According to the optical and magneto-optical characteristics of magnetic fluid, five kinds of common fiber magnetic field sensors are introduced, including fiber magnetic field sensor based on interference mechanism, fiber magnetic field sensor based on fiber grating structure, fiber magnetic field sensor based on evanescent wave mechanism, fiber magnetic field sensor based on surface plasmon resonance mechanism field sensor and fiber magnetic field sensor based on photonic band gap effect mechanism, various technical performances of magnetic fluid fiber magnetic field sensor are analyzed, and the technical difficulties are pointed out. Finally, the research direction of magnetic fluid fiber magnetic field sensor is prospected.

In order to improve the detection sensitivity of the external vibration signal, a system based on the combination of phase sensitive optical time domain reflectometer(Φ-OTDR) and 3D printing sensor is designed. The sensor in the system is composed of optical fiber wound in a cylindrical elastomer, which is made of 3D printing flexible material. By detecting the 20 kHz signal at 100 m, it is proved that the 3D printing sensor with integrated elastomer has the effect of enhancing sensitivity for the detection of high frequency vibration signal, and the amplitude of the demodulated signal spectrum is increased by 8 times.

The long period fiber grating must be written and used under stress. In this paper, the effects of stress on the central wavelength and attenuation depth of resonance wave during and after writing of the long period fiber grating are analyzed in detail by experimental method. It is found in the experiment that the stress has no influence on the central wavelength of the resonant wave, but has a greater influence on the attenuation depth of the resonant wave, and the influence of the stress on the performance of the long period fiber grating at different stages is different. When writing, the stress provided by 40 g weights can be used to write long period fiber grating with good characteristics and the performance of the long period fiber grating can be further improved by increasing the stress after writing.

Aiming at the optimization requirements of massive data transmission in data center optical network application scenarios, this paper proposes to use machine learning method to classify the traffic types to be sent before sending data center traffic, and introduces an improved greedy genetic algorithm(IGGA) into data center optical network reconstruction and optimization. The simulation results show that under the same node distribution, the average length of the improved IGGA is significantly reduced compared with the traditional genetic algorithm(GA), and the average length of the improved IGGA is reduced by 3.06% and 6.37% respectively in the case of 20 nodes and 50 nodes topology, and the improvement effect improves with the number of topology nodes increases.

The geoacoustic is mainly infrasonic wave whose frequency is concentrated in 0~20 Hz, which has high requirements on the sensitivity, accuracy and frequency response characteristics of the sensor, reasonable signal demodulation method is the key of sensor research. A dual wavelength single channel quadrature demodulation method is proposed. According to the interference principle of light, the sensitive mechanism of the extrinsic geoacoustic sensor based on extrinsic Fabry-Perot interferometric(EFPI) is theoretically analyzed, it makes clear that the sensor needs to meet the requirements in the linear region when working, and the simulation analysis is carried out by using Matlab software. The simulation results show that the algorithm can avoid the influence of external environment on the output results, and can accurately demodulate the original signal, which proves the feasibility of the demodulation method.

Modulation technology is the key factor affecting the performance of space optical communication system. Comparing the comprehensive performance of several typical intensity modulation schemes in a unified scale, five performance expressions of average symbol length, bandwidth requirement, bandwidth utilization, average transmit power and transmission capacity of 19 typical intensity modulation schemes are derived, and the numerical simulation is carried out. The comprehensive performance structure chart of each modulation mode is drawn, and the applicable scenarios of different modulation modes are given.

In order to further improve the transmission quality of the wireless communication system, a new type of radio frequency bandpass filter based on two-dimensional photonic crystal is proposed. The filter is composed of a line defect waveguide and an Aubry-André-Harper(AAH) resonator. By changing the radius of the dielectric column between the AAH resonator and the output waveguide, the coupling coefficient between them is increased, realizing the filtering of the radio frequency band at 1666 μm. The simulation results show that the radio frequency filter has excellent performance, the center wavelength of the passband is 1666.64 μm, the transmittance is 0.99, the passband insertion loss is 0.06 dB, and the quality factor Q value is 1×104. The device is small in size, simple in structure.

