Fibers with tailored mode profile may benefit special applications, for example, large mode size and low nonlinearity can improve the performance of dense wavelength-division-multiplexed systems. We demonstrate that it is possible to derive the index profile from the desired modal characteristics. The procedure may expedite the development of special fibers.

The results of investigations of reflection signals occurring at fusion splices on real cable sections of long- haul transmission lines are represented. Conditions of rising of reflection signals at fusion splices of the single mode step index optical fibers were experimentally investigated. Approximate solution to estimate probability of reflection at splice of single mode optical fibers is proposed. The results of probability calculations of reflection at splice of conventional single mode step index optical fibers are represented. Analysis of obtained data shows a good agreement between experimental and calculation results.

A synthetical equation set about optical fiber nonlinear in WDM transmission system is proposed in this paper. A supplementary Split-Step Fourier Method to solve the equation is proposed too. The equation and its numerical method can be used to analyze different fiber nonlinear effects, which will also do great help to simulating and analyzing the performance of WDM transmission system.

This paper reports on our theoretical and experimental study comparing the merits and demerits of the nonlinear effects in optical fibers for their use in high-speed and high- capacity time-division-multiplexing (TDM) and wavelength- division-multiplexing (WDM) telecommunication applications. Nonlinear effects include self-phase modulation (SPM), cross-phase modulation (CPM), stimulated Raman scattering (SRS), stimulated Brillouin scattering (SBS), four wave mixing (FWM), parametric generation, and photorefractive effects. Nonlinear effects can be useful in enhancing the fiber performances by way of fiber lasers, amplifiers, switches, logic devices, modulators, multiplexers, demultiplexers, signal format conversion devices, and wavelength conversion devices, but they can also play degenerative roles limiting the performances of optical fiber communication. The trade-off between the two aspects of the nonlinear effects, therefore, should be carefully examined to achieve a system of desired transmission capacity, performance, and function.

Short optical pulse propagation is investigated in the light guide characterized with a strong dependence of the fiber material refractive index on the radial coordinate and a weak dependence on the longitudinal coordinate, with a weak spatial bending of the light guide axis being allowed as well. A three-dimensional nonlinear wave equation used in modeling the process is solved asymptotically with respect to a small parameter setting the order of magnitude of the pulse amplitude. A relationship between the propagating modes and the eigenvalues and eigenfunctions of a singular Sturm-Liouville problem is elucidated. The pulse propagation is shown to be three-scale: the high-frequency carrier is modulated with the envelope which evolves in a two-scale manner and is described with a nonlinear Schroedinger equation with coefficients depending on the longitudinal coordinate. For several types of the transverse and longitudinal inhomogeneities, expressions through elementary functions are obtained for the transverse distribution of the wave field and the envelope soliton. The possibility is stated for managing pulse parameters by means of varying the transverse and longitudinal inhomogeneities of the light guide. A formula for amplitude modulation of the pulse due to the third-order dispersion and self-steepening is obtained and it is shown that under a certain relationship between these quantities the envelope can propagate without distortions.

A modeling approach for the simulation of fiber optic communication links is proposed. Simulation model of various signal processing operations and physical noise process is introduced. Influence of link irregularities of different types and orders on transmitted signals is shown. Results of proposed model approaching are compared with known simulation algorithms of modeling fiber optic communication systems.

The operation principle of distributed optical fiber Raman gain amplifier has been discussed. The amplification phenomena have been observed in the 1410-nm wavelength range pumped by the 1320-nm solid laser using 23-km single-mode GI optical fiber. The Raman gain is depending on optical fiber interaction length . The optical fiber effective interaction lengths are 15.5 km and 10.5 km when pump pulse peak power are 50W and 30W. The relation between the gain of Raman amplifier and pump power at different effective interaction length of optical fiber is discussed. The Raman gain of optical fiber is 0.62x10^-15 m/W during 50W pump power and the effective interaction area of optical fiber is 30 micrometers ². The effective interaction area of optical fiber is 41.4 micrometers ² during the pump power is 30W.

In this paper, we presented the results of bend loss measurements for single-mode optical fiber over wide bend radius 1mm ~ 8mm and wavelength 1530nm ~ 1565nm. The oscillations caused by the coupling between the whispering gallery mode propagating in the cladding and the buffer and the core guided fundamental mode was observed versus both bend radius and wavelength. And a good agreement between the experimental results and the theoretical numerical evaluation was obtained.

