At present, the mature laser driver chips are all digital driver chops for digital optical output, which cannot meet the driving requirements of broadband analog laser in satellite communication, radar, and other fields. In this paper, the butterfly packaging distributed feedback laser module is used. Through the improvement of automatic power control(APC) circuit, automatic temperature control(ATC) circuit and working parameter detection circuit, a drive circuit suitable for analog laser is designed. The average amplitude response gain of the drive circuit is 2 dB, the roughness is 0.6 dB, and the maximum input voltage standing wave ratio and output input voltage standing wave ratio are 1.37 and 1.3 respectively.

Due to the influence of target motion on the post-processing phase noise compensation method, the phase noise of the echo beat signal does not match the phase noise obtained by the auxiliary interferometer, resulting in the introduction of additional residual phase noise. In order to solve this problem, the influence of target motion in frequency modulated continuous wave (FMCW) lidar system on the traditional light source phase noise compensation method is analyzed, and a new method of light source phase noise compensation by estimating target distance and velocity is proposed. The light source of the system is a distributed feedback(DFB) laser, which uses direct current modulation for linear sweep. The experimental results of moving objects show that the measurement accuracy is increased by 41 times by using the new light source phase noise compensation method, and the distance and speed can be accurately measured at the same time.

Aiming at the influence of low-pass filter in optical fiber nonlinear compensation on the algorithm complexity and compensation accuracy of digital back propagation(DBP), the nonlinear compensation characteristics of 256 Gb/s polarization multiplexing 16 order quadrature amplitude modulation(PDM-16QAM) signal with Bessel, Gaussian and Butterworth low-pass filters are studied. The experimental results show that when the step size is small, the influence of three low-pass filters on DBP algorithm is basically the same, when the step size is large, the performance of high-order Bessel low-pass filter is the best. In addition, when the order of the low-pass filter is 1 and the 3 dB bandwidth is fixed at 8 GHz and the step size is greater than 40 km, the Q factor of the Gaussian low-pass filter is about 0.1 dB better than that of the other two low-pass filters.

In order to ensure the reliability and stability of optical fiber communication system, an in-band optical signal-to-noise ratio(OSNR) monitoring technique is proposed, which is independent of modulation format and insensitive to dispersion and polarization. By adjusting the center wavelength of the broadband tunable optical bandpass filter, the optical power of the channel on the link is sampled, and the measured optical power is used as the input feature of the machine learning algorithm Gaussian process regression(GPR) to accurately estimate and monitor the OSNR of the channel on the link. The experimental results show that in the OSNR range of 2-30 dB, the technology can achieve accurate OSNR monitoring, and is robust to chromatic dispersion(CD), polarization mode dispersion(PMD) and cascaded filtering effect (CFE), which is independent of modulation format and rate.

Optical fiber leakage monitoring technology is internationally recognized as a promising solution for long-distance pipeline leakage monitoring. However, there is no clear effective monitoring scope for buried gas pipeline. In order to determine the effective monitoring range, the leakage simulation tests with different positions and different apertures are carried out on a 355 mm diameter pipeline with different nitrogen pressures. The test results show that the effective range of the fiber-optic temperature sensor is little affected by the size of the leakage aperture, but is greatly affected by the pressure and position, and is also affected by the soil compactness. In practical engineering application, the layout scheme of optical fiber temperature sensor can be adjusted according to the above factors to improve its monitoring effect.

In engineering practice, the optical fiber sensor with multi-parameter simultaneous measurement function has great market demand. For multi-parameter simultaneous measurement, a long-period fiber grating(LPFG) and a tapered fiber are cascaded to form a sensor. The sensing characteristics of the sensor for ambient temperature and axial strain are studied. Using the temperature and strain sensitivity of the two resonant peak wave-valley in the sensor transmission spectrum, the measurement matrix is constructed to eliminate cross sensitivity and complete the simultaneous measurement of temperature and axial strain. The experimental results show that the center wavelength of the resonant peak wave-valley of the sensor has a good linear relationship with temperature and axial strain. The maximum temperature sensitivity is 40.12 pm/℃ and the maximum strain sensitivity is -1.502 pm/με.

In order to improve the sensitivity of optical fiber partial discharge detection, a design scheme of optical fiber Fabry Perot(F-P) sensor with beam supported membrane structure for partial discharge detection is proposed. The response frequency, sensitivity, linear range and flatness of the sensor are simulated and analyzed under different geometric parameters. The simulation results show that, compared with the optical fiber F-P sensor with circular membrane structure, the optical fiber F-P sensor with beam supported membrane structure not only shows higher sensitivity(nearly three times higher sensitivity in some cases) and wider frequency working range, but also improves the linear range and flatness of the sensor.

