Multi-dimensional multiplexed optical network is the development direction of transmission backbone network, and it promotes the development of network technologies. This paper analyses the key technologies of multi-dimensional multiplexed optical network by investigating the development needs of the information communication network, introduces the research status on space division multiplexing technology at physical transmission level, and explains cutting-edge technologies with typical significance in the architecture, spectrum allocation and spectrum reconstruction of multi-dimensional multiplexed optical networks. Finally, the development direction of multi-dimensional multiplexed optical network and its cutting-edge technology are prospected.

Aiming at the problem of narrow dynamic range when microring resonators are used for refractive index sensing, this paper proposes a refractive index sensing technology based on few-mode silicon nitride micro-ring resonators, which enables the calculation of resonance wavelength drift without considering the original reference value and increase the refractive index detection range, and verify that higher-order modes are more sensitive to environmental changes. After theoretical analysis, a simulation model is established to verify the feasibility of the method, and the sensing experiment is carried out with the solution to be tested with different refractive index. Finally, the refractive index sensitivity of 91.79 nm/RIU and the resolution of 10-5 RIU are obtained.

General sensors have high sensitivity, but they are bulky and not easy to package. Fabry-Perot(F-P) cavity type sensor has been widely concerned for its simple structure, small size and easy packaging. An F-P cavity refractive index sensor is formed by fusing two different refractive index optical fibers and immersing the sensing fiber cladding in the liquid to be measured. The minimum resolution of the sensor is 3.0135×10-4, the length of sensing optical fiber is only 15 μm, the size is far smaller than other F-P cavity interferometers, and the accuracy of the length of sensing optical fiber is very low, so it is easy to manufacture.

In order to study the change of average transmitting power of pulse signal in different order of pulse position modulation(PPM) at the transmitter end in optical communications, this paper uses a two-stage amplification system based on the theoretical analysis model of Yb-doped fiber amplifiers. By optimizing the length of gain fiber, the average output power characteristics of optical emission system with different modulation orders are simulated. The simulation results show that under the limitation of pump power, the optimal gain fiber length under different modulation orders will be affected by the pump power. As the modulation order increases, the optimal gain fiber length also increases, but it has little effect on the average output power; when the hardware conditions of the fixed optical transmission system are unchanged, the average output power of the signals at different modulation orders is not equal, the average transmission power of 128PPM is only about 51% of 4PPM, and the transmission power loss is nearly 3 dB.

Aiming at the problem of wasting high-efficiency wavelength bands in the common aperture polarization multiplexing space laser communication optical antennas using beam splitter, a beam splitting structure is designed by using polarizing beam splitting prism and Faraday rotator. According to the parameters of the existing space laser communication device, the requirements for the isolation of beam splitting structure in space laser communication system are analyzed, the isolation and optical loss of the structure are calculated, and the applicable ranges are analyzed. The calculation results show that the structure can be applied to common-aperture polarization multiplexing space laser communication optical system.

In order to explore the effect of atmospheric turbulence on deep-space laser communication, the Gamma-Gamma distributed atmospheric channel model and means to suppress atmospheric turbulence are theoretically discussed. A deep space laser system model based on array transceiver is introduced, and the system's bit error rate under different turbulence conditions is simulated. The results show that when the signal-to-noise ratio is 20 dB, the downlink communication bit error rate under weak turbulence is 4 orders of magnitude lower than that under strong turbulence. When the intensity of atmospheric turbulence increases, the bit error rate of the system increases. At the same turbulence intensity, the influence of atmospheric turbulence on uplink communication performance is greater than that on downlink.

In order to study the influence of light intensity flicker on the visible light communication of light emitting diode (LED), based on the spatially incoherent monochromatic LED light source, the channel transmission characteristics of visible light communication under weak turbulence are theoretically studied, and the closed expression of light intensity scintillation coefficient of monochromatic LED visible light communication system is deduced. The system characteristics of LED and laser visible light communication under different factors are compared and analyzed. The simulation results show that the scintillation coefficient of LED visible light communication is smaller than that of laser visible light communication under weak turbulence, and the system bit error rate caused by turbulence disturbance is also lower. In addition, with the increase of light intensity flicker coefficient and average transmitted light power, the bit error rate gap between LED and laser visible light communication systems affected by turbulence is gradually increased.