This paper reviews recent developments in silicon photonic technology, and its advantages and challenges in optical networking applications. The paper also addresses the multiple optical functions that silicon technology can presently address, as well as photonic integration on silicon.

Planar Lightwave Circuit (PLC) technology has been considered as a promising route to integrate a greater number of channels and more optical functionalities onto a small foot print, enabling smaller device sizes and lower costs of manufacturing by using existing semiconductor process technologies. Among several planar technology platforms, silica-on-silicon technology comprised of a silica higher index core and lower index clad has taken the lead in this direction. One of the major advantages of silica based PLC technology is its relative ease to couple to a single mode silica fiber because of a close match of the index and dimensions of the waveguide core of planar chip and fiber. In this structure, to completely confine and guide light signals, the silica layer stack, including lower clad, core and top clad can be as thick as 20 - 40 microns, in which the core layer thickness is around 6 - 8 micron. This has presented a major challenge to several major silica film deposition technologies including CVD, FHD, PVD, and Sol-Gel processes. In addition to basic requirements for optical quality of the glass film, low cost manufacture also demands a high deposition rate to reduce process costs in the fabrication of these planar chips. In this paper, we present a high throughput and planar glass coating technology to lay down doped and undoped glass films at unprecedented rates. The technology is comprised of a laser reactive deposition (LRDTM) process developed based on our nanoscale particle manufacture (NPMTM) methods pioneered by NanoGram Corporation. We report results on planar glass films deposited using this technology and describe the concepts employed using this technology in manufacturing. Furthermore, we will compare it with various existing glass film deposition technologies.

The organic-inorganic waveguide fabrication procedure is studied with sol-gel technology. Channel waveguide and 1x4 power splitter were fabricated. The propagation loss is about 0.5dB/cm for channel waveguide. Silicon V-groove was fabricated and it is easy to position fiber to simplify the process for coupling between fiber and waveguide. The fiber was glued to the input side of waveguide. The insertion loss is about 9dB.

Polymeric optical waveguides are fabricated by using optical polymer benzocyclobutene BCB). The properties of BCB include good thermal stability and high optical transmission. Anisotropic etching of BCB has been characterized by reactive ion etching. The output mode distribution has been examined by CCD measurement system. Also, an optical coupler based on multimode interference (MMI) effect has been designed and fabricated. We show that such MMI couplers can offer superior properties such as low excess loss and good tolerance to the variation of wavelength. The measurement results are presented.

Organic-inorganic hybrid materials with superior optical properties were prepared using the sol-gel process. Planar waveguide based on the sol-gel hybrid materials was also characterized. A conventionally used intermediate for synthesizing organic-inorganic hybrid materials is organically modified metal oxide nanoparticles. Metal oxides containing functional groups were prepared by reacting organic silane and metal alkoxide. Experimental results indicate that thin films with a wide range of optical properties can be prepared by varying the composition and molecular structure of the intermediates. Additionally, the typical reflective index of sol-gel thin film ranges from 1.45 to approximately 1.65. A cladding layer and a core layer can therefore be easily prepared by controlling the content of nanoparticles. Also investigated herein was how composition and process conditions affect optical and surface properties of planar waveguide.

A radial finite-difference beam propagation method is proposed systematically with circular cylindrical coordinates, which is more accurate for simulation of some radiated waveguide structures. Theoretical design and simulation of low insertion loss arrayed waveguide gratings with couplers of tapered arrayed waveguides are presented using this full-vectorial beam propagation method.

The grating period of optimal all-optical converter based on periodically poled LiNbO3 (PPLN) waveguide dependent on the mode sizes and effective index have been theoretically investigated. Variational method of TM mode in an annealed, proton-exchanged waveguide is first discussed. The optimal grating periods are obtained, which are sensitive to the waveguide width and wavelength change of pump waves, and not to input signal waves. The grating periods in 1.5 um-band are consistent with previously published experimental results.

A dielectric waveguide structure analysis problem pursing more broad purposes comparing to known spectral problems for eigenfields determination in the guided slow wave classes and respective lengthwise wavenumbers is proposed. In this case the problem is considered both as particular problem, solved in the limits of common problem analysis of composite system, including step-by-step conjunctions (both directly and by conjugating transfers) of dielectric waveguides with different forms and of cross-sections, and refractive index profile. Specific problem character is necessity of solution determination in significantly more broad class including all guided slow waves, emission modes and free oscillations. Such broad solutions set is necessary for following 'sewing' in splice cross-section of preassigned waveguide field and field of another waveguide or conjunction transfer.

