The pulse compression for the femtosecond photonic crystal fiber laser is obtained by hollow core photonic bandgap fibers (HC-PBGF). The fiber laser directly outputs 475 fs pulses at a central wavelength of 1040 nm with an average power of 400 mW, corresponding to a pulse energy of 8 nJ. The dispersion of the HC-PBGF is measured with a white light interferometry method, which shows that the fiber has an abnormal dispersion of about -48 ps2/km and can be applied to compensate the positive chirp of femtosecond pulses from the fiber laser. After compression from the fiber with an optimized length, the pulses are compressed to 108 fs, which is close to Fourier transmission limitation. The transmission efficiency is about 89%, which is much better than a grating pair. The spectrum keeps the same as that of the input pulse after passing through the fiber, due to the low nonlinearity and bandgap properties of the HC-PBGF.

The output of fiber optic gyroscopes (FOG) involves Gaussian white noise and fractional noise which is difficult to eliminate by traditional methods because of the non-stationary, long-term correlation, self-similarity characteristics. On account of the characteristics of the wavelet multi-resolution analysis, wavelet analysis has become a powerful tool to study fractal noises. This paper introduces an effective technique for the de-noising of FOG corrupted by non-stationary noises. The proposed method is based on a second generation wavelet transform and level-dependent threshold estimator. The whole algorithm consists of the de-composition based on lifting wavelet, parameter estimation, and level-dependent soft threshold de-noising. The de-noising method based on traditional universal thresholding wavelet is also investigated to provide a comparison with the new method. Experimental results prove that the proposed method based on level-dependent lifting wavelet outperforms the traditional wavelet de-noising method.

Based on an erbium-doped dispersion-managed fiber laser, the characteristics of noise-like pulses under different net cavity group velocity dispersions (GVDs) are experimentally investigated. Results show that the spectral bandwidth of noise-like pulse will increase as the net cavity GVD increases and attains maximum when the GVD is slightly positive. The effect of Raman scattering is enhanced due to the temporal width attains minimum. When the net cavity GVD increases continually and further into the positive region, the spectral width begins to decrease and the effect of Raman scattering is suppressed due to the positive dispersion. Our experimental results are in good agreement with the previous prediction of numerical simulation.

A novel broadband directional coupler based on an asymmetric dual-core photonic crystal fiber (PCF) is proposed. The asymmetry in the fiber is introduced by the enlargement of one air-hole in dual-core PCF. Numerical investigation demonstrate that broadband directional coupling with spectral width as large as 370 nm and polarization-dependent loss and uniformity lower than 0.2 and 0.5 dB, respectively, can be achieved. In addition, the proposed fiber shows large tolerance to the variation of the fiber parameters. In particular, the fiber length allows at least 10% derivation from the proposed fiber length of 7.7 mm.

Using the master oscillation power amplification (MOPA) technology, the dual-stages narrow linewidth fiber amplifier with all-fiber structure is experimentally studied. In the fiber amplifier, the narrow linewidth fiber laser with 20 dB spectral width of 0.078 nm is used as the seeding signal, and the side pumped coupler that is made from the fused tapered fiber, and the (6+1) ×1 multimode fiber combiner are used as the pump power coupling components, and the Yb-doped double cladding fiber with single mode core in the wavelength of 1053 nm, the large mode area Yb-doped double cladding fiber are used as the gain fibers in the two fiber stages, respectively. In the second fiber amplification stage, the back propagation light in the pump input end of the (6+1)×1 multimode fiber combiner is monitored and analyzed, which are including the spectra component and the light power. In order to suppress the spurious lasing of the amplification stimulation emission light, the length of the gain fiber is optimized experimentally. At last, the characters of the stable amplification output laser are the peak wavelength 1053 nm, total gain 27.6 dB, output power 16.09 W, and the nonlinear effects are not observed.

A new dual-wavelength erbium-doped fiber ring laser is proposed. By using multi-filtering method to select working frenquencies or modes ,the mode hopping between the neighboring modes can be effectively suppressed. Simultaneity by using the polarization hole burning effect, incorporating with the contrary propagation of the two light beams, the inhomogeneous broadening is significantly increased in the gain medium, and thus a stable dual-wavelength Er-doped fiber ring laser operating in single-longitudinal mode and single-frequency was demonstrated. Wavelength spacing between the two wavelengths was tunable from 0.019 nm to 15 nm. By suitable adjusting the tunable fiber filter, its intensity was of 25 dB over the noise and only one beat tone at 472.5 MHz was found in the spectral rang from 100 Hz to 3 GHz.

