In order to reduce the complexity and improve the stability of indoor power line communication and visible light communication(PLC-VLC) systems, an improved PLC-VLC hybrid network system based on orthogonal frequency division multiplexing(OFDM) is proposed. By improving the structure of dual PLC modulator and light emitting diode (LED), the complexity of traditional hybrid network system is reduced. The simulation platform of PLC-VLC hybrid system is built, and the performance of signal spectrum, eye map and bit error rate are simulated and analyzed. The simulation results show that the proposed improved PLC-VLC hybrid network system based on OFDM has no distortion in the conversion of electrical signal and optical signal, high signal transmission accuracy and good system performance.

Aiming at the problems of low reliability and poor user fairness in non orthogonal multiple access visible light communication(NOMA-VLC) system based on Fourier transform optical orthogonal frequency division multiplexing(FFT-OFDM), a carrier modulation method called lifting wavelet transform(LWT) is proposed to establish a NOMA-VLC system based on LWT-OFDM. The signal processing process in the system is introduced, and an indoor space experiment environment of 5 m×5 m×3 m is constructed. The experimental results show that compared with the NOMA-VLC system based on FFT-OFDM, when the order of orthogonal amplitude modulation increases from 4 to 64, the required signal to noise ratio(SNR) value is lower, at least 4.4 dB lower, when the average bit error rate of the proposed system reaches the threshold of 3.8×10-3. User performance differences do not change significantly or even remain unchanged.

Aiming at the demand of local distributed time synchronization, a short range distributed time synchronization scheme based on the combination of optical fiber and visible light is proposed. Combining the advantages of high accuracy of optical fiber time synchronization and high flexibility of visible light time synchronization, a corresponding time synchronization terminal is designed and distributed experiments are carried out. The experimental results show that when the length of the fiber link is 3 km, the 3σ clock difference between slave and the main end is better than 448 ps, the second stability of the time synchronization is better than 150 ps, and the 10 000 second stability is better than 4 ps. When the length of the optical fiber link is 1 km and the visible light link length is 5 m, the 3σ clock difference between the slave end of the visible light time synchronization and the primary end of the optical fiber time synchronization is better than 1.8 ns, the time synchronization stability is better than 400 ps in seconds, and the time synchronization stability is better than 15 ps in 10 000 seconds.

In order to further optimize the liquid Terahertz radiation source induced by femtosecond laser, a femtosecond laser-induced liquid line radiation Terahertz wave experimental system was designed. Combined with quantum chemistry calculation and femtosecond laser-induced liquid line radiation Terahertz wave experiment, the relationship between the microscopic and macroscopic characteristics of the excited medium and the Terahertz electric field was studied. The experimental and calculated results show that the Terahertz electric field is negatively correlated with band gap width and dipole moment. The nonlinear trend of Terahertz electric field with solution concentration is related to the density and Reynolds number of the medium, and the optimal volume fraction of Terahertz wave electric field is 40%.

In view of the few studies on the positive curvature of fiber cladding tube, a new Terahertz antiharmonic fiber based on the positive curvature regulation of fiber cladding tube is proposed. Firstly, the structure of Terahertz anti-resonant fiber with circular cladding tube and semi-circular semi-elliptical cladding tube is studied, and the influence of positive curvature on the limiting loss of fiber and the main mechanism are analyzed. Then, the structure of Terahertz antiharmonic fiber is optimized, and the two-layer cladding tube structure is adopted in the fiber gap. Finally, the loss limiting performance of three kinds of fiber structures is simulated, and the single-mode characteristics of the new Terahertz antiharmonic fiber are analyzed. The simulation results show that compared with other fiber structures, the new antiresonant THz fiber has a limited loss of 10-5 dB/m, and maintains good single-mode characteristics in 2.5~3.1 THz band.

In order to identify and deal with optical path faults timely and accurately, and realize transparent and real-time network intelligent management, an optical channel performance analysis method based on cross recurrence plot theory is proposed for optical channel state performance monitoring. First, the method uses cross recurrence plot to visualize the state parameters of adjacent channels to analyze the dynamic characteristics of the channels. Then, the synchronization characteristics of the two sequential systems are quantified by quantitative analysis method. The simulation results show that the performance of optical channels has similar dynamic morphology with the state parameters of adjacent channels, which confirms their potential correlation characteristics.