Beam out of SMF can be treated approximately as Gaussian beam, and the N.A. of SMF is able to be calculated based on the approximation. By ABCD matrix and q parameter its propagation in the Grin lens is analyzed. The couple loss between Gaussian beam and fiber is analyzed by overlapping integral. The approaches to minimize the couple loss through the optimization of design are described. The principle and approach to tune the filter center wavelength by the incident angle of beam are given with tuning formula.

Flexural waves on fiber and fiber Bragg gratings generated with applied ultrasounds and loading were used for switching the reflection wavelength of fiber Bragg grating and for controlling the transmission spectra of fiber. By producing lateral vibration of a fiber Bragg grating, which has been etched in cladding, it was found that the reflection wavelength could be switched from the Bragg wavelength to other wavelengths, which corresponded to the conditions of strong coupling between core mode and cladding modes. By adjusting the applied voltage for acoustic waves, the relative strength of different reflection wavelengths could be well adjusted. Theoretical analysis of phase-matching condition indicated that the diameter of etched cladding played a key role in controlling the switched reflection wavelength. Flexural waves were also generated on fiber by applying loading with one or two periodically corrugated plates. By adjusting the orientation of the periodical corrugation, loading level, and the relative position of the two corrugated plates, depressions of transmission spectrum at various wavelengths could be well controlled. The spectral depressions were caused by the coupling between core mode and various cladding modes. Such depressions were used for gain equalization of erbium-doped fiber amplifiers. The equalization operation was more efficient with curved fiber under loading. Control of fiber curvature for various forms of spectral depression will be discussed.

In this paper we introduce the characteristic of the long period grating and methods to fabricate LPGs which are used as gain equalization filter to get broadband amplifiers. Long period fiber gratings used to flatten the gain spectrum of erbium-doped fiber amplifiers (EDFA) were fabricated in experiment. The bandwidth of the EDFA is 35 nm with the gain variation no more than +/- 0.5dB.

An effective method for photosensitizing fiber is presented in this paper. By adopting this method, the standard single- mode communication fibers are exposed to the flowing hydrogen gas at high temperature. We cannot only write the fiber gratings with different reflectivity, but also load hydrogen at different local position of fiber, which is very convenient for us to write the fiber gratings while the fiber is in fiber-based devices.

In this article, we used weakly guiding scalar approximation and coupled-mode theory to model long-period fiber gratings precisely. We also analyzed some phenomena about the growth and annealing of the LPG in H₂-loaded fiber using molecular diffusion theory. At last, we developed a novel method to fabricate long-period fiber gratings with demanded transmission spectra and achieved a gain-flattened EDFA with a gain variation of +/- 0.5 nm in 35-nm bandwidth.

A sampled Bragg grating (SBG) with a chirp in sampling period (CSP) is fabricated. When stress gradient is applied in the SBG with CSP, the characteristics of the spectrum response are different from that of a SBG without CSP. These experimental phenomena are consistent of the previous predictions. The stress-gradient SBG with CSP may be used as a tunable compensator for both dispersion and dispersion slope.

Novel optical fiber torsion sensor based on LPG pair was proposed and the effect of the twist angle on the torsion was characterized. The transmission of the fringes at peak wavelengths was changed by the twist of the optical fiber with the LPG pair and it is attributed to the polarization dependence upon the twisting of the fiber. The variation of the transmission depends on the input polarization state, which is affected by the applied torsion.

The paper presents a novel microwave transversal filter based on spectral tapping of broadband light using fiber Bragg grating array. This structure has the advantages that it can achieve arbitrary tap weighting by controlling the reflectivity of the grating array in the fabrication, is readily scalable to a large number of taps without insertion loss increasing, and is tunable by adjusting the center wavelengths of the gratings to adjust the basic time delay provided by a dispersive element. Experimental results demonstrate our conclusions in the paper.

