 km optical fiber transmission to compensate the loss of fiber, star couplers and F-P optical filter. An F-P filter with 0.3 nm bandwidth and 1.2 dB insertion loss is used as a demultiplexer in front of the receiver to select every channel and reduce amplified spontaneous emission noise. An optical receiver with PIN-FET front-end has been used, which has sensitivity of -31 dBm BER equals 10^-10. Good SNR characteristic is obtained for all channels after the transmission. In this paper we describe an 8 X 622 Mb/s HD-WDM experiment system and its 420 km optical fiber transmission. Some critical problems in long distance HD-WDM transmission also have been studied in this paper.

A high density grating wavelength division multiplexer whose working wavelength is 1.536 - 1.564 micrometers for eight channels spaced 4 nm using binary optical microlenses is reported. The optimal binary optical microlenses is designed and its diffraction far field is analyzed using phase balance design method and the accumulating integral method. The coupling efficiency and the fundamental mode proportion in the receiving fiber are calculated.

A novel method of all-optical frame synchronization clock recovery is proposed for the ultra-high-speed OTDM (optical time division multiplexing) system. A wavelength different from the signal and a special time slot are used in the header of each frame to transmit the frame clock signal. At the receiver, Terahertz Optical Asymmetric Demultiplexer is used to recover the frame synchronization clock. The behaviors of 40 Gbit/s OTDM transmission systems employing this method are analyzed.

A novel all-optical clock extraction and frame synchronization recovery scheme based on SBS and NOLM is proposed. The theory is given and the wave forms of the extracted clock and frame synchronization signal are computer simulated for two cases: with two gains and with three gains. The comparison between our system and the ordinary multiple wavelength pumped Brillouin amplifier is presented. The performance and system design are discussed.

Fiber which dispersion decreases with distance in exponential power can overcome the effect induced by loss on soliton propagation. We can obtain this character by using core-radius decreasing fiber, exponentially continual decreasing or discrete decreasing (ladder fiber). Continual variation of radius will produce modes coupling. After analyses, in the continual core-radius decreasing fiber, even if v equals 2.4048, there will still be two modesc. One is stable mode when z yields (infinity) , the other is a special mode with both characters of transmission mode and of radiation mode which we called transition mode. It has the same transmission constant as the exciting mode, but its amplitude reduces at the decreasing ratio of core-radius. The effect of transition mode always exists in the exponential decreasing fiber, in spite that it can efficiently increase the distance of soliton propagation. There is no transition mode in the ladder fiber, but each section of this fiber will be shorter. In order to evaluate the transmission distance of the stable mode ground state soliton, we calculate it with the ratio of local power and threshold power, and call it threshold degree. If the ground-state soliton has the power of threshold before entering the core-radius decreasing fiber, the threshold degree of stable soliton is equal to the ratio of the order parameter of soliton N². Difference of the threshold degree between ladder fiber and exponential fiber is so little that there is almost no distinctness between them. The formula and curves of the threshold degree are given at the end of this article, which mean the preceding transmission distance in fibers.

1 Gbit/s, 50 km optical soliton transmission systems was presented. The key techniques of the system were researched. It was first presented that the fundamental and high-order optical soliton transmission was achieved using normal dispersion fiber elimination chirp in China.

In order to solve difficulty of transmission of data acquisition and monitoring signals from high voltage remote side to user side in electrical power system, some problems about a 32 Mb/s optical fiber data transmission system with time-division multiplex are studied emphatically. The optical fiber transmission system has been developed in the laboratory and has the following features: multi-input analog signals in the remote side can be merged into a single-path digital signal by using A/D conversion and multiplex techniques, this single-path digital signal is sent to user's instrument or computer device via the optical fiber transmission system with high speed. Another optical fiber transmission system with low speed is also adopted to send user's various orders to control unit of data acquisition in the remote side. Two monitoring systems of one-chip microprocessor located respectively in the remote side and user side are communicated with each other by their duplex serial ports, the system monitoring and remote controlling has been realized. One channel of duplex ports use optical fiber low speed transmission system, another channel's code has been compounded into bit stream of optical fiber high speed transmission system.

Some highlights of the development of DWDM systems and components at Siemens are presented. This includes integrated optical DWDM filters in the SiO₂/Si and InGaAsP/InP material systems realized as concave reflection gratings on the basis of Rowland and flat-field mountings and as optical phased arrays. An overview of the activities wavelength-switched optical networks with optical ADD/DROP multiplexers and cross connects is given.

