In order to solve the requirement of positive real value of the signal at the light-emitting diode(LED) transmitting end in the optical orthogonal frequency division multiplexing(OOFDM) system, according to the characteristics of fast Hartley transform(FHT) "Real in Real out", FHT is used instead of fast Fourier transform(FFT), quadrature amplitude modulation(QAM) mapping is applied to FHT-based asymmetric limiting direct-current biased OOFDM system, and simulation experiments are carried out. The simulation results show that the FHT system has better bit error performance than the underwater visible OFDM communication system with the same frequency band utilization under the condition of the same underwater background noise.

The existence of thermal noise and shot noise will greatly reduce the positioning accuracy of indoor visible light positioning system. In order to improve the positioning accuracy, a visible light location method based on received signal strength is proposed. Firstly, the adaptive filtering method is used to greatly filter the noise in the received signal, and then the cross-correlation detection method is used to further filter the noise, and the original signal strength is extracted. Finally, the coordinates of the object to be measured are estimated by the least square method. The simulation results show that in a 4 m×4 m×3 m room, the positioning errors of 1681 detection points are within 0.01 m, and the positioning errors are basically the same under different signal-to-noise ratios, therefore, the visible light location method has a certain ability to suppress noise.

In order to further optimize and improve the fixed mode of optical fiber sensor, an extrinsic Fabry-Perot(F-P) optical fiber sensor with metal solder chip is designed and experimentally observed. The failure mechanism of F-P optical fiber sensor with different welding fixed mode at 1200 ℃ high temperature is studied and analyzed. The experimental samples that failed under 1200 ℃ high temperature are observed and analyzed. The finite element analysis method is used to simulate and calculate the experimental samples and the actual spectral signal changes are combined to study the specific failure process. The result show that different welding fixed mode will have different mechanical effects on the sensor, which will affect the life of the sensor.

In order to obtain the strain distribution law of arch rib of arch bridge under different stress conditions, the arch rib strain distribution under different loads is studied by establishing the finite element model and using the distributed optical fiber sensing technology based on optical frequency domain reflection(OFDR). The results show that the distributed optical fiber sensor based on OFDR pasted on the surface of the arch rib can not only accurately reflect the strain distribution law of the arch rib under different load conditions, but also obtain the strain distribution changes of the arch rib before and after the damage of the suspender, and locate the damage location of the suspender.

A large area avalanche photodiode(APD) receiving circuit in visible light band is designed to solve the problem of small amplitude and easy distortion of the output signal when the photodetector detects weak optical signal. The circuit includes a large area APD detector, a trans-impedance amplifier(TIA) and a subsequent weak signal processing circuit. The experimental results show that the designed large-area APD receiving circuit can realize 60 Mb/s visible light information acquisition, and the sensitivity is as low as -35 dBm. The weak signal processing circuit has good ability of following and shaping recovery.

Aiming at the degradation of the output performance of optical fiber amplifier in irradiation environment, the photoannealing experiment of optical fiber amplifier after irradiation damage is carried out. Firstly, the influence of radiation on optical fiber amplifier is introduced. The irradiation experiment is carried out when the total irradiation dose is about 280 krad. It is known that the radiation will reduce the output power and optical signal-to-noise ratio by 7 dB and 18 dB respectively. Then, according to the mechanism of photoannealing, the photoannealing experiment of fiber amplifier is carried out. The experimental results show that the radiation-induced loss of the fiber amplifier is reduced by optical annealing. Compared with that before annealing, the output power of the amplifier is restored by 5.2 dB and the output OSNR is restored by 13 dB.

Aiming at the problem that the risk warning of optical communication network equipment cannot be analyzed manually, a failure prediction algorithm of equipment based on user profile and deep learning algorithm is proposed. Based on data collection and data enhancement, the device health profile is constructed, and the label sequence associated with the equipment failure is extracted from the original data containing dirty data and inconsistent format, and the sequence data is fed into the deep learning model to obtain highly accurate failure prediction results. The simulation results show that this algorithm can construct the equipment health profile based on the original equipment data and train the deep learning model in real time, and obtain the accuracy rate of equipment failure prediction close to 100%. Compared with the algorithm of full label sequence and the algorithm without data enhancement, the proposed algorithm improves the accuracy rate of failure prediction by 7.8% and 3.3%.

In order to solve the problem of resources allocation caused by operators sharing network resources, this paper proposes an online bandwidth resources allocation algorithm based on deep reinforcement learning(DRL). The algorithm maps multi-tenancy passive optical network(PON) system to DRL model. The DRL agent interacts with the environment to make decisions for each pending bandwidth request and the current remaining bandwidth, and constantly updates the policy parameters until the model converges, so as to complete the algorithm optimization. A simulation system is built to verify the feasibility of the algorithm. The simulation results show that the proposed algorithm can effectively improve the utilization of bandwidth resources.

In order to improve the survivability of elastic optical network(EON), a service label protection algorithm based on bandwidth and holding time is proposed. The algorithm marks the service from the two dimensions of service bandwidth and holding time. The services with larger bandwidth and smaller bandwidth are allocated to the frequency slots with smaller number and larger number respectively, and the services with longer holding time and shorter holding time are allocated to the frequency slots at both ends of spectrum and in the middle of spectrum respectively. Simulation results show that compared with the traditional algorithm, this algorithm can effectively reduce the blocking probability of EON and improve the reliability of the network.

In order to meet the needs of ultra-large capacity data transmission between ultra-big data centers, the researchers develop a coating diameter of 200 μm optical cable with 6912 cores. The structure and performance of 200 μm optical fiber and the key technologies of spider web fiber ribbon structure, optical fiber identification and left and right(SZ) stranding are introduced. After mechanical and environmental performance tests, the result show that the performance of optical cable with 6912 cores meets the requirements of optical cable standard and practical applicable.

In order to improve the transmission capacity of the optical fiber communication system, the photonic crystal few-mode fiber is optimized by full vector finite element method. The light field distribution and effective mode field area of stimulated Brillouin scattering(SBS) in the photonic crystal few-mode fiber are calculated, and the influences of pump power on slow light time delay and pulse broadening factor are also simulated. The results show that the SBS threshold decreases with the increase of fiber effective length; Under the same conditions, the SBS threshold of LP01 mode is less than that of LP11 mode, but the slow light time delay of LP01 mode is greater than that of LP11 mode; The slow light time delay and broadening factor of the two modes increase linearly with the increase of the input pump power. Optimizes the input pump power can be obtained that slow light time delay of LP01 mode and LP11 mode are respectively 881 ns and 533 ns, meanwhile the corresponding broadening factors are 1.453 and 1.293 separately.

In order to solve the problem of unstable working state of silicon-based microring devices caused by thermal effect, this paper proposes a real-time stability control technology for large-scale photonic integrated circuits based on microring resonator array low-speed orthogonal perturbation signals. It is verified that the scheme can effectively extract different channel state information through a single detection channel by buliding the numerical simulation model, and an orthogonal demodulation system is built for experimental verification. Simulation and experimental results show that the scheme can realize the stable control of large-scale photonic system.

In order to effectively realize packet transmission network(PTN) time synchronization, this paper introduces the synchronization principle of 1588v2 protocol, analyzes the key technology of PTN realizing high-precision synchronization, proposes a phase compensation algorithm of network slave clock, and carries out the PTN clock synchronization test based on 1588v2 protocol+ synchronous ethernet. The test results show that the PTN network clock synchronization based on 1588v2 protocol+synchronous ethernet and slave clock compensation algorithm not only realizes high-precision phase synchronization, but also effectively improves the slave clock phase stability.