A study of cladding mode loss behaviors of fiber Bragg gratings (FBG) by applying stresses is described in this paper. Under an axial compressive stress the amplitude of cladding mode losses decreased from 1.44 dB to 0.88 dB with a peak wavelength shift of 0.04 nm to shorter wavelength, while under an axial tensile stress they kept unchanged. The variation of cladding mode loss of FBG under different curvatures of bending was also studied. It was observed that the extent to which the cladding mode loss changes was related to bending directions, which indicates a non-uniform index perturbation distribution. The experimental results were explained by analyzing the mode coupling.

A simple method of fabricating long-period fiber gratings, by performing an electric discharge to optical fiber, is presented. Standard single mode fiber is used without hydrogen loading. Grating filters present competitive characteristics, very low insertion loss and high dynamic rejections. We have performed high temperature characterizations of realized gratings in the range 30 - 1200 degree(s)C. Resonance wavelength shifts behavior and grating stability at several annealing cycles have been investigated. The temperature sensitivity are in good agreement with recent published works. Irreversible evolution of the peak shifts is to be emphasized.

A novel method to detect the small wavelength shift of the fiber Bragg grating used in an electric current sensor with a comb-like fiber filter is proposed in this paper. The wavelength filter was constructed by joining a piece of hi-bi fiber in the loop of a normal fiber Sagnac interferometer, which may result to a periodically varied spectrum in the reflection or transmission light. Therefore the small wavelength shift of the fiber grating caused by the change of the applied magnetic field can be detected by monitoring the intensity of the light traveling through the comb-like filter. With a 0.8-nm spacing filter used in the measurement, a sensitivity better than 0.01 nm for the Bragg wavelength shift of the fiber grating (limited by the noise of the electronic circuit and detection instruments) was obtained in the experiment. The proposed demodulation scheme provides a new approach to the detection of small wavelength shift of fiber grating.

A novel dispersion slope compensation by applying a strain gradient on a grating has been proposed. The strain gradient can produce both chirp in the grating period and chirp in the sampling period, which can be used to compensate for fiber dispersion and dispersion slope simultaneously in WDM system.

In this article, we introduce the fabrication of apodized chirp FBG by scanning method, which monitored by computer. The FBGs are 13.5 cm long with 3 dB bandwidth 0.851 nm and 0.423 nm, respectively. The reflectivity are flatness with ripple coefficient less than 0.7 dB and the ripple coefficient of time delay are less than 20 ps. The dispersion of 10 Gb/s 100 km and 200 km G.652 optical fiber is compensated by the grating respectively, and more than 98% dispersion is compensated. (The original pulse width is 36.78 ps; after compensation the pulse width is 37.23 ps and 37.19 ps). With 10^-10 BER, the power penalty of the system is 0 dB.

Chirped fiber Bragg grating (FBG) is one of most attractive components for chromatic dispersion compensation. In this paper, we discuss the possible factors that affect the characteristics of chirped fiber grating made by phase mask technique, including collimating of writing laser beam, growing rate and using non-zeroth-order suppression diffraction phase-mask. Meanwhile, the experimental results show that a 10cm-long chirped fiber grating fabricated through this processing was reasonably feasible for chromatic dispersion compensation in 10 Gbit/s transmission system.

Polarization mode dispersion (PMD) has become the major limiting factor for long haul high bitrate optical fiber transmission. This paper analyzes measurement methods of PMD in optical fiber with the polarization dependent loss (PDL) and the effects of the PDL and wavelength-scanning interval on the measurement results. Finally, we perform Monte-Carlo simulations with waveplate models on the statistics of first and second order PMD in single mode fiber with the PDL.

Polarization mode dispersion (PMD) is a serious limiting factor for high bit rate optical telecommunication systems. It is important and necessary for network managers to obtain PMD information at single end of the fiber cable. In this paper, a novel measurement method of PMD in optical fibers and devices is proposed, which is based on coherent optical frequency domain reflectometry technique (OFDR). In the method, a frequency-shifted feedback (FSF) fiber laser is developed as light source; therefore a frequency chirped probe light with good linearity, wide chirp range, and high chirp rate is realized. The PMD is determined by self-delayed heterodyne detection from the beat frequency generated by interference between lights from the Fresnel reflection at the far end of the device under test, which makes the measurement at single end of the device possible. Experiment is demonstrated on both polarization maintaining fibers (PMF) and single mode fibers (SMF), and results are in agreement with interferometric method.