In order to solve the problem of poor equalization ability of traditional continuous time linear equalizer(CTLE), a new 25 Gb/s CTLE circuit based on 40 nm complementary metal oxide semiconductor(CMOS) technology is proposed, which adopts parallel inductance peaking, negative capacitance zero compensation and output buffering technology. The influence of shunt inductance peaking and passive devices on CTLE frequency characteristics is introduced. Finally, the new CTLE circuit is simulated. The simulation results show that when the data transmission rate is 25 Gb/s, the equalized bandwidth of the CTLE extends from 8.5 GHz to 21.3GHz. The peak-to-peak differential voltage of the output signal is 410 mV, and the power consumption is 8.62 mW. The overall circuit layout area is 667 μm×717 μm, which has the characteristics of low power consumption and small area.

In order to solve the problem of irreversible damage to the high-speed signal source caused by the conduction/cutoff of the direct current(DC) source or hot swapping of the link during the testing process of traditional T-type biases(Bias-T) in silicon-based high-speed modulators. Firstly, the causes of the problem and the advantages and disadvantages of conventional solutions are analyzed, and then an active Bias-T circuit for silicon based high speed modulator testing is designed. This circuit utilizes the characteristics of transistors in microwave amplifier chips on the basis of traditional Bias-T to isolate the impulse voltage generated by the DC source during feed on/off or hot swapping. Finally, simulation design and testing are conducted on the active Bias-T circuit. The test results show that the bandwidth of the circuit is greater than 25 GHz and the pulse voltage is about ±0.055 V, which eliminates the risk of damage to the signal source equipment.

In order to further improve the energy utilization rate of the system, a fiber optic energy supply system based on intelligent charging control is designed. The system uses a charging control device to stably supply energy to the rear load and flexibly regulate the charging mode of the energy storage module, so as to realize the rapid storage and rational utilization of the remote excess energy, and realize the real-time regulation of the system's working state based on the feedback signal. The experimental results show that the system can automatically adjust the output power of the local laser source according to the remote load and the working state of the device in different scenarios, so as to ensure the safe operation of the energy supply system. When the light energy supply is insufficient, the stored energy can be used as backup energy for emergency energy supply to the sensor or application equipment.

In order to achieve rapid capture of low-rail IoT signals under the conditions of high dynamic and low signal-to-noise ratio, a partial matching filter-fast Fourier transform (PMF-FFT)improvement algorithm for rapid capture of low-rail IoT signals is proposed. First of all, the ephemeris information is used to predict the Doppler frequency bias and narrow the frequency domain search range; then, the scallop loss of PMF-FFT algorithm is overcomed by zero padding and windowing. Finally, the frequency domain differential incohere accumulation is used to improve the output gain under low signal-to-noise ratio. The simulation analysis shows that the proposed algorithm can improve the detection probability of low-orbit iot signal when the signal-to-noise ratio is -25~-15 dB, and the search range is reduced from 15~35 kHz to 24.8~25.2 kHz.

In order to further explore the efficient generation methods of high order and fractional order vortex light, relevant computational programs are used to simulate the phase hologram of vortex light, and the optical path for generating vortex light using phase holography is constructed. The optical field distribution characteristics of integer and fractional order vortex light are studied. The experimental results show that when generating vortex light with orbital angular momentum topological charge l=1~200 integer orders, the central dark spot of the vortex beam pattern will increase with the increase of topological charge within a certain range. After exceeding a certain numerical range, the quality of vortex light limited by instrument parameters will decrease. When generating fractional order vortex light with l=8.1, 8.4 and 8.8, the phase of the vortex light exhibits a fractional distribution, and the radial gap gradually evolves towards integer order as the fractional order topological charge increases.

Aiming at the problems of insufficient communication broadband and low contact wear life of traditional slip ring, an off-axis disc type wireless smooth ring based on space laser communication is designed and a prototype is developed. The smooth ring uses optical tracking simulation technology to arrange four infrared emitters uniformly and equally at four corners of the smooth ring, so that the optical power can be received continuously and stably when the receiving end is rotating. The optical simulation and performance test results show that the receiving power of the off-axis disc type wireless smooth ring is -28.3~-29.2 dBm when the transmission distance is 20~200 mm, which meets the requirement of detector sensitivity(about -30 dBm). In the 0~500 r/min rotation environment, the bit error rate will increase with the increase of transmission distance, but the overall bit error rate is less than 10-6.

