In order to solve the problems of low sensitivity and easy oxidation of metal film in the photonic crystal fiber(PCF)temperature sensor, a double coating with side polishing PCF temperature sensor based on surface plasmon resonance(SPR) is proposed in this paper. Two polished surfaces of the PCF are perpendicular to each other, the polished surface of the fiber are coated with silver, and a layer of SiO2 film with a thickness of 20 nm is coated outside the silver film. All numerical simulations of sensor characteristics are performed in the COMSOL software. The simulation results show that the PCF temperature sensor has a temperature measurement range of 10~60 ℃, a highest sensitivity of 20.2 nm/℃, and a temperature resolution of 4.95×10-3 ℃.

Fiber Bragg grating(FBG) is widely used in hydrogen measurement because of its fast response speed and quasi distributed measurement. In order to further expand the measurement range of hydrogen concentration, an FBG hydrogen sensor based on mesoporous platinum doped tungsten trioxide(Pt/WO3) powder is proposed, and an FBG sensor head is cascaded for temperature compensation. The experimental results show that when the concentration of hydrogen is increased from 0 to 32%, the maximum drift of the central wavelength of FBG is about 320 pm, the response time is about 10 s, and there is a good linear relationship in the range of 0-14% hydrogen concentration, the sensitivity is 11.69 pm/%H2, which can realize quasi distributed hydrogen concentration sensing.

In order to improve the accuracy of distributed optical fiber sensing system, the errors standard deviation of temperature and strain in multi parameter simultaneous measurement and single parameter measurement are compared theoretically. It is pointed out that under the typical configuration, the simultaneous measurement error standard deviation of double-fiber or double-wavelength method can reach 9 ~ 850 times that of single parameter measurement method, and the strain error standard deviation of double segment optical fiber method is 1.4 times that of single parameter measurement method. The fitting algorithm based on the pseudo-Voigt model is used to extract the Brillouin frequency shift. The calculation results validate the above conclusions.

In order to explore the influence of different outer coatings on sensing performance, a photonic crystal fiber (PCF)refractive index sensing structure based on surface plasmon resonance(SPR) is designed in this paper, the outer surface of the optical fiber is coated with a metal film. Through finite element method, the effects of coating materials are gold, silver, graphene and silver+zinc oxideon the sensing performance have been compared. Numerical studies show that when the structural parameters are the same, in the refractive index range of 1.33~1.38, the sensitivity of the sensing structure with graphene as coating material is higher, up to 7000 nm/RIU, gold as coating material is 5000 nm/RIU, silver and silver + ZnO as coating material are both 4000 nm/RIU; In terms of sensitivity fitting linearity, each coating has high linearity, and the linearity of silver coating is the highest, which can reach 0.99112.

The application of network coding (NC) in passive optical network (PON) can better solve the problem of bandwidth requirement. A dynamic wavelength and bandwidth allocation (DWBA) algorithm based on NC is proposed for time and wavelength division multiplexing passive optical network(TWDM-PON). The algorithm comprehensively considers the round trip time(RTT) of optical network unit(ONU), the bandwidth requirements of coded ONU group and the queuing delay after the introduction of NC, dynamically adjusts the scheduling order of coded ONU group, selects multiple wavelengths according to the sequence of upload time, and uploads the data packets of coded ONU group as soon as possible. The simulation results show that the proposed algorithm can reduce queueing delay and end-to-end delay and improve network throughput.

In order to improve the flexibility and availability of information transmission in the software defined packet transport network(SPTN), a centralized control software defined network(SDN) controller is introduced as the core of the SPTN under the framework of the SDN to realize the separation of control and forwarding. This paper studies the cluster deployment in SPTN by using the Raft algorithm to make multiple controllers work together to solve the reliability and scalability problems of a single controller node. The SDN controller cluster uses the ETCD database to realize the functions of Raft algorithm election, controller master/backup switching, data synchronization and persistence. The experimental results show that the Raft algorithm can be used normally in the SDN controller cluster, and its performance has been improved in terms of convenient network service opening, flexibility and reliability of network information transmission.

In order to realize high-precision time-frequency signal transmission more flexibly and conveniently, spatial link is used to replace optical fiber for proceed time-frequency transmission. This paper describes the basic principle of frequency transmission of free space optical frequency comb. In the experiment, the femtosecond optical frequency comb locked to the rubidium atomic clock is sent to the far end through a 102 m free space link, which is detected directly by a high-speed detector, and the optical frequency comb repetition data are collected by a high-precision frequency counter. The experimental results show that the system is finally realized the jitter scope of the 100 MHz repetition signal at the receiver is 3.5 mHz in 30 min, and the repetition frequency stability is 4.26×10-12/s、4.81×10-13/100 s.

Aiming at the problems of narrow beam, small divergence angle, blocked output power and difficult alignment of laser diode(LD) light source, a deep sea high-speed wireless optical communication system based on commercial blue light emitting diode(LED) is proposed, and the system is tested and simulated in a kind of seawater channel of 10 m and 50 m respectively. The experimental and simulation results show that, in order to ensure the bit error rate of the system is less than 10-3, when the underwater channel is 10 m long, the data transmission rate can reach 500 Mb/s, and when the underwater channel is 50 m long, the data transmission rate can reach 20 Mb/s.

Aiming at the generation mode of quantum entanglement, three kinds of common preparation methods of quantum entanglement sources are introduced emphatically, including the preparation of quantum entanglement sources based on spontaneous parametric down conversion(SPDC), four wave mixing(FWM) effect and quantum dot. The principle, advantages, disadvantages and quality indexes of quantum entanglement source are analyzed respectively. Finally, the research and application direction of preparation methods of quantum entanglement source are prospected.

In order to meet the increasing bandwidth demand of users in the future, starting from the key technology of physical layer of high-capacity optical access network, this paper summarizes the standardization status of the next generation passive optical network(NG-PON), reviews the advanced modulation formats in the physical layer, the enhanced power budget technology, the physical layer impairment and suppression based on the advanced digital signal processing(DSP) algorithms. In addition, the future reseach directions of NG-PON physical layer is prospected.

In order to improve the performance of quantum dots fiber amplifiers, a strategy of compositing PbS quantum dots and mesoporous silica is proposed to increase the content of quantum dots on the tapered region of the fiber. The PbS quantum dots with oleic acid ligands loaded into the aminated mesoporous silica(NH2-MSN) through a single electron of nitrogen, and the quantum dots are enriched on NH2-MSN. NH2-MSN is connected to the hydroxylated optical fiber through hydrogen bond, so the density of PbS quantum dots on the tapered is greatly improved. The experimental results showed the on/off gain of the amplifier increased from 1.1 dB to 8.09 dB at 1550 nm with pump power increasing from 50 mW to 300 mW. The on/off gain finally saturated when the pump power is 280 mW.