In order to improve the simulation accuracy on the phase screen of dynamic atmospheric turbulence simulation, a method for measuring time correlation using time covariance is proposed. Research has been carried out on atmospheric turbulence phase screen simulation methods based on liquid crystal spatial light modulators(LC-SLM), time characteristics, etc. The power spectrum inversion method is used to generate a turbulence simulation phase screen, and then the calculation method of the time variable and time power spectrum is given. Finally, an atmospheric turbulence phase screen simulation experiment system based on LC-SLM is established, and the above method is verified experimentally. The experimental results show that in the case of laser distortion loss, the calculation error of the time covariance can be controlled to about 8.0％, and the time simulation accuracy of the phase screen is better under this simulation method.

The power supply and distribution capability of remote power supply system, directly affects the development and construction of the marine integrated information optical network. The structure of remote power supply network and high power shore-based power feeding and high power supply changeover submarine unit, are the keys that need to be solved. According to the marine integrated information optical network with different application characteristics, the corresponding remote power supply system scheme and power budget method are proposed by theoretical analysis of the network structure and application environment, and the realization scheme of shore-based power feeding equipment (shore station high power output) and sub-marine unit (high power conversion of underwater power supply) is given. Finally, the development direction of remote power supply technology for marine integrated information optical network is pointed out.

In order to satisfy the demand of secure communication, a scheme of dual-channel chaos communication based on three semiconductor ring lasers(SRL)is proposed. The time series, autocorrelation diagrams and eye diagrams under different conditions are given through numerical simulation, and the influence of transmission distance on communication quality is also discussed. The research show that the quality of chaos signal is poor for the drive SRL(D-SRL) subjected to self-feedback, after introducing mutualfeedback, the quality of chaos is significantly improved. As the transmission distance increases, the quality factor to quantify the quality of secure communication gradually decreases, but when the distance increases to 130 km, the quality factor remains above six. This scheme enables long-distance dual-channel secure communication.

Supercontinuum(SC) light sources with high powers and broad spectra are widely employed in the fields of spectroscopy and biomedicine. Several schemes for high power supercontinuum generation based on the passive and active fibers are introduced, various schemes are compared in the aspects of fiber materials, bandwidth, and output power. In this paper, it is pointed out that the reasonable selection of fiber type or structure is conducive to the improvement of SC bandwidth and output power.

In order to increase core rod size and maintain the ideal deposition efficiency and qualified optical parameters, this paper studies the main factors affecting the core rod size by vapor phase axial deposition method. The number of deposition blowtorch, the flow rate of SiCl4 and the lifting rate of soot body are optimized. In the deposition process of three blowtorches, when the flow rate of SiCl4 in the first and second clad blowtorch is increased to 4.0 slm and 5.0 slm, and the lifting rate is reduced to 85 mm/h, the experimental results show that the deposition rate increases to 15.8 g/min, the bulk density of soot body increases to 0.319 g/cm3, the core rod size increases to 99.1 mm, and the deposition efficiency reaches 52.2%, and the refractive index profile of G.652D single-mode fiber is maintained.

In order to obtain a short-length polarizing beam splitter with a high extinction ratio, a hexagonal dual-core photonic crystal fiber(PCF) polarizing beam splitter based on SiO2 is designed. The polarizing beam splitting is performed using the full vector finite element method and mode coupling theory. The coupling length, coupling length ratio, extinction ratio and bandwidth of the filter were numerically analyzed. The research results show that at a wavelength of 1.55 μm, the length of the polarization beam splitter is 103.05 μm, the extinction ratio is as high as 117.78 dB, and the bandwidth of the extinction ratio is greater than 20 dB is 100 nm, covering the entire C-band and most of the S and L bands.

Parameter intunability in microwave photonic filter(MPF) limits its application in all-optical networks. A multi-parameter tunable design of a multi-channel MPF by utilizing the structural characteristics of the periodic array of a sampled fiber Bragg grating(FBG) is proposed, using optical mode coupling theory and matrix determinant to analyze the spectrum characteristics of the sampled FBG. The simulation model of multi-channel MPF based on fourth-order sampling FBG array is established, and the simulation results show that the channel bandwidth of MPF can be increased by increasing the refractive index change rate; the channel interval of MPF can be increased by increasing the optical path difference of adjacent FBG; the center wavelength of MPF can be tuned by adjusting the temperature of FBG, so that MPF can swich flexibly between low-pass, high-pass, band-pass and band-stop filters.