Aiming at the problems of large number of channels, large volume and power consumption and low integration of traditional microwave photonic products, an ultra-compact package optical/electrical conversion array module based on microwave photonic hybrid integrated packaging technology is designed. The photonic device, microwave chip, adjustable attenuation chip and circuit system are sealed into a shell. It can realize many functions such as optical/electrical conversion, signal amplification, attenuation adjustable and equalization in ultra-compact space. The test results show that the photoelectric responsiveness of the module is higher than 0.8 A/W in the 2~18 GHz band. The mean value of S21 for the six channels is -3.5 dB, the flatness of each channel is within ±1.5 dB, the channel isolation is greater than 55 dB, and the standing wave reflection is less than 1.7 dB.

In order to accurately measure the dispersion of quasi-transverse wave(TE) and quasi-transverse magnetic wave(TM) in meter-level linear slit waveguides, a dispersion-measuring optical path of Mach-Zehnder interferometer(MZI) is designed. The measurement principle of phase fitting method and balanced wavelength method is introduced, and the measurement is carried out in combination with the measurement optical path. The measurement results show that the accuracy of dispersion measurement can be further improved by removing the crosstalk noise between polarization modes. The dispersion of the waveguide can be effectively controlled by adjusting the slot size. When the slot thickness is 0.1 μm, the waveguide has near zero and flat dispersion in the wavelength range of 1 440~1 640 nm.

Fiber optic endoscope is widely used to detect damage in small space of complex structures, but due to its inherent characteristics and external noise, the acquired images show a honeycomb grid, and there is about 30% barrel distortion. For this problem, a calibration method based on optical fiber endoscope image is proposed. Firstly, a freely moving calibration system is designed, and then the optical fiber bundle in the calibration plate image is processed by Gaussian filtering, binarization processing, mark point identifying and distortion correcting. Finally, the calibration method is used to calibrate and correct different types of calibration plate images taken by optical fiber endoscope. The experimental results show that the proposed calibration method is suitable for correcting and identifying of various scenes and images of different quality, and the measurement error is only 10 μm.

In order to explore a rapid and accurate detection method for honey containing uncine-kisses, mid-infrared(MIR) spectral images of 216 non-toxic and uncine-toxic honey samples from different regions are collected by MIR spectrometer. The 800~1 800 cm-1 band of the spectral images is selected as the main research band. Principal component analysis and partial least square regression(PLS-DA) algorithm are used to establish the identification model of hook-free and non-hook-free, and the prediction results of different data preprocessing methods are compared. The simulation results show that the identification model established after the first derivative pretreatment has the best identification effect, and the identification accuracy reaches 90.74%.

In order to meet the needs of current power communication operation and maintenance, an intelligent optical fiber on-line dynamic monitoring system based on optical power is proposed. A monitoring center and a front-end module are set up at the main station of the system, and the link is connected to the complete set of terminals of the station through the automatic protection unit optical power monitor(OLP), and then the optical power monitor(OPU) is used to capture the online optical power value and compare it with the preset threshold through the IP network to realize the intelligent online dynamic monitoring of the system. The practical results show that the system can quickly protect the faulty link and locate it accurately within 40 ms.

In view of the limitations of current blood pressure sensors, such as electromagnetic interference, large size and difficult integration, a micro optical fiber sensor for blood pressure detection in interventional catheterization is proposed. By adopting the principle of lateral forces on a suspended optical fiber, the sensor can be flexibly integrated into a medical catheter to achieve the fixed-point intravascular pressure measurement. A 4 mm external diameter micro optical fiber blood pressure sensor is fabricated and packaged by light-curing 3D printing technique. The static and dynamic characteristics of optical fiber sensor and the application test of simulated vascular pressure are carried out. The experimental results show that the sensitivity and linearity of the micro optical fiber blood pressure sensor are 0.723 pm/ kPa and 0.996 respectively in the range of -50~50 kPa, and the dynamic test results are in good agreement with the commercial sensors, and the feasibility of the operation is verified on the blood vessel heart model.