A novel two-stage cascade dual-backward pumped configuration using the synchronous pumping technique is presented to achieve a mean wavelength stable L-band superfluorescent fiber source (SFS). The effects of total fiber length, fiber length arrangement of the two-stage, and pump ratio on the output characteristics of the L-band SFS in terms of mean wavelength, linewidth, and output power are investigated. The results show that not only the output spectrum can be moved form C-band to L-band effectively but also the pump power independent mean wavelength operation can be achieved by using the two-stage cascade dual-backward pumped configuration. A SFS with linewidth of 47.3 nm, output power of 97 mW, and high mean wavelength stability is experimentally obtained with a pump ratio of 0.5 and 290 mW total pump power.

A spread equation of erbium-doped optical fiber laser was derived from the basal theory of laser. The experimental results showed that erbium-doped optical fiber exhibited gas gain when the wavelength was 1550 nm, corresponding to a low-loss communication window, possessed potential application value. It was very important parameter for the laser that influencing factor of overlap integral of the distribution of pumping fiber mode intensity and erbium doped fiber ions. Whether mode waist overlapped with the distribution of erbium-doped fiber ions was determined by various mode fields. This might contribute to an analyse of fiber mode. Influencing factors of overlap integral with medium absorption cross section were investigated. Theoretical analysis of the noise characteristics (ASE) was conducted. the analytical formula of gas gain, threshold power and slope efficiency was prescribed and a numerical model with output characteristic was developed. It were obtained by working out special computation procedure for this laser, performing theoretical arithmetic and emulation for output characteristic and discussing the effect of the configuration.

The novel cluster-solid-core photonic crystal fiber (PCF) is proposed, which is structured by the bismuth silicate glass cores with a higher refractive index and the fused silica base with a lower refractive index. In particular, the guiding is only localized in the cluster-solid-core region by the total internal reflection (TIR). While the same power output from each solid-core in the PCF can be obtained. The nonlinearity and the mode field area of the cluster-six-core PCF and the cluster-eight-core PCF versus the pump wavelength and the core diameter are discussed by numerical simulation. The results show that the novel PCF designs have the specialities of the equivalently higher nonlinearity and the effectively large mode-field area, and can offer a significant potential in high-power frequency transform.

The influence of the air hole size of different rings and the doped dielectric cylinders size in the cladding on the band gap is investigated by plane-wave expansion method(PWM), for photonic crystal fibers(PCF) based on the triangular periodic structure, the composite honeycomb structure and the improved composite honeycomb structure. It is demonstrated that photonic crystal fiber band gap is most sensitive to the air hole size variation in the first two rings. When the change of the air hole size in the m-th ring is constant, the effect of the air hole size changing on the band gap decreases with the increasing of m. Through improving the arrangement of these dielectric cylinders in structure or doping the high refractive-index medium, the band gap can be regulated or made wider effectively. Compared with other two structures, photonic crystal fiber with improved composite honeycomb structure can achieve a wider band gap.

A simple and cost-effective wavelength-switchable fiber ring laser based on a chirped moiré fiber grating (CMFG) and an erbium-doped fiber amplifier (EDFA) is proposed, and stable wavelength lasing oscillations at room temperature is experimentally demonstrated. To serve as a wavelength selective element, the CMFG possesses excellent comb-like filtering characteristics including stable wavelength interval and ultra-narrow passband, and its fabrication method is easy and flexible. The measured optical signal-to-noise ratio reaches the highest value of 50 dB and the power fluctuation of each channel output is less than 0.5 dB within an hour. The output laser power of different channels is almost identical (difference of less than 1 dB) within the tunable range. Methods to optimize the laser performance are also discussed and the superiority of the CMFG is experimentally demonstrated.

A ultra long period fiber grating (ULPFG) is a novel band-rejection fiber device with periods up to several millimeters. Some related devices have been used in measurement of multi-parameter, but it′s reported very few on how to simulate its transmission spectrum properties. On the base of coupled-mode theory and simplified three-layered model, a numerical method is proposed to simulate the transmission of the ULPFG written in single mode fiber and the linear interpolation is used to simplify the calculation. By using this algorithm, the calculation resonant wavelengths generally agree with the experimental results previously reported, which verifying the validity and reasonability of the algorithm and theory basis and effective analysis method for the witting providing ULPFG.

