Aiming at the simultaneous influence of magnetic field and temperature on the magnetic fluid current sensor, optical current sensor based on magnetic fluid is studied and the experimental system of temperature characteristics of the sensor is built. The results show that in the range of 26 ℃~74 ℃, the thermal lens effect of magnetic fluid causes a temperature gradient, and the temperature of the constant temperature water bath increases the Brownian motion of the magnetic, therefore, the transmittance of the magnetic fluid optical current sensor decreases as the temperature of the constant temperature water bath increases.

In large fiber Bragg grating(FBG) sensor networks, due to the limited bandwidth of light sources and the large number of FBG sensors, the problem of spectral overlap will occur. Therefore, improving the reuse ability has become a key problem in the design of sensor networks. In this paper, the experiment and simulation analysis of multi-FBG transmission system are carried out by combining spectral reuse with quantum particle swarm optimization(QPSO) algorithm. Compared with the traditional particle swarm algorithm, the parameter setting of the QPSO algorithm is relatively simple, and the ability of particle search for the optimal solution is greatly improved. The paper analyzes the demodulation results of QPSO algorithm and adaptive mutation quantum particle swarm optimization(AMQPSO) algorithm, and compares the demodulation accuracy and time of the two algorithms. The demodulation error of AMQPSO algorithm in multi-FBG reuse system is not more than 3 pm, the accuracy of temperature measurement is up to 0.3 ℃, and the demodulation time is not more than 5 s. It solves the problem of partial overlap and complete overlap in multi-FBG system.

For the collection of human health data, which requires multi-parameter and flexible safety sensor, this paper proposes to use the flexible sensor based on fiber Bragg grating(FBG) to detect the temperature, pressure and motion state of the human body. The effects of temperature and pressure on the drift of FBG reflection wavelength and the influence of pressure on the optical power of the fiber are theoretically analyzed, the temperature sensing model, pressure sensing model and human motion model are established. Sensors based on flexible substrates have improved performance in both temperature sensing and pressure sensing. Finally, the flexible base grating sensor is used to monitor the temperature, pressure and motion state of the human body.

The vertical distance between the vibration source and the sensing channel is one of the important indicators concerned by the operators of optical cables and cables. It has important guiding significance for the safe disposal of the transmission line. A calculation method of the vertical distance between the vibration source and the sensing channel based on distributed vibration monitoring system(DVS) is proposed. Through real-time acquisition of cable signal data, the attenuation characteristics of vibration wave are analyzed, the appropriate calculation model of vibration wave amplitude spectrum is selected, and the distribution equation of the amplitude spectrum and the distance between the vibration source and the vertical distance is given, as well as the approximate calculation method of the vertical distance. Experiments show that the vertical distance error calculated by this algorithm is small, which meets the engineering design requirements and has high practical application value.

Aiming at the problem of limited input power of 10 Gb/s ultra-long distance optical transmission system, a method to suppress stimulated Brillouin scattering(SBS) and improve input power is proposed. This method effectively combines the two ways of improving SBS threshold, which are laser low frequency disturbance and signal light phase modulation, and carries out comparative experiments. The experimental results show that this method can effectively improve the SBS threshold and increase the input power of 10 Gb/s ultra-long distance optical transmission system from 12 dBm and 17 dBm to 19 dBm, thus further extending the system's relay-free transmission distance.

Frequency-converter is one of the key technology of the microwave system, however, the key performance indicator of the technology is hard to break through, which is limited by the electron devices. A novel method of microwave mixing based on dual-parallel electro-optic external modulators is proposed in this paper. In this paper, the key components such as mixing technology, electro-optic modulation and optical frequency tupling are designed. Finally, a simple experimental system is built to verify the key parameters, and the system is simulated by using Matlab.

In order to improve the scheduling efficiency of the synchronous digital hierarchy(SDH) signal mapped to the optical transport network(OTN) signal in the OTN domain, a new service mapping method SDH over OTN(SoO) model under the packet optical transport network(POTN) system architecture is proposed to carry the SDH service. Under the SoO service mapping model, 4 synchronous transport modules(STM-4) signal is mapped to the low order optical channel data unit (ODU0) through a general frame process and timing transparent transcoding, and then multiplexed to the ODUk transmission signal. Compared with the traditional SDH service mapping OTN signal mode, the SoO model can effectively improve the SDH signal scheduling efficiency, which is 2~8 times that of the traditional mode. The network test method is used to verify the feasibility of the mapping method, and has the advantages of low power consumption, low latency, and flexible scheduling.