In order to meet the requirements of safe operation and external wall temperature monitoring of gasifier, based on the principle of Raman scattering effect and the characteristics of distributed optical fiber system, a novel temperature measurement method for on-line monitoring of gasifier external wall temperature is proposed, A kind of armored polyamide high temperature resistant distributed optical fiber sensor system using seamless steel tube as protective layer is designed. The temperature uncertainty experiment and data analysis of the sensor system are carried out. Finally, the temperature of the high temperature resistant optical fiber is tested on the experimental platform of gasifier outer wall temperature rise. The experimental results show that the temperature measurement range of the distributed optical fiber sensing system is 0~300 ℃, and the temperature measurement accuracy is ±2 ℃, the abnormal high temperature can be distinguished.

Optical time domain reflectometer(OTDR) on-line detection at the transmitter will affect the service signal, so it is rarely used in practical engineering. In order to explore the specific impact of OTDR at the transmitter on the service signal light, the relationship between the dynamic range of OTDR and the power of optical pulse has been analyzed theoretically. The influence of on-line detection of OTDR at the transmitter on traffic signal light and its reasons are studied experimentally based on 200 Gb/s and 2 Mb/s transmission system. The experimental result shows that the influence of the OTDR on-line detection on the communication service is related to the incident optical power, the dynamic range of the OTDR and the system margin. The strong optical pulse which is generated by OTDR at the transmitter will cause the fluctuation of intensity and the time-domain pulse, which will affect the communication service.

Increasing the transmited pulse width of optical time domain reflectometer(OTDR) may lead to saturation effect of ava-lanche photodiode(APD) in the detection circuit of OTDR, and makes the measured curve flat roof effect, which will submerge the short-range event results. To solve this problem, this paper proposes a multi-pulse width combined measurement method, the measurement results are software spliced to achieve a longer measurement distance under the condition of the hardware configuration unchanged, and the near-end events will not be submerged by the flat roof due to the saturated flat roof effect, the dynamic range of OTDR measurement is improved.

The block-averaging reference phase estimating algorithm is able to reduce the variance of phase compensation noise effectively in the continuous-variable quantum key distribution. In order to optimize the performance of the block-averaging reference phase estimating algorithm, according to the mathematical model of phase drift variation, the mean square error characteristics of the algorithm are analyzed theoretically, and the optimal block length is obtained. Simulation results show that the variance of phase compensation noise can be reduced by 72% under the optimal phase estimation, so that the distance for generating secure key can be improved most significantly.

The transmission fiber is affected by the change of ambient temperature and vibration, which will cause the phase drift of radio on fiber frequency signal, and lead to the decrease of time-frequency transmission accuracy. In order to reduce the influence of phase drift on transmission system, the optical fiber phase drift detection and phase compensation experiment verification are caried out by using the optical fiber phase-stabilized transmission technology based on fringes counting method of optical fiber interferometer. The experimental results show that the natural phase drift of 168 m transmission fiber for 28 h is 32.3 ps, and the phase drift is reduced to 1.29 fs by using piezoelectric ceramics and temperature-controlled optical fiber to compensate the natural phase.

In order to suppress the nonlinear effect of the optical transmission system, an improved 32-channel quadrature pulse shaping dual-phase conjugate twin wave (QPS dual-PCTW) nonlinear suppression scheme combining high-order modulation format and nonlinear separation technology is proposed. With the joint simulation of Optisystem and Matlab, a 32-channel nonlinear separation model with or without QPS dual-PCTW scheme under 16-order quadrature amplitude modulation(16QAM) and 64QAM is built, and the system's bit error rate is analyzed through simulation under different conditions to study the suppression of nonlinear effects gained by this scheme. The simulation results show that whether the QPS dual-PCTW scheme is used or not, the four wave mixing(FWM) effect has a greater impact on the system performance, when the QPS dual-PCTW scheme is used, the main factor affecting the system performance is inter symbol interference.