In order to solve the problems of signal attenuation and capacity limitation in optical fiber transmission, PbS doped ring core fiber is prepared by improved chemical vapor deposition(MCVD), and a reverse pump light amplification experimental device is built to realize broadband amplification in C band, which provides the possibility for the realization of less mode fiber amplifier by using PbS doped fiber. The experimental results show that the switching gain of sample fiber in C-band increases with the increase of pump power, the switching gain decreases with the increase of signal power. When the pump power is 750 mW and the signal power is 0.003 nW, the switching gain of the sample fiber in C-band is about 8 dB.

Due to the uneven output gain and low gain of single pump Raman fiber amplifier(RFA), the performance of optical fiber communication system becomes worse. A forward three pumps RFA is designed. Focusing on the influence of the appropriate number of pumps, pump wavelength and pump power on the output gain of RFA, and combining with OptiSystem software, the gain of L-band RFA is optimized and simulated. The simulation results show that the designed RFA achieves a gain of more than 10 dB in L-band and is relatively flat. The maximum gain is 18.9 dB and the maximum noise figure is 8.0 dB.

In order to improve the performance of the hot wire fiber anemometer, based on the metal film fiber Bragg grating(FBG) hot wire fiber anemometer, the FBG cladding diameter of the anemometer is reduced from 125 μm to 71.6 μm by reducing the thickness of the FBG cladding, the thin cladding FBG hot wire optical fiber anemometer is compared with FBG conventional anemometer. The results show that the initial temperature of FBG hot wire fiber anemometer is increased by 48.3%, the sensitivity of airflow velocity measurement is significantly increased by 61.2%, and limited by the wind tunnel used, the maximum wind speed test range is 20 m/s.

Because thermal polarization will destroy the center inversion symmetry of silica glass fiber, the second-order optical nonlinear effect and linear electro-optical effect is produced. Moreover, the larger the second-order nonlinear effect is, the higher the application value of optical devices will be. In this paper, a dumbbell shaped double hole silica glass fiber is designed. The carrier model and the finite element method is used to analyze the motion of ions and the formation process of the space charge region in the thermal polarization process of the dumbbell shaped double hole silica glass fiber. The experimental results show that the second-order nonlinear coefficient of the dumbbell shaped double hole silica glass fiber at the core center is 0.3204 pm/V, which is 0.0678 pm/V higher than the circular double hole fiber.

In order to lock the optical frequency comb to the atomic clock to achieve high precision and stability of the optical frequency comb, an integrated repetition rate locking system is proposed. Fiber loop optical microwave-phase detector (FLOM-PD) is used for direct frequency and phase discrimination between light wave and microwave. At the same time, the precise feedback control module is developed, its basic principle is described, and the locking system is built. The laser pulse repetition rate data after locking is collected by high-precision frequency meter. The experiment results show that the short-term stability and long-term stability of the system can reach 8.71×10-12 / s and 4.95×10-14 / 1024 s respectively, which realizes the integration of the whole system.

In order to build a higher quality central private network and meet the needs of central users for high speed, high reliability and high utilization, a new optical transport network (OTN) technology --Liquid OTN is used to carry the existing network services. The frame structure of Liquid OTN and the advantages of Liquid OTN over traditional OTN and multi service optical transport network (MS-OTN) are introduced. This paper verifies the application effect of Liquid OTN equipment, the results show that Liquid OTN equipment has the characteristics of high speed, low delay and high expansion.

Advanced modulation technology, channel equalization technology and channel coding technology are the three key technologies to improve the performance of optical transmission system. The optical transmission experiment is carried out by using double binary(DB) modulation technology, feed-forward equalization(FFE) technology and low-density parity check (LDPC) coding technology. After 25 km standard single-mode fiber transmission, the data transmission at 50 Gb/s rate is completed on the 12 GHz optical receiver. The experimental results show that FFE can effectively improve the performance of optical transmission system, and the decoding threshold of LDPC code is around 2×10-2.