Polarization mode dispersion is measured by using Sagnac Interferometer and Polarization Multiplexed Solitons and is compensated successfully by using polarization controllers and PMF for the first time in China. The principle and results of the experiment are analyzed.

Eight-wavelength Er-doped fiber lasers with lasing wavelength separations approximately 1.6 nm and approximately 0.8 nm, respectively, have been achieved by using a Cascaded fiber Bragg grating (CFBG) in the fiber lasers and cooling the Er-doped fiber with liquid nitrogen. Our experiment shows that, utilizing the CFBG to select the lasing wavelengths, it is convenient to achieve fiber lasers with lasing wavelengths and lasing wavelength separations matching the ITU (International Telecommunication Union) channel allocation grid well.

The high power fiber laser is one of the hot topics in the laser science and technology recent years. It shows good application prospects in the field of communication, printing, medicine, sensing and so on. Double-cladding rare- earth-doped fiber lasers are currently a preferred choice for high power performance. This paper reports the theoretical and experimental research of Yb-doped double- cladding fiber laser pumped by a 915-nm broad-stripe laser diode. An F-P cavity configuration was adopted by using an output mirror with 95% reflectivity at 1020 nm to approximately 1100 nm, and a dichromatic mirror for pump coupling. A slope efficiency of 51%, and a total optical-to- optical conversion efficiency of 24% were obtained experimentally.

Using the characteristics of precise wavelength-selected and special tuning method of fiber grating, stable pulses train with a wavelength-tunable range of 8 nm at a repetition rate of 2.5 GHZ has been achieved in an actively mode-locked erbium-doped fiber ring laser.

In this paper a new structure all fiber Q-switched Erbium-doped fiber laser by using all-fiber wavelength selective intensity modulator based on fiber grating loop mirror (FGLM) was reported. This Q-switched scheme not only modulates loss of the cavity but also selects wavelength. Stable optical pulse with 3 dB linewidth of 0.07 nm, pulse width of 1.4 microsecond(s) , average power of 14.2 mW, and peak power of 1.267 W at 80 mW pump power and 8 KHz repetition rates was obtained in experiments. The generation of single laser pulses and its stability were discussed.

It is demonstrated that strong Bragg and long-period gratings can be written using the frequency tripled output from a high repetition rate Q-switched Nd:YAG laser. The refractive index modulation induced by the pulsed near-UV light is estimated to be about 4.5x10^-4, estimated both based on the periodic transmission property of long- period gratings and the reflectance of uniform Bragg gratings. Although a peak pulse intensity of the near-UV light as high as 2x10⁷ W/cm² has been used, no loss due to laser induced damage to the core was observed.

Dispersion properties of the novel tapered air-silica microstructure fibers are measured between 1.3 and 1.65 micrometers by white-light interferometry. Dispersion values ((beta) ₂) of -181 ps²/km and -152 ps²/km were obtained for 2.2 micrometers and 3 micrometers core sizes, respectively, at (lambda) equals1.55 micrometers .

The crosstalk performance of a four-port electrooptic tunable filter in lithium niobate is analyzed, based on the transient response of the filter to an input optical pulse. Crosstalk is calculated for Blackman apodizing functions for input pulse widths representative of high-data-rate systems. It is concluded that crosstalk level below -30 dB for 20 Gb/s data rates and 100 GHz channel spacing is achievable with presently available substrate dimensions.

In this paper, a new physical model is proposed. For a uniform Bragg grating, the index modulation distribution is a cosine profile. We slice the grating into many slabs and each slab can be looked as a thin surface. A slab has higher or lower index modulation than its adjacent slabs. A slab with high index modulation and its adjacent slab with different index modulation can be taken as a Fabry-Perot cavity. Thus a grating can be looked as a system that consists of a series of a coupled Fabry-Perot cavities. A matrix method is introduced, which relies on the calculation of the reflected and transmitted fields at an interface between two slabs of dissimilar refractive indexes. The simulation results can explain the properties of fiber grating well and show good consistency with previous conclusion.

This paper demonstrates a novel dual-period fiber grating sensor which can measure strain and temperature simultaneously. The dual-period fiber grating consists of a long-period fiber grating (LPG) and a fiber Bragg grating (FBG) which are written in the same section of an uncovered hydrogen-loaded fiber orderly. As is known, the Bragg wavelength of LPG and that of FBG have the different sensitivity of strain and temperature, then strain and temperature can be determined simultaneously by measuring the two transmitted Bragg wavelengths of the dual-period fiber grating. The accuracy of the sensor in measuring strain and temperature is estimated to be +/- 16 (mu) (epsilon) in a range from 0 to 1700 (mu) (epsilon) and +/- 0.8 degree(s)C from 20 to 120 degree(s)C, respectively.