According to the requirements of time synchronization in long haul optical fiber links, the bidirectional Erbium doped fiber amplifiers(EDFA) are used to extend the transmission distance. This paper introduces the composition of the optical fiber time transfer system. By constructing the time delay model of the optical fiber time transfer link, it focuses on the research and analysis of the asymmetric time delay in the long-distance optical fiber time transfer system, and details the accurate calibration method. Finally, an experimental platform is built to test and verify the time transfer performance. The test results show that the time synchronization accuracy is -47 ps, and the synchronization accuracy is 128 ps, the 600 km sub nanosecond optical fiber time transmission is realized.

In order to meet the demand of emergency communication data transmission outside nuclear power plant, the application research of long-distance non relay transmission technology of optical fiber is carried out. Firstly, the paper introduces the limited factors and safety factors of long-distance relay free transmission of optical fiber, and points out the solutions respectively. Then, a long distance relay free optical transmission method without remote optical pump amplifier(ROPA) is proposed and verified by experiments. The experimental results show that the non relay transmission distance of optical fiber link is 252.15 km, which can meet the requirements of ultra long distance data transmission and safety of emergency communication command network of nuclear power plant.

In order to further improve the tunable range of the tunable optoelectronic oscillator based on Mach-Zehnder interferometer(MZI), the influence of the relative power ratio of the two arms and the arm length difference of the two arms in the MZI on the transmission performance of the optoelectronic oscillator is discussed and analyzed. Through simulation analysis, it can be known that when the relative power ratio of the two arms of the MZI is 0.5, when the arms length difference changes between 12 mm~50 cm, the optoelectronic oscillator can output a single frequency microwave signal in the range of 0.411~16.892 GHz.

In order to study the influence of refractive index profile structure on optical properties of G.657.B3 fiber, the refractive index profile with the depressed structure and the corresponding structural parameters (such as b/a value, c, Δnc- and Δn+) are designed. Meanwhile, appropriate vapor axial deposition(VAD) method, melting process and drawing conditions are used to improve the bending loss of the optical fiber and meet the requirements of cut-off wavelength, mode field diameter and low water peak. The optical fiber preform prepared by the optimized process is drawn and tested. The results show that the attenuation of the optical fiber decreases to 0.278 dB/km at the wavelength of 1383 nm, when the bending radius is 5 mm and one circle, the typical macro-bending loss are 0.081 dB and 0.188 dB respectively at the wavelength of 1550 nm and 1625 nm, which fully meet the requirements of ITU-T G.657.B3.

Aiming at the problem of the phenomenon that the system performance of free space optical(FSO) communication drops sharply and the difficult problem of attenuation data acquisition in the fog environment, this paper sets up an innovative indoor FSO communication system to simulate the transmission of laser in foggy weather. The attenuation condition of FSO communication in foggy weather is studied and the channel probability model of the indoor FSO communication system is constructed. In the indoor FSO communication system, this paper simulates the 1550 nm wavelength laser under different visibility of transmission attenuation condition, analyzes the statistical characteristics of FSO signals under different visibility, chooses Gamma fitting distribution to establish channel probability model. By using intensity modulation /direct detection and on-off keying modulation method, the bit error rate of the FSO communication system under different link length、different visibility and different transmission power is deduced. The experiment verifies the feasibility of the analog channel.

To reduce the difficulty of receiving visible light signals from mobile phone cameras, a new light-emitting diode(LED) light array visible light communication transmitting system is developed. A lamp array arrangement structure combining communication lamp and positioning lamp is innovatively proposed, and a special encoding method of frame spacing loading a full light screen is designed to ensure the illumination effect while realizing the parallel transmission of optical information, Matlab simulation software is used to simulate and analyze the lighting and communication effects of the system, and the communication effect is tested experimentally. The results show that the transmission system can meet the lighting requirement by interspersing one frame of full bright picture between two effective information transmissions, and the transmission bit error rate is low, and the communication performance is good.

High precision and stable beam tracking is the premise of establishing free space laser communication link. An improved firefly algorithm is introduced to optimize the parameters of the proportional integral differential(PID) controller. At the same time, the model of the DC torque motor system is established. The optimized PID controller is applied to the system, and the experiment is carried out on the six dimensional simulation platform. The results show that for the same system, compared with the Ziegler and Nichols(Z-N) method, the optimal PID controller has better performance, the response speed, bandwidth and tracking accuracy of the improved firefly algorithm are improved by 40%, 33.3% and 25% respectively.