The diffraction characteristics of the linearly chirped phase mask is investigated using rigorous coupled-wave theory. The results show that the groove depth and duty cycle of phase mask must be controlled within the range of 242～270 nm and 0.37～0.50 respectively, in order to make the zero order diffraction efficiency less than 2% and the ±1 order diffraction efficiency more than 35%. Based on the above analysis, a linearly chirped phase mask with the center period of 1000 nm, ruled area of 100 mm×10 mm and chirp rate of 1 nm/mm has been fabricated by a new technique, which combines holographic-ion beam etching and reactive ion beam etching. The experiment and simulation both indicate that the Ar ion beam etching can modify the initial photoresist grating profile and produce a suitable duty cycle under the CHF3 reactive ion beam etching. Experimental measurements show that the zero order diffraction efficiency is less than 2%, with the ±1 order diffraction efficiency more than 35% and the maximum nonlinear coefficient of 1.6%. Theoretical analysis also indicates that the phase masks can be used to fabricate the UV written chirped fiber Bragg gratings.

Limited by the writing mode, the real refractive index distribution of the long period fiber grating (LPG) is different from that of the classic theory, which makes the spectrum of the real grating disagrees with ideal value. Fourier series is used to analyze the harmonics of Gaussian refractive index. Effect on the harmonics distribution caused by the relation between the beam size and grating constant is summarized, and the principle of optimum parameter selection is discussed. And some conclusions about LPG fabrication and character estimation are gotten. The transmission spectrum comparison between the long cyde grating written point by point with Gaussian beams and transmission by amplitude mask is obtained.

Multi-wavelength fiber ring laser based on the semiconductor optical amplifier (SOA) with sampled fiber Bragg grating (SFBG) in a Sagnac loop interferometer as the wavelength-selective filter is proposed. Four lasing wavelengths with 1.8 nm spacing have been generated stably at room temperature. The proposed laser has the advantages such as removal of the high-cost circulator, flexibility in channel-spacing tuning, and simple all-optical fiber configuration, which has potential applications in high-capacity wavelength-division-multiplexed (WDM) systems and mechanical sensors.

Quartz fiber with diameter of 93 μm is immersed into a low refractive index solution, which is mixed with ethanol and ethylene glycol doped by rhodamine 6G dye molecules. Pumped by evanescent-wave along the fiber axis, the lasing wavelength of whispering gallery mode (WGM) is found blue-shifting with the refractive index of dye solution increasing. The experimental observations are well explained by the γ(λ) curve, which is deduced from the four-energy level model of dye lasing from a WGM fiber laser and caculated by the ratio of molecular density for the upper and total lasing energy levels.

A novel fiber ring resonator based on Mach-Zehnder (M-Z) interferometer is proposed. Its transmission function is theoretically analyzed using the transfer matrix method. The expression for the full width at half maximum of the transmission spectrum is also derived. Numerical simulations show that transmission spectrum has the periodic narrow stopband filtering characteristic. The influence of phase difference between the two arms of M-Z interferometer and coupling coefficient on the transmission spectrum is also analyzed. The results are of important significance to its actual processing and improvement of filtering characteristic.

The properties of long period gratings in photonic crystal fibers (PCFLPG) are systematically analyzed by the improved full-vector effective index model and the coupled mode theory. Dual-resonance peak occurs in PCFLPG. The dependence of the coupling strength and the resonance wavelength on the hole pitch, the hole-to-pitch ratio, the grating period, the length of grating, the refractive index modulation depth and the chirp coefficient is studied. The results provide the theoretical basis for the applications of PCFLPG in the optical fiber communication, the optical fiber sensing and so on.

We introduce a new fabrication method for photonic crystal fibers (PCFs) using the hydrofluoric acid’s corrosive property. The transversal structure of a PCF can be changed by filling its air-holes with hydrofluoric acid, which corrodes the glass wall around and therefore widens the air-holes. By accurately controlling the hydrofluoric acid corrosion time, we can enlarge the air holes up to millimeter precision. This method can be used as a supplement of the traditional fusing-drawing technology to realize more complicated structures of PCFs in practice. Meanwhile, this method greatly modifies the light-guiding properties of PCFs. Experimental results indicate that, with the increase of corrosion time, the leakage loss and the scattering loss will decrease, the nonlinear coefficient will increase, the effective refractive index of fundamental mode and the equivalent refractive index of cladding will decrease, and the group velocity dispersion will be modified accordingly.

