In order to improve the adaptive matching ability of quantum security network to data flow and improve network quality of service(QoS) and user experience, a software-defined quantum security network(SDQSN) based on Markov decision process(MDP) security policy is proposed. SDQSN can adaptively select different quantum key management strategies with the change of network traffic, and rely on the real-time monitoring of quantum link, calculate network revenue based on MDP, and determine the security policy of the system, so that the system can flexibly switch between the security policies of quantum encryption and classic encryption, and maintain network security and ensuring network QoS benefits. The simulation results show that the SDQSN is more flexible and dynamic adjustable than the traditional quantum security network, which can effectively ensure the overall benefits of the network and enhance the user experience.

In quantum communication, channel noise will affect the reliability and effectiveness of information transmission. Two controllable quantum dialogue(CQD) protocols are designed, which can resist collective-dephasing noise and collective-rotation dialogue noise respectively. The comparative analysis shows that the protocol can not only avoid the impact of collective noise, but also avoid information leakage, and effectively reduce the online time of the controller, and can resist external and internal attacks.

Routing, modulation and spectrum allocation(RMSA) has become one of the main methods to improve the utilization of spectrum in elastic optical networks(EONs). Aiming at the routing of RMSA, a multi-hop routing, modulation and spectrum allocation(SDLN-MHRMSA) algorithm based on the shortest distance and the least nodes is proposed. The algorithm divides the path of the shortest distance and the least nodes into a certain number of sub optical paths through the optical electric optical converter with multi-hop routing, and then allocates the spectrum for the traffic request according to the distance adaptive modulation technology on each sub optical path. Theoretical analysis and simulation results show that the proposed algorithm has better performance in blocking rate and spectrum resource utilization than the traditional RMSA algorithm based on the shortest path.

Aiming at the optimization of signal-to-noise ratio of indoor visible light multi-user communication, an optimization algorithm based on genetic algorithm is proposed. By quantificationally analyzing the delay characteristics of each light emitting diode(LED) lamp signal emission path as the measurement value of gene contribution to signal-to-noise ratio, the maximum signal-to-noise ratio contribution retention and minimum signal-to-noise ratio contribution elimination methods are used to improve the crossover and mutation process of genetic algorithm. The simulation results reveal that for the LED selection problem, the proposed method converges faster and obtains better signal-to-noise ratio than the general evolutionary algorithm.

The future elastic optical network requires that the transmitter of the source node can dynamically change the modulation format and symbol rate of the transmission signal according to the transmission performance of the link and the diversified needs of users. A simplified two-stage intensity characteristic modulation scheme recognition algorithm is proposed. In this algorithm, quadrature phase shift keying(QPSK) signals are distinguished by Godard's error, and then 16 order quadrature amplitude modulation(16QAM) and 64QAM are further distinguished by intensity noise variance. The results show that when the minimum optical signal to noise ratio(OSNR) value of high-order modulation format signals such as physical data model-quadrature phase shift keying(PDM-QPSK), PDM-16QAM and PDM-64QAM is lower than 7% forward error correction(FEC) theoretical threshold(error rate is 3.8×10-3), 100% correct recognition rate can be achieved, and the number of symbols required by the proposed scheme is relatively small.

In order to meet the needs of ultra-high speed and ultra-long distance transmission in terrestrial long-distance trunk, researchers have developed G.654E optical fiber with ultra low loss and large effective area and small bending loss. Based on the requirements of the long-distance trunk system for optical fiber performance, the design and performance of refractive index distribution structure of G.654E fiber are discussed. The transmission experiment examples of 1234.2 km and 600 Gb/s on G.654E fiber are mainly introduced.

Aiming at the poor stability of output wavelength and power of some light sources in optical communication applications, a multi wavelength stable light source for optical transmission based on vertical cavity surface emission(VCSEL) is developed. The structure and working principle of the stable light source are described in detail. The central wavelength, output power and short-term and long-term stability of the output power are measured at 660 nm, 850 nm, 1310 nm, 1490 nm and 1550 nm respectively. The test results show that the stable light source has good performance and is suitable for optical communication transmission.

