Aiming at the influence of indoor complex environment and indoor lighting node topology on visible light positioning accuracy, a visible light indoor positioning method for multi-LED lighting nodes is designed based on the approximate perfect triangle point test(APIT) algorithm. The method uses the signal transmission time as the judgment voucher of the node spacing size, and combines the APIT positioning algorithm to realize indoor visible light localization. The simulation results show that the positioning error of the positioning method fluctuates around 0.24 m. On the basis of ensuring the positioning accuracy, the layout cost of the positioning device is simplified and the computational efficiency of the positioning algorithm is improved at the same time. The above aspects of improvement make the application of the system more stable and applicable in practical scenarios.

In space optical communication, both communication terminals need to detect the deviation of the incident optical axis to ensure that the communication link is unblocked. However, the beacon light used by the optical antenna control system has a large loss after long-distance transmission, and is strongly disturbed by background light and dark current noise. So, the accuracy of spot detection of the four-quadrant detector(QD) is reduced. To solve this problem, according to QD operating characteristics and noise characteristics, a new method based on amplitude modulation and cyclic cross-correlation is proposed. Under the condition of low output signal to noise ratio(SNR) of QD, this method can accurately measure the photocurrent amplitude of each quadrant of QD and calculate the accurate spot position. Experiments results show that, when the output SNR of QD is -14.58 dB, the absolute error of this method is less than 0.012 mm, the effectiveness of the method is proved.

To overcome the disadvantage of low demodulation accuracy of reflective spectrum of fiber Bragg grating sampled by portable demodulator, a wavelet transform-based Gaussian(WTG) curve fitting method is introduced. The reflection spectrum signal is decomposed by wavelet transform, and the wavelet detail component is quantized by threshold. On this basis, the signal is reconstructed by the processed detail component and approximate component. Then, the reconstructed signal is interpolated to fit the Gauss curve, and the Levenberg-Marquardt(LM) algorithm is used to optimize the Gauss fitting coefficient. The simulation results show that the WTG algorithm has the smallest peak positioning error and higher demodulation accuracy compared with the direct peak seeking algorithm and the Gauss fitting algorithm.

In order to overcome the bottleneck of electric mixer and achieve wide bandwidth signal mixing, a microwave photonic mixing scheme based on dual polarization double parallel Mach-Zehnder modulator is proposed. Carrier suppression single sideband modulation is achieved by adjusting six direct-currentbias voltages. Radio frequency(RF) and Local oscillator(LO) signals are injected into modulators separately, separated from each other and modulated separately. They are transmitted on two orthogonal polarization states. Finally, both of them are adjusted to the same polarization state by polarization controller and polarizerto beat the frequency. The switching of up-conversion and down-conversion only needs to change one of the direct-current bias voltages. The simulation and experiment results show that the scheme is feasible. When the RF frequency ranges from 11 GHz to 25 GHz, the RF spurious rejection ratio of the up-converted or down-converted signals output by the scheme is no less than 25 dB, and the spectrum purity is high and the tunability is good. The switching between the frequency conversion modes is convenient, the RF/LO isolation of the system reaches -49 dB.

With the electromagnetic environment of the modern battlefield being increasingly complicated and the interleaving between different frequency and format radio frequency(RF) signals in intelligence reconnaissance, electronic countermeasures, communication and remote sensing systems, the wide bandwidth, anti-interference, and low losses superiority of the RF signal optical fiber transmission technology will play a key role in these systems. This paper reviews the characteristic and advantage of the RF signal optical fiber transmission technology, introduces the research status, development situation at home and abroad, and makes a vista of the RF signal optical fiber transmission technology.

The line side module CFP2-DCO has important and extensive application in 4G/5G network construct. Optical signal-to-noise ratio (OSNR) is an important parameter to evaluate the performance of the CFP2-DCO. The interference of polarization mode dispersion(PMD) and chromatic dispersion (CD) had important influence on the OSNR performance, the degradation of the OSNR induced by the PMD and CD is the OSNR penalty of PMD and CD. Different kinds of OSNR measurement methods are discussed. An automatic measurement platform on OSNR and PMD/CD penalty of the CFP2-DCO is introduced for the lab test requirement of communication equipment manufacturer. The OSNR and the PMD/CD penalty of the CFP2-DCO is tested using this platform. The PMD/CD penalty on the OSNR and the PMD/CD versus OSNR relation curve is further measured. The test results show that the OSNR requirement of the telecommunication system will be increased with the PMD/CD interference increasing. So, the PMD/CD interference should be decreased to optimize the system performance.