Gain flatness of erbium doped fiber amplifier (EDFA) is a critical issue for wavelength division multiplex (WDM) system, and realizing this function by photonic crystal is a new scheme proposed in this paper. We designed the gain flatness filter satisfied with special condition by analyzing the principle of gain flatness of EDFA and the different reflection character of one dimension (1-D) photonic crystal whose reflectivity is different at different wavelength. Taking the typical gain spectra of EDFA for example, we optimized the period of optical crystal conveniently and exactly using the genetic algorithm and finally designed the gain flatness filter matched with the gain spectra of EDFA. The results show that the designed cascaded 1-D optical crystal filter can flat the gain of EDFA in the range of 1530～1560 nm and the non-flatness degree is about ±0.6 dB.

In order to realize the sensing probe of micro-scale liquid and gas in fiber cavity ring-down spectroscopy system, a new method of fabricating microfluidic sensing devices is proposed. The micro-cavity on single mode 980 nm and 1550 nm fibers by direct writing is achieved with a focused near-IR 800 nm femtosecond laser beam. The width of the cavity is 4 μm, with the depth of 80 μm. The micro cavity directly written by femtosecond laser is successfully applied into fiber-loop ring-down (FLRD) spectroscopy, and its detection principle is analyzed. It is used in micro-cavity liquid absorb detection, and the relation between the detected ring-down time, the loss and the liquid concentration is deduced. With this micro-cavity, FLRD spectroscopy can realize gas and fluidic absorption measurement on micro-scale.

We describe a new method for side pumping of double-clad fiber lasers through trapezoidal micro-prism, which can pump the light sources from laser diodes, especially laser diode arrays, into double-clad fibers easily and effectively. We use a unique-designed trapezoidal micro-prism with the same refractive index as the inner cladding of double-clad fiber. The pump light can be coupled into the inner cladding of double-clad fiber via reflection of the coated side of the trapezoidal micro-prism. Advantages of this technique include no destruction of inner-cladding, high pumping efficiency, simplicity, low cost, easy industrialization and so on. The mechanism and the application method is first introduced and the theoretical coupling efficiency was given (up to 90 %). We analyze the parameters of the trapezoidal micro-prism and the light sources including line width, angle of divergence, etc.. Then we make a further discussion of its applied areas including laser diode, pigtailed laser diode, laser diode arrays, different shape of inner cladding, etc.

This article determined three kinds of raw materials: fiber-core glass、cladding glass、acid-leaching glass and designed the match of the physical and chemical performances of these materials, which directly influence the imaging quality of bundle. The quantitative relationship between the concentration, the temperature, the type and the resolution time of acid are studied to determine a series of suitable technical parameters, which are crucial to decrease the broken rate and improve imaging quality of image bundle. Through a large number of experimental studies, performance tests and theoretic analyses, many effective methods are identified to improve the optical properties of fiber image bundle, which laid a good foundation for wider application.

A passive wavelength demodulation system based on linearly polarized light interference principle is proposed. Leading-in a section of polarization-maintaining fiber to the common fiber loop mirror (FLM) is equivalent to leading-in birefringence effect to the common FLM. As the parameters of polarization-maintaining fiber are determined, the value of effectual refractive index difference is fixed and the reflective (transmission) light intensity of the FLM becomes a function of the coupler′s prismatic ratio K, the temperature t, the length of the polarization-maintaining fiber L and the included angle of the polarization directions in the two ends. When the fabric is determined, there exists a corresponding relation between the reflective (transmission) light intensity and t in the monotonic interval. The theoretical model is established according to the matrix optics principle. The impact characteristics to the relation between the reflective (transmission) light intensity of FLM and the incidence light wavelength from the length of polarization-maintaining fiber, the coupling coefficient of coupler and the incidence included angle of the polarization light are researched. Using fiber grating as the sensing head to monitor the variation of temperature, the data show that the system′s average measuring precision of the temperature can be up to 0.03 ℃ and the veracity can be up to ±0.1 ℃.