In view of the application requirements of broadband optical communication system for dense wavelength division light source, the shortcomings of single wavelength laser in dense wavelength division system are pointed out, and the principle and generation method of optical frequency comb light source are introduced. This paper presents a method of generating optical frequency comb based on phase modulation, and tests the generated optical frequency comb in broadband optical communication system, and verifies the application effect of optical frequency comb as multi-wavelength light source in broadband optical communication system.

In order to solve the problem of low tuning accuracy in wavelength switchable fiber laser, an erbium-doped fiber laser based on all fiber taper interference filter structure is proposed and designed. The fiber Mach-Zehnder(MZ) interference structure is fabricated by melting the multimode fiber with a fusion splicer. The periodic energy distribution is used to realize the wavelength flexibility of erbium-doped fiber laser tunable output. The experimental results show that the period of the fiber filter is 0.8 nm, the laser operating threshold is 58 mW, the single wavelength tunable laser output is realized in the L-band of 1573.45~1574.59 nm, and the minimum wavelength interval is 0.11 nm; the dual wavelength laser switchable output is realized by adjusting the polarization controller. In the 10 min stability test, there is no obvious wavelength drift.

When optical time domain reflectometer(OTDR) uses small pulse width test, its curve signal-to-noise ratio is low and dynamic is insufficient. If large pulse width test is used, the blind area will increase, which is not conducive to event point analysis. To solve this problem, the principle of two-sided filter is introduced, and the two-sided filter is introduced to filter the test data of OTDR. The experimental results show that the two-sided filter can improve the performance of OTDR products while increasing the dynamic range.

Aiming at the problems of low positioning accuracy, low sensitivity and high false alarm rate of distributed optical fiber vibration sensor in the market, this paper proposes a fiber optic micro vibration sensor based on double Mach-Zehnder(MZ) interference principle, and introduces the structure of the sensor, coherent detection technology and intrusion events pattern recognition technology. The experimental results show that the single trigger detection rate of the sensor is more than 99.7%, the multiple trigger detection rate is equal to 100%, and the single false alarm rate is less than 1%.

High-precision and high-stability time-frequency signal transmission is a reliable guarantee for the normal operation of on-orbit satellites. The transmission link bandwidth of time-frequency transmission system using redundant coding method is above Gb/s level. In this paper, a new time-frequency transmission system is designed, which optimizes the encoding and decoding methods with limited bandwidth, and achieves high-precision transmission of frequency standard signals under the bandwidth of 5 MHz link. The high precision transmission of time-frequency is realized by microwave photon fusion. The results showed that the time jitter of the time-frequency transmission system reached 1.65 ns and the frequency stability of 1.39×10-11/s and 3.45×10-12/(10 s).

The existing store and forward(SnF) scheduling methods suffer from high computational complexity and heavy state maintenance, which seriously restricts its application in the field of big data transfer. Moreover, the traditional global modeling results in a lot of redundant states in the scheduling problem. Aiming at this problem, this paper proposes a state fusion scheduling method based on time-shifting multi-layer graph(TS-MLG). The method reduces redundant states and improves the scheduling efficiency of the algorithm by fusing the states of preselected paths. The simulation results show that compared with the traditional scheduling method, the proposed method has the advantages of short computing time, good scheduling performance and less state maintenance, which suggests that it can provide real-time and efficient scheduling services for large-scale networks.

Aiming at the fluctuation problem of received power caused by atmospheric turbulence, an optical power equalization technology based on Erbium ion competition mechanism is studied. The influence of atmospheric turbulence on free space optical communication in the atmospheric channel model based on Gamma-Gamma distribution is discussed. The optical power equalization effect under different turbulence intensity is simulated. The simulation results show that the fluctuation range of received signal optical power can be reduced by more than 16 dB under the condition of medium intensity turbulence.