Using the sensitive characteristic of fiber grating, the standard characteristic of the equal-intensity beam has been measured in our experiments. The data are compared with their theoretical values. The results indicate that the measurement of fiber grating is effective and exact for monitoring standard beam. The theoretical value and the experimental value coincided very well. An applied method to measure Young's modulus of material is proposed.

A transfer matrix of an arbitrary period in a long-period fiber grating (LPFG) is derived. Cascade of such matrices can be used easily to calculate the overall performance of LPFG with fast variation in parameters (which is common practice in LPFGs) such as period length, strength, etc. more precisely. Results show that the difference in transmittivity between our work and traditional coupled-mode theory becomes obvious when abrupt change such as (pi) phase-shift occurs. This method can be used in the mask design aiming at overall performance optimization through period-by-period pattern adjustment. Finally, a genetic algorithm is used to optimize the LPFG period by period.

It is very important to get optical fiber Bragg grating (FBG) with stabilize property, this article briefly describes the anneal characteristics of H₂-loaded FBG, the experiments show that after annealing the wavelength ((lambda) ), 3 dB bandwidth ((Delta) (lambda) ) and reflectivity (R) of the FBG all changed, these changes are relative to many parameters, such as the lay time of the H₂-loaded optical fiber, the lay time of the FBG, the channel numbers of the FBG, the reflectivity of the FBG, and the bandwidth of the FBG and so on.

Refractive index change in the core of optical fibers by CO2 laser irradiation was measured by using a long period fiber grating (LPG) pair. Effect of drawing force applied to the optical fibers during drawing process on the refractive index change upon the CO2 laser irradiation was investigated. The refractive index was found to decrease linearly with the drawing force and it was due to the relaxation of the residual stress. Effect of the CO2 laser output power on the residual stress relaxation and the fiber elongation was also studied.

Er:LiNbO₃ and Mg:Er:LiNbO₃ crystals were grown by the Czochralski method. All of crystals were possessed with polarization. In order to investigate the mechanism of OH absorption peak shift, the infrared absorption spectra of the crystals were measured. The absorption edge of ultraviolet-visible absorption spectrum of Mg:Er:LiNbO₃ crystal showed a shift towards shorter wavelength. The fluorescence spectra of the crystals were investigated. The laser vibrate of Mg:Er:LiNbO₃ crystal was realized easily at 1.54 micrometers , 0.887 micrometers and 0.5 micrometers . Benzoic acid was used as proton transfer reagent to make the waveguide substrate. By using the holograph method, the photodamage resistance ability and the enhance mechanism of the Mg:Er:LiNbO₃ crystal waveguide substrate was measured.

Internal field correction elements of the waveguide laser resonator on the basis of statistically homogeneous and periodic structures which can be used for enhancement of operation of CO₂ waveguide laser is studied. A diffraction model that can incorporate the effect of light scattering by waveguide wall for typical experimental conditions is formulated. Resonator is divided into a number of longitudinal segments to obtain required precision. Optical losses for eigenmodes of such system (eigenvalues of the round-trip propagation operator) have been investigated for different parameters of the waveguide resonator. A direct comparison between theoretical losses behavior and experimentally measured ones demonstrated a satisfactory agreement for various conditions.

For integrated-optic waveguides, propagation loss and mode- profile are important parameters. In this work, a camera has been utilized to measure the propagation loss for planar waveguides and mode profile for channel waveguides. Measurements have been carried out on ion-exchange waveguides, at 633 nm and 1310 nm. The measured mode profiles have been used to calculate coupling loss between an optical fiber and channel waveguides. It is proposed that mode profile measurements may also be used for determining propagation loss of channel waveguides.