Within the framework of static scattering, scattering-induced spectral changes in the forward-scattered component of polychromatic Gaussian beams transmitting through an insulating plate with rough surface are discussed. It is shown that the spectrum may be red-shifted and blue-shifted in comparison with the source spectrum, and the spectral switch may also take place. The H-parameter (the maximum deviation of the surface profile from the mean surface line) influences spectral behavior greatly. The spectrum remains unchanged if H=0. The phenomenon of scattering-induced spectral switches of polychromatic Gaussian beams in the far zone belongs to the effect in singular optics.

The seedling of wheat (jinmai 8) was exposed to He-Ne laser (5 mW·mm-2), enhanced UV-B radiation (10.08 kJ·m-2·d-1) and the combined treatment of He-Ne laser irradiation and enhanced UV-B radiation.The research discovers, light absorbability of thylakoid membrane of wheat seedling leaves is decreased by enhanced UV-B radiation, Mg2+-ATPase and Ca2+-ATPase activity are also depressed. Activity of photophosphorylation(PSP), cyclic PSP and non-cyclic PSP, is restrained by enhanced UV-B radiation.The enhanced UV-B radiation causes damage on thylakoid membrane of wheat seedling. But certain amounts of He-Ne laser can partially repair UV-B damage on thylakoid membrane wheat seedling leaves, and reconstruct light absorbability of thylakoid membrane of wheat seedling. Mg2+-ATPase and Ca2+-ATPase activity are also raised. Cyclic PSP and non-cyclic PSP activity is increased by He-Ne laser.The SDS-PAGE result shows that different treatment groups can not induce obvious differences on the polypeptide compositions of thylakoid membrane, which will be reduced by enhanced UV-B radiation,but increased after He-Ne laser radiation.

By using two-photon excited fluorescence (TPEF) and second harmonics generation (SHG), we imaged fresh ex vivo thyroid tissues, including normal thyroid tissue,nodular thyroid tissue and papillary thyroid carcinoma tissue. As can be seen, the follicles in normal thyroid tissue are in uniform size and shape, while in nodular thyroid tissue the follicles are in different size, and there are abundant substantial cancer cells in papillary thyroid carcinoma. These results are consistent with the corresponding standard H&E histology imagings. Furthermore, the collagen distributions in normal thyroid tissue and nodular thyroid tissue are observed to be different. These results suggest that the two-photon fluorescence microscopy imaging can distinguish, the morphologic differences between normal thyroid tissue,nodular thyroid tissue and papillary thyroid carcinoma tissue in microstructure, and it has the potential to be used for minimal invasive and rapid diagnosis of thyroid cancer.

The parameter inverse algorithm of rainbow measurement was studied. The mathematic model was built and a novel inverse algorithm was presented. The new algorithm removes noise using the technique based on empirical mode decomposition（EMD）which can filter out the noise interference under low signal-to-noise ratio(SNR) condition and effectively avoid signal loss and shift. A feature point extraction technique was presented, to compress the inversion calculation. An optimal point search algorithm based on Debye theory was proposed which can rapidly find the relatively exact inversion parameter, and more accurate parameter was obtained using Mie theory. The new algorithm greatly improves the accuracy of parameter inversion, especially reduces the refractive index inversion error and expands the application scope. The algorithm was validated by numerical test in different noisy environment for water droplets with diameter range from 35 μm to 900 μm and refractive index from 1.32 to 1.34. It is showed that the inversion diameter accuracy can reach 1 μm, and refractive index can reach the third place after decimal point with the SNR above 40 dB. When the SNR drops to 5 dB, the maximum inversion error of diameter is less than 10％ and error of refractive index is less than 0.1％.

The signal-to-noise-retio (SNR) measurement is studied to achieve high dynamic range in pulse SNR measurement and meet the requirement of fast ignition of laser. The second order autocorrelation signal of short pulse occurring in nonlinear crystal is studied, which indicatesd that the pulse contrast of 2nd order autocorrelation equals that of original pulse. And the effect of the angle variation between two input beams on their output signal in non-collinear autocorrelation is discussed. A system of second order autocorrelation was built up to study the time characteristic of short laser pulse. Its dynamic range achieves ～108 in pulse contrast measurement.

Light path of an alignment system based on four-quadrant photo-detector is analyzed. The determination for input-output characteristics of the system is transformed as calculating the illumination area, and the calculation method for every quadrant is given. The mathematic model of the system is given. Simulation results show that the linearity of input-output of the system is different for different parameters of “m shape” sign. And there exists a set of parameters, with which the input-output characteristic of the system is linear. Measurement results show that both maximum align and measurement errors are less than 2 μm, which proves that the model is correct, and the alignment system can be extent to micro-displacement measurement from alignment. With this work, dull calibration work and nonlinear error can be avoided, and both efficiency and accuracy can be improved.