In order to solve the problem of loss measurement of ultra-long span fiber transmission, this paper proposes a new measurement method based on digital linear frequency modulation optical time domain reflection(DLFM-OTDR). This method can solve the contradiction between the maximum measurement distance and the spatial resolution. The DLFM-OTDR uses direct modulation and direct detection at the transmitter and receiver respectively. The structure is simple and requires no additional optics. The method introduces the short-term fractional Fourier transform (STFrFT) for signal processing and noise filtering. the paper uses the DLFM-OTDR development board to perform experimental tests on the actual fiber transmission links. The measurement results of the fiber link length of 2×150 km are taken as an example, the experimental results show that the DLFM-OTDR is especially suitable for monitoring the ultra-long fiber link under the condition of long single span.

In order to provide design basis for blue-green laser communication system, a standard atmospheric attenuation model in mid-latitude region was used to analyze the effects of weather phenomena, turbulence intensity, divergence angle and receiving aperture on link margin, signal-to-noise ratio and bit error rate, combined with atmospheric attenuation, geometric attenuation and atmospheric turbulence. The analysis results show that the link margin is related to divergence angle and receiving aperture, while the signal-to-noise ratio and bit error rate are only related to receiving aperture. At the same time, on sunny days, the smaller the divergence angle and the larger the receiving aperture, the larger the link margin is; the weaker the turbulence intensity, the larger the receiving aperture, the larger the SNR is and the smaller the bit error rate is.

The performance of multi-cell systems has been seriously affected by inter-cell interference. In order to reduce the influence of inter-cell interference, the performance of multi-cell and multi-user multiple input multiple output visible light communication (MIMO-VLC) system is studied. The angle diversity receiver based on the hole is used as the receiving device, and the interference area is optimized by selecting the appropriate LED configuration, and two multi-cell implementation schemes are discussed. The first is dynamic cell division, and the second is photodetector selection(PDS) to eliminate inter-cell interference. The simulation results show that: when there are users in the interference zone in the cell, the dynamic cell division method has better bit error rate(BER) performance for the users in the cell, but the location of users in this cell will affect the performance of users in other cells, and its computational complexity is high. For PDS method to eliminate inter-cell interference, the BER performance of users in a cell is not affected by the location of users in other cells, and its computational complexity is low. When users are all in the non-interference zone, the BER performance of the two methods is the same.

Based on the national natural fundkey project "Intrinsic security optical communication theory and technology research", three prior art solutions for physical layer key distribution are described in detail. In order to achieve high-rate physical layer key distribution compatible with existing communication devices, this paper proposes a physical layer key distribution technology based on fibre channel features. The transmitter and the receiver extract the quantized generation key by using the double-ended loopback measurement bit error rate method based on the fiber channel transmission bit error rate characteristic and key distribution technique. The research results show that the optical fiber transmission rate is 10 Gb/s and the transmission distance is over 200 km. When the physical layer secure key generation rate reaches 400 kb/s, the bit error rate of secure keys does not exceed 2%.

To eliminate multiple access interference(MAI) noise in optical time division/code division multiple access igital communication systems, a novel all-optical threshold decision technique based on cross gain modulation(XGM) effect in distributed feedback(DFB) lasers cavity is proposed. By injecting optical digital pulse signal into DFB laser, XGM effect appears inside the laser. Using optical bandpass filter(OBPF) to filter out the new spectrum produced by XGM effect can eliminate MAI noise in the signal, thus improving the reception performance of digital signal.

In order to improve the transmission capacity of the optical communication system, this paper proposes a new type of 12 channels wavelength-mode-polarization division hybrid multiplexing system, and the wavelength division multiplexing device is combined with the mode division multiplexer, so that the system can be adapted to the wavelength-mode division hybrid multiplexing. Signals of 12 channels are transmitted by the few-mode fiber, and the output signal is decompressed with a constant mode algorithm. Through the VPI transmission Maker simulation platform, the influence of wavelength interval, transmitter output power and laser line width on the performance of the system is analyzed. The simulation results show that under the condition that the signal-to-noise ratio is 20 dB and the transmitter output power is 0 dBm, using 2 wavelengths and 6 modes, each mode carries the 25 Gb/s data, and the bit error rate is in the 10-4 volume level to realize the 25×2×6 Gb/s polarization division multiplexing-binary quadrature amplitude modulation(PDM-4QAM) signal transmits 10 km without relaying.

Aiming at the poor quantization performance of low bit digital analog converter(DAC) in intensity modulation direct detection-filter bank multi-carrier(IMDD-FBMC) system, a non-uniform quantization scheme based on signal distribution estimation is proposed. The scheme uses the non-linear programming method based on FBMC signal distribution to obtain the quantitative step when the quantization error is minimum, and then improves the performance of IMDD-FBMC system based on low bit DAC. The simulation results show that the proposed scheme can improve the BER performance of the IMDD-FBMC system by 15.9~60.7 times under the condition of 3~5 bit quantization number compared with the uniform quantization scheme, and the quantization scheme based on signal distribution can reduce 1~2 bit quantization number and reduce the system cost under the condition of ensuring the system performance.