In this research, Czochralski method was used to grow Zn:In:LiNbO₃ crystal. The lattice constants, ultra- visible absorption spectra, infrared absorption spectra and photodamage resistance ability of the crystal were measured. The photodamage threshold of LiNbO₃ and Zn:In:LiNbO₃ crystal waveguide substrate were investigated by the m-line method. It is found that the higher the concentrations of In and Zn were doped, the more the absorption band of crystal was shifted to short wave. The OH absorption peak of Zn(3mo1%):In(2mo1%):LiNbO₃ and Zn(3mo1%):In(1mo1%):LiNbO₃ crystal was located at about 3484 cm^-1, and that of Zn(3mo1%):In(3mo1%):LiNbO₃ crystal was located at about 3515 cm^-1. The photodamage resistance ability of Zn(3mo1%):In(2mo1%):LiNbO₃ crystal was two orders of magnitude higher than that of LiNbO₃ crystal. The photodamage threshold of LiNbO₃ crystal waveguide substrate and Zn:In:LiNbO₃ crystal waveguide substrate were 5x10³J/cm² and 1x10⁶J/cm², respectively.

It is not generally known that light in the visible region can produce a time-dependent damage of optical fibers. For application in a novel laser projection system, fibers with silica core and fluorine doped cladding were fabricated by MCVD technique. The transmission behavior in the visible and ultraviolet spectral region was investigated. Modifications of the preparation process comprised the deposition and collapsing under reducing or oxidizing conditions to influence oxygen deficiencies and chlorine content, the treatment with water vapor and hydrogen, and the deposition of the core with small amounts of dopants as germanium. The complex diffusion and reaction behavior of hydrogen was studied and described by temperature- and concentration- dependent diffusion coefficients. All these modifications correlate with specific variations of the loss spectrum and with the fiber lifetime under blue light illumination at 446 nm wavelength with a mean power of 1 Watt corresponding to an intensity of about 0.6 MW/cm². In the result, an increase of the power stability of the fiber and a prolongation of the lifetime by a factor of about 20 could be achieved by carefully tailored preform treatments.

Approximate solution for splice of dispersion shifted optical fibers is introduced. The Gaussian approximation to determine fiber waveguide parameters of spliced fibers with arbitrary index profile is used. Mode power redistribution at splice of optical waveguides is described by applying of mode coupling theory. The results of calculations of mode coupling parameters at splice of conventional dispersion shifted fibers are represented.

Methods of evaluation of optical fibers splice irregularities are described. The data of investigations on existing cable sections of long-haul fiber optic transmission line are represented. Statistical data processing results including statistical distributions of spectral and correlation functions are proposed. Model based on obtained data analysis was developed to simulate optical signal propagation along piecewise-regular transmission line. Results of estimation of spectral characteristics of reflection coefficients of piecewise regular transmission line were obtained. It is shown a stimulation of coherent components of responses is possible under increasing of irregularities number in the non-ordered piecewise-regular transmission lines.

Stimulated Brillouin Scattering, observed in an optical transmission system using fibre lasers as signal sources, was suppressed by external phase modulation. The threshold power of SBS in a single mode fibre with 8.3-micrometers diameter was as low as 2 dBm due to a narrow spectral linewidth of a fibre laser. At 20 MHz phase-modulation, modulation voltages above 5.3V suppressed the first order Stokes more than 25 dB. RF spectrums of the fibre laser phase-modulated at or above 5.3V showed multiple sets of sideband components higher than the carrier frequency component in amplitude. The minimum spectral bandwidth of a fibre laser with 20 kHz bandwidth was broadened to 120 MHz at this modulation condition. The results signified broadening of the effective spectral linewidth of the fibre laser by phase modulation.

Following coupled mode approach, we report ab initio calculations of the signal intensity obtainable at the output end of a fiber optic coupler in a standard OCT technique and the results have been verified experimentally. The calculated intensity output varies periodically with respect to the path length difference between the sample and the reference arm and represent the interference signal, which sustains within the coherence length of the source. In the experimental setup, we have used 670-nm semiconductor diode laser possessing coherence length of 60 micron as a source. We have used a sample consisting of thin layer of glass plate and mirror. Reference mirror of 80% reflectivity was chosen. The output from the coupler was read on the Digital Storage Oscilloscope. A comparison of the theoretical plot of signal amplitude as a function of reference mirror position with the trace of the signal obtained on DSO exhibits good matching. The refractive index of the glass plate as calculated experimentally was 1.50 +/- .0125 which agrees well with the standard value. The experimental setup can enable one to determine the refractive index as well as optical thickness of any thin film simultaneously. The signal-to-noise ratio was found to be approximately 20 dB.