On the base of absorption spectra in the range of 0.2～2 THz of nine illicit drugs and three mixed drugs obtained by using terahertz time-domain spectroscopy (THz-TDS) technique, the THz absorption spectra of different illicit drugs and mixed drugs were identified by support vector machines (SVM). Absorption spectra of the nine illicit drugs and flour, which were pretreated by normalized unit, were used to train libsvm program. Absorption spectra of the illicit drugs and the mixed drugs which were measured at different time and pretreated by normalized unit too, were identified by the libsvm and the identification rate was 100%. The results indicate that it is feasible to apply SVM to identification of illicit drugs, which provides an effective method in the secure inspection and identification for illicit drugs.

An experimental system of direct-detection optical orthogonal frequency-division multiplexing (OOFDM) signal transmission over fiber was successfully built. In this experiment, the 2 Gbit/s quadrature phase shift keging (QPSK) optical OFDM signals are generated and transmitted over 200 km in single-mode fiber. After transmission in single-mode fiber over 200 km the power penalty is less than 2 dB at the bit error rate of 10-6. Comparing of waveform, electrical spectrum and constellation before and after transmission over fiber, the experimental results show that the optical OFDM signal can overcome the effect of chromatic dispersion in fiber.

The population rate and power propagation equations are presented and solved to compare the amplification performances of bismuth-based Er3+-doped fiber amplifier (EDFA) pumped by 980- and 1480-nm lasers, respectively. In both single signal and coarse wavelength-division-multiplexing (CWDM) signals inputs, the 1480-nm pumped bismuth-based EDFA provides a larger signal gain than the 980-nm pumped one does, whereas the latter provides a relatively lower noise figure (NF). Comparative results indicate that the 1480-nm pumping scheme is more advantageous for bismuth-based EDFA regarding the band width and gain property.

Surface-deposited particles can impact on the optical performance of space optical communication. A model of antenna surface contamination is set up by finite-difference time-domain(FDTD) method. Transformation from near field to far field is made, basing on the near-field light intensity distribution calculated by FDTD for emission and receiving are all from far field. It is remarkable that distribution of near-field transmitted light intensity reaches a certain value, when distance between certain radius particles reaches a value, and the distribution is regarded as a reference. The relevant maximum distance between particles is obtained, with the same particles size and different wavelength. The results show that for a certain distribution of light intensity, the longer the laser wavelength is, the greater the relevant distance between particles is on the condition that the particle size is much larger than the wavelength. While designing the defence of space optical system, the big particles forming on the optical surface should be reduced for longer carrier wavelength.

Based on the model of wireless optical communication system channel under weak atmospheric turbulence, theoretically deduction and comparatively analysis are done on modulation symbol structure, transmission power, bandwidth requirement and packet error rate of the five digital modulation schemes (OOK, PPM, DPPM, DPIM and DH-PIM). The results show that PPM need both symbol and slot synchronization, while DPIM, DPPM and DH-PIM just need slot synchronization. OOK offers the biggest average transmission power, while PPM offers the smallest transmission power, the average transmission power of DH-PIM is smaller than that of OOK, while bigger than that of DPIM and DPPM. And the transmission power characteristic of DPIM is slightly smaller than that of DPPM. When M=6, comparing to average transmission power of OOK modulation scheme, PPM can save about 15 dB, DPPM and DPIM can save 12 dB, DH-DPIM can save about 10 dB with α=2. OOK offers the smallest bandwidth requirement, while PPM offers the biggest bandwidth requirement, the bandwidth requirement of DPIM is slightly bigger than that of DPPM. And the bandwidth requirement of DH-PIM is bigger than that of OOK, while smaller than that of DPPM. When M=6, the bandwidth requirement of PPM modulation is eleven times of that of OOK, and that of DPPM and DPIM is six times of OOK, that of DH-DPIM with α=2 is three times of OOK. Under the condition of the same mean number of absorbed background photons and the same mean number of absorbed signal photons per pulse, the packet error rates increase in order of PPM, DPIM, DPPM, DH-PIM and OOK.