We report here fabrication of highly efficient in-fiber grating bandpass filters using the established UV-side- exposure technique. Various combinations of passband/stopband and transmission/rejection of single- and multi-channel filters have been produced in hydrogenated standard telecom, high Ge-doped and B/Ge-codoped fibers. Up to > 60 dB rejection stopbands ranging from -2 nm to 55 nm, and passbands with 0.02 nm - 3 nm linewidths and transmissivity up to > 90% have been achieved with these devices. By concatenating several structures, a bandpass filter has been demonstrated with a combination of a 0.16 nm passband centered in a approximately 35 nm stopband, representing the highest reported finesse of 220 for any multi-nanometer stopband filter. We also report the first application of a grating bandpass filter for suppressing timing jitter in soliton propagation system, enabling transmission of 10 ps solitons over a distance of 2700 km.

Using grating phase vector and the phase matching condition, universal formation for fiber Bragg grating was constructed, which can be directly applied for the analysis of long- period fiber grating band rejection filters, short-period reflection filters and short-period band rejection filter (tilted grating).

The switching efficiency of nonlinear optical loop mirrors in which the wavelengths of the control pulse and signal solution straddles the dispersion zero was investigated numerically. In our analysis, the effects of control pulse parameters such as pulsewidth, central wavelength and jitter on the switching efficiency of soliton NOLM were considered. The required peak power of the control pulse to achieve maximum switching efficiency was found to decrease in as the width of the control pulse was increased. This is mainly due to the combined effect of self phase modulation and positive group velocity dispersion of the control pulse. In this paper we also show that the maximum switching efficiency of NOLMs with loop lengths of one and two soliton periods long, can be achieved with control pulse of reduced peak power if its pulsewidth is three times of that of the signal. Jitter, and wavelength detuning of the control pulse reduced the switching efficiency of the NOLM. However, more than 90% switching efficiency could still be obtained even when the control pulse central wavelength is detuned by about 4 nm or when the control pulse jitter is about 26%.

Nonlinear Kerr effect destroyed the balance of linear dispersion compensation system. Based on the different result of nonlinear Kerr effect on optical pulse with different chirp, this paper discussed unidirectional and bi- directional nonlinear adjustment system, a self regulated system was formed in the latter, it was called `chirp management method'.

A method of using a length of looped optical fiber with high cutoff wavelength as an EDFA gain equalizer has bee proposed. Such a fiber loop, with cutoff wavelength round the first EDFA gain peak (approximately 1.53 micrometers ), can act as a notch-filter by taking advantage of radiation loss, which is different from the cutoff loss of multi-mode optical fibers due to the single-mode light launching into such fiber filter, to smooth the EDFA gain spectrum.

In this paper, the method will be introduced, it's called Quantum Nondemolition measurement. The purpose is to realize a new measuring method to surpass quantum limit. It provides a new method of overcoming quantum noise. In principle, it can use any precision to detect a certain weak signal. Finally, the application of QND Measurement in optical communication will be introduced.

The concept of the squeezed state of light field as well as the theory of realizing quantum optical communication and its experimental mechanism have been given. The principles of the transmitter of the quantum optical communication and the receiver have been introduced and the keypoints of realizing quantum optical communication have been suggested.

Polarization insensitive multi-channel narrow-spacing wavelength division multiplexers (MNWDMs) based on fused and tapered single-mode optical fiber coupler are reported. The devices, operating from 1320 nm to 1520 nm, can de- /multiplex over 20 channels, with channel spacing on the order of 10 nm. The MNWDMs are fabricated from fused fiber couplers that are elongated to an isotropic point where the coupling coefficients of two polarization states are equal (C^x equals C^y). Theoretical analysis is also provided.

Fiber grating stabilized single-mode diode laser is developed in a highly reliable hermetically sealed package for dense WDM applications. It provides a very stable laser output with an output power stability of +/- 0.04 dB over 12 hours. Output wavelength accuracy of the laser is precisely controlled by a fiber grating with a fabrication tolerance of +/- 0.1 nm. The laser has a linewidth of 50 kHz, an output power larger than 6 mW and a 2.2 nm quasi- continuous tuning.

Anisotropically etched v-grooves on silicon substrate for the positioning of optical fibers have been widely implemented in fiber optics and optoelectronic applications. Because the anisotropic etching depends upon the crystallographic orientation of silicon, the v-grooves are normally formed parallel to the <110> direction. However, some applications, such as optical switches, and wavelength division multiplexing/demultiplexing devices, fan-in and fan-out configuration for fiber positioning are required. In this paper, we will report a single mode refractive plate switch where a micromachined silicon waferboard was implemented for passively positioning optical fibers. We successfully demonstrated a 2 X 2 single mode optical switch with less than 0.64 dB loss.