To study the influence of different materials on Fabry–Perot(F-P) interference acoustic sensor. An extrinsic F-P acoustic sensor based on the structure of fiber end-membrane was fabricated with several different metal diaphragm materials. Besides, the first-order natural frequency was obtained through simulating and analyzing the circular diaphragm using the method of finite element. Experimental results show that the sensor with gold diaphragm and zinc alloys diaphragm exhibit high sensitivity and good linear response property, and which can be detecting lower sound pressure.

In view of the current over 10 Gb/s high-speed SerDes interface of 8B/10B encoding requirement, this paper is based on the traditional multi-channel encoder and improves its structure. The polarity quick generation module is added and it reduces the waiting time of internal channel encoder. The efficiency of parallel encoding and data transmission rate are improved. Meanwhile, the output coding latency declines. The simulation results of the circuit show that the data transmission rate of the encoder reaches 20.6 Gb/s and 38.4 Gb/s respectively in the four-channel and eight-channel modes, and the coding output latency is one clock cycle, which fills the gap of the domestic low-delay high-speed 8B/10B encoder.

With the development of the internet, network data traffic is increasing rapidly, the concept of all-optical network (AON) is helpful to solve the problems of limited available bandwidth and low signal transmission rate. Among them, all-optical logic signal processing is an important part of AON. According to the principle of second order nonlinear effect of periodically poled lithium niobate(PPLN) waveguide, the output signal is successively sent to different PPLN waveguides for superposition processing, and the waveguide cascade structure of all-optical 2-4 line decoder is designed. The waveforms and eye diagrams are obtained by numerical calculation and simulation, and the full width half maximum (FWHM), peak power, delay time, extinction ratio of the output signal of all-optical 2-4 line decoder are analyzed. The results show that the logic function of 2-4 line decoder in optical domain is realized by cascading PPLN waveguides, and the transmission quality of optical signal is guaranteed, which provides a new device type for all-optical signal processing of PPLN waveguide.

Semiconductor core fiber has attracted more and more attention due to its special photoelectric characteristics. The drawing of the semiconductor core fiber is more complicated than the conventional silica fiber due to the difference in properties between the core and the cladding material. In this paper, the Ge-core fiber is taken as the research object, and the dynamic drawing process of the Ge-core fiber is simulated by the finite element method. The difference in flow rate between the core of germanium and the cladding of silica, and the effect of different fiber drawing speeds on this flow rate difference are studied. The simulation result shows that significant difference of the core and cladding flow rate is at the position of the neck-down region of the preform, and the different drawing speed has different effects on the flow rates of the Ge-core and the silica-cladding of the preform.

The low Raman gain of ordinary single mode fiber severely restricts the development of the Raman amplifier. Therefore, the development of high Raman gain fiber had important significance. This paper studied the Raman scattering enhancement properties of PbS-doped silica fiber. PbS-doped silica fiber and ordinary single mode fiber samples were prepared by modified chemical vapor deposition(MCVD) and their transmission loss spectra and Raman spectra were measured. The experimental results showed that the PbS-doped silica fiber had stronger Raman scattering intensity. Under different pump power conditions, Raman amplification experiments were carried out. Compared with the ordinary single mode fiber, the PbS-doped silica fiber had larger Raman gain.

In order to increase the spectrum utilization in elastic optical networks(EON), an adaptive modulation and fragmentaware shared path protection algorithm is proposed. The proposed algorithm uses the spectrum block bearing weight (SBBW) to measure the ability of connection establishment for different spectrum blocks, and prefers the paths including links with larger SBBW as candidate working paths. The working path is established by choosing the spectrum block with the minimum difference of SBBW before and after the allocation. Then, the proposed algorithm selects the paths containing links with larger weight of both available spectrum block and protection spectrum block as candidate protection paths. The proposed algorithm prefers to use the protection spectrum block with the smallest SBBW difference before and after the allocation to establish the protection path. When the establishment fails, the available spectrum blocks with the minimum difference of SBBW before and after the allocation are selected to establish the protection path. Simulation results show that the proposed algorithm can reduce the bandwidth blocking probability, spectrum fragmentation ratio and spare capacity redundancy.

Quantum key distribution protocol can provide an unconditional secure key for two communication parties. This paper proposes a quantum key distribution protocol based on squeezed source without monitoring signal disturbance. The quantum key distribution is realized by cyclic shifting the quantum signal at the receiver and measuring the phase difference of any two quantum signals. This protocol can not only generate a secure key, but also do not need to monitor the signal disturbance so as to reduce the complexity of implementation. Moreover, a two-intensity decoy states method is applied into the proposed protocol to estimate the key rate. The experiment results show that both the maximum transmission distance and the security key rate of the proposed protocol is significantly improved. Moreover, only two-intensity decoy state is necessary for approaching the asymptotic limit with infinite decoy states in the proposed protocol.