Aiming at the requirement of efficient excitation of whispering gallery mode(WGM) in optical microcavity, and based on the calculation results of mode electric field distribution by finite element software COMSOL, a simulation method for the excitation efficiency of WGM is designed. The method can be used to simulate the maximum depth of resonant peak of different modes under different coupling conditions of microcavity and tapered fiber, so as to determine the coupling condition of efficient excitation of the mode. On this basis, the excitation efficiency control of the mode and the excitation of high-order azimuth modes are simulated and analyzed. The simulation results show that by selecting a tapered fiber with a matching size and finely adjusting the coupling distance, the excitation control of the fundamental mode of the fabricated microrod cavity from under-coupling to over-coupling can be achieved. By adjusting the coupling position, the high-order azimuth modes can be excited with high efficiency.

In view of the problems of complex structure, excessive loss and low speed in the fiber optic rotary joint(FORJ), a high-speed single-mode FORJ structure is proposed, and its performance is tested. The loss of optical signal transmission in FORJ is analyzed and studied. The experimental results show that the designed single-channel single-mode FORJ can transmit optical signal at high speed of 8000 r/min, the loss is 19.6 dB, the maximum impact load is 20 m/s2, and the maximum radial amplitude of the rotating input shaft is 0.63 mm, which can adapt to the harsh working environment.

The traditional WDM network uses fixed grid, which can not meet the network requirements. An improved graph coloring based routing spectrum allocation(GT-RSA) algorithm is proposed. Firstly, the first k shortest path algorithm is used to determine the candidate route set, and the candidate route graph is established according to each candidate route set. Then, the mixed integer linear programming model of graph coloring theory is used to select the route, and the optimal solution is obtained according to the maximum saturation priority algorithm of branch boundary. At the same time, the coloring partition allocation of spectrum is completed. Finally, partition first-last-fit(PAR-FLF) algorithm is used to allocate spectrum resources. The simulation results show that GT-RSA algorithm has lower spectrum resource consumption, lower blocking rate and higher average link continuity rate.

In the complex practical application of optical fiber sensing system, it is necessary to accurately identify and locate the adjacent multiple disturbance points on the same optical fiber. Based on the background of external disturbance identification of sensing technology, combined with the structure of optical fiber sensing system, the typical curves of vibration and non vibration regions of optical fiber sensing signal are obtained, and the error cumulative value algorithm of single peak signal is proposed. On the basis of the characteristics of multi peak signal, the separation algorithm of multi peak signal is obtained by combining Gauss equation and Lorentz equation. The experimental results show that the algorithm of error cumulative value of single peak signal can simultaneously recognize the accuracy of interference location and the real-time performance of the system, and the separation algorithm of multi peak signal can separate two independent interference signals and extract the equation. This scheme can effectively improve the recognition accuracy when the signal peaks overlap more or other signals interfere.

The Ko displacement theory can reconstruct the structure accurately. In order to apply this theory to the practical engineering, the optical frequency-domain reflection(OFDR) distributed fiber sensor is used as the measuring tool, and an experimental scheme of deformation estimation based on equal strength beam is designed. The experiment is divided into six stages of loading on the beam of equal strength, and the true deflection values of four measuring points under each stage load are measured by dial gauge. The deformation reconstruction of deflection is carried out according to the strain value measured at each stage. Finally, the deflection values obtained by the two methods are compared. The experimental results show that the strain coefficient of the fiber is 0.71666, the maximum error between the deflection value of deformation reconstruction and the true deflection is 0.586 mm, which is in line with the experimental expectation.

Polar regional communication has always been a difficulty in the field of satellite communication. In order to meet the needs of polar regional communication, a polar laser communication system based on polar orbit laser communication satellite and geosynchronous orbit laser relay satellite is designed. This paper analyzes the calculation and analysis model of satellite communication window, describes the application and application scenarios of the system communication link, simulates the polar communication window, and gives the window distribution list. The results show that the average daily communication window can reach 3.4-3.96 h.

Software defined network(SDN) controller system is the brain of the whole network. In order to reduce the influence of single point fault of controller, this paper designs a simple, reliable and more available master-slave distributed system and master-slave election algorithm based on priority and non preemption. The election process is no longer limited by the number of healthy nodes. The log replication system of Raft algorithm is simplified, and a simple and efficient master-slave incremental/full data replication process is designed. Combined with the data persistence storage and recovery function, the data can not be lost after the system restart. The experiment results show that the system has realized the main functions of the main and subordinate distributed system, and the performance is better, and it can adapt to various complex application scenarios of the distributed SDN controller system.