In the 100 Gbit/s optical signal transmission system, by comparing the transmission characteristics of the four serial phase modulation formats with those of NRZ-DPSK, RZ-DPSK, NRZ-DQPSK, and RZ-DQPSK, respectively, we show that, when each signal was transmitted over 106 km optical SMF+DCF, the NRZ-DQPSK signal has the highest chromatic dispersion tolerance when the fiber input powers of four phase modulation formats are same.If only considering first order polarization mode dispersion (PMD), RZ-DQPSK has the largest first order PMD tolerance. When adjusting the fiber input power from 0～10 dBm, RZ-DPSK format is very robust against nonlinearities. At last, each phase modulation signal was launched into a third-order Gaussian optical bandpass filter (OBPF) with different bandwidth, and their receipt performance was compared. In addition, the NRZ-DPSK signal has the best transmission performance, if it was launched into a third-order Gaussian optical bandpass filter placed with beyond 125 GHz bandwidth.

In satellite optical communication transmitter with reflective telescope of two-mirror on axis, a large mount of the transmitted energy will be obscured by the secondary mirror. A novel method based on diffractive optical elements (DOE) is proposed for offsetting it. The beam centrally obscured is reshaped to annulus beam by a diffractive beam shaper and another phase corrector, as a result central obscuration is avoided. Numerical simulation is carried out with fixed obscuraction ratio and truncation ratio, and variation of them, respectively. Subsequent numerical simulation reveals that peak energy of far field is raised about forty percent under the condition of obscuration ratio is 15, and truncation ratio is 1.5. And numerical modelling of the latter are as follows: the larger obscuraction ratio, the larger transmission efficiency of whole system and peak energy of the far field, the narrower the width of main lobe of far field pattern, and the lower relative increment of peak energy; The larger truncation ratio, the larger relative increment of peak energy of beam in far field. This work can improve the emission efficiency of transmitter and energy density of receiver plane in satellite optical communication system.

With the development of the dense wavelength division multiplexer (DWDM) technique, asymmetrical interleaver is emerged. It can be used in optical add-drop multiplexer (OADM) system and other complex networks. Michelson-Gires-Tournois interferometer (MGTI) interleaver is one of the typical schemes. It has the characteristics of compact size, low cost, simple parameters, high performance and so on. The theoretical iteration to determine the period of the MGTI interleaver is deduced from mathematical aspect, and some examples are given in detail to support it. When the reflectances of Gires-Tournois etalon (GTE) mirrors are changed, the characteristics of the intersection of the odd and even output spectrum for symmetrical and asymmetrical interleavers are different. Examples of these different characteristics are given. These conclusions will be useful for designing interleavers based on MGTI that have specified period and bandwidth characteristics. It also has instructional function for the design of special optical interference filter.

Optical wavelet decomposition was applied to the received amplitude-modulated signal transmitted through multi-span fiber links. Then the signal including nonlinear noise induced by the interaction of fiber nonlinearity and amplified spontaneous emission (ASE) noise was denoised in accordance with the theory of wavelet threshold denoise by means of optical filters. The procession mentioned above was simulated in three different fiber links and the signals after wavelet denoising and band-pass filter denoising respectively were compared in a common dispersion compensation system. The validity and feasibility of optical wavelet denoising was proved by the simulation results. It provides a novel solution to improve the quality and capacity of all-optic fiber communication systems.

A double loop optical buffer (DLOB) cascaded scheme based on collinear 3×3 coupler is proposed and the buffer principle and method of reading-out or writing-in operation of single-stage and cascade structure is analysed. Through analyzing the noise characteristics of the semiconductor optical amplifier (SOA), a conclusion is achieved that the output performance is determined by the control light power and the current injected into the SOA during writing and reading. And the possibility of multiple circulations buffering in one-stage buffer unit and buffering in the cascaded units is proposed. A cascaded experimental system consisting of two buffer units was set up. The experiment demonstrated that, when the optical packets traversing in two units of the cascaded buffer exceeded 9 circles respectively, the peak-peak value of output power did not decrease compared to the input optical signals, and signal-to-noise ratio (SNR) declined by less than 4 dB. The result of theoretical analysis and experiment both prove that cascaded optical buffer can provide a buffer from nanosecond to microsecond, which would meet the demand of optical packets switch (OPS) development in the future.

In order to solve the problem of symbol synchronization in pulse position modulation (PPM) and modulator waiting or bugger overflow resulting from the unfixed length in pulse interval modulation (DPIM) in optical wireless communications, a novel fixed length dual-amplitude pulse interval modulation(FDAPIM) is discussed. The symbol structure, transmission power, bandwidth requirement and error performance of FDAPIM in a non-dispersive channel are presented and compared with OOK, PPM, DPIM and FDPIM. Simulations show that the packet error rate of FDAPIM is higher than that of PPM and DPIM, which is similar to FDPIM and less than OOK obviously. Moreover, FDAPIM, which does not need symbol synchronization and has fixed symbol length, helps to simplify the receiver and solve the problem of modulator waiting and bugger overflow. It is superior in wireless optical communications system.

Radio over fiber (ROF) systems which employ intensity modulation with direct modulator are faced with severe chromatic dispersion-induced fading of the remotely delivered RF signals, which limits the development of millimeter-wave communications technology. Optical frequency multiplication (OFM) carry low frequency or intermediate frequency modulated signals on optical signals. The base station generates millimeter-wave signals, which effectively combatted the problem of chromatic dispersion-induced fading. This method has broad development prospects. The design of a bi-directional radio over fiber transmission system based on OFM is proposed and experimental studied. In the system, a fiber Bragg grating is used to extract light wave as a light-uplink carrier. The base station needing no light source. The loss of optical power is low, the use of resources is rational. At the base stations, low-frequency oscillator and millimeter-wave carrier are mixed to gain the uplink oscillator, which solve the problem of uplink generation. This method simplifies the system and lowers the cost.

Advanced optical modulation format is one of the key technologies of high-speed optical transmission system because of its capability in mitigating transmission impairments, such as dispersion and nonlinear effects. We study the transmission characteristics of non return-to-zero octal differential phase-amplitude-shift keying (NRZ-ODPASK), return-to-zero octal differential phase-amplitude-shift keying (RZ-ODPASK), and carrier-suppressed return-to-zero octal differential phase-amplitude-shift keying (CSRZ-ODPASK) modulation formats for 40 Gbit/s system. It is shown that RZ-ODPASK format can tolerate more chromatic dispersion than the other two formats, especially in its phase channel. Furthermore, for WDM systems, CSRZ-ODPASK format performs better than NRZ-ODPASK and RZ-ODPASK in crosstalk penalty by 0.81 dB and 0.19 dB, respectively. CSRZ-ODPASK is a good choice for high speed optical fiber communication system.

Three active phase control configurations involved in coherent beam combining of fiber lasers are introduced, and coherent beam combining of three W-level fiber amplifiers based on each phase control configuration are experimentally implemented. Comparative study and analysis on these configurations is presented based on theoretical analysis and experimental investigation. The fill factor issue involved in practical engineering is also briefly discussed.

Polarization mode dispersion (PMD) is one of the important issues which limit the high-speed long-haul communication of optical fiber. It is a challenging task to recover the distortions induced by PMD for the reason of its statistical characteristics. The concepts and mathematical description, which are important to understanding of PMD are proposed. The present development of optical and electrical techniques of mitigation and compensation for PMD are presented, as well as the latest progress for PMD treatment in the world. The configurations of the optical PMD compensator, the extraction of the feedback signals and the particle swarm optimization as an effective adaptive control algorithm are described in detail.

The principle, structure and application of fiber optical filter are introduced, and a significant conception of cascaded fiber optical filter is proposed. Its structural and working principle are observed in detail, on the base of summing up typical cascaded fiber filters. The structural design and working principle of microstructure optical fiber (MOF) and microstructure optical fiber grating (MOFG) are demonstrated, by analyzing the particular properties of them. And their application in the design of the fiber optical filters is summarized. The scheme of MOF and MOFG cascaded filter is proposed, and its future development is presented. It can broaden the category of filter scheme and make the configuration of the filter variable.

Stimulated by the ever-increasing demands of wide-bandwidth in optical communication and high-performance computing in microprocessor, silicon photonic devices are entering into the integrated and low-cost trend, and series of significant breakthrough both in theory and technology are achieved. Recent progress in the development of these photonic devices such as silicon laser, amplifier and modulator are reviewed, and their applications in optical gyroscope and optical communication are analyzed and designed. A three-dimension active resonator is designed to achieve the intergrated resonance optical gyroscope. The outlook and potential applications of these devices in future optical gyroscope and optical communication systems are presented.