| In recent years,with the rapid development and maturity of computer,communication,sensor and integrated circuit technology,the application of laser power over fiber(PoF)longdistance transmission technology is becoming more and more widely.PoF technology has a series of advantages,such as anti electromagnetic interference,easy to realize high-voltage isolation,long-term operation and good reliability.Under some special working environment conditions,using PoF technology to power the sensor has obvious advantages.Using PoF technology to supply power to super high voltage power(SHVP)transmission line remote monitoring system is one of the typical cases.SHVP transmission line is an important part of China’s energy strategy of "west to East power transmission",and its operation is related to China’s energy security.On line real-time monitoring device is a necessary means to ensure the safe operation of SHVP transmission line equipment.The transmission distance of SHVP transmission line is up to thousands of kilometers or even more.It crosses no man’s land such as mountains,vast deserts and uninhabited water and grass along the line.The intelligent on-line real-time monitoring system of transmission line continuously monitors the working status of line temperature,humidity,wind speed,wind direction,leakage current,ice,video image and other sensors through a variety of sensors,These on-line monitoring sensors are mainly composed of electronic circuits,which must provide long-term and reliable power supply.Considering the installation position and ground insulation of these sensors,the power supply of electronic circuit can not be led out from the transmission line by wires.Therefore,how to supply power to the sensors in the on-line monitoring device is a key problem that must be solved in the practicability of the monitoring system.Many advantages of PoF system make it a good solution for power supply of remote monitoring system.However,PoF needs to inject higher laser power into optical fiber to supply power for power remote monitoring system and transmit longer distance through optical fiber.With the increase of laser power and transmission distance injected into optical fiber,the nonlinear effect of optical fiber has become the bottleneck factor restricting the application of PoF technology.In addition,the laser power density of high-power laser transmitted to the photoelectric conversion device through optical fiber is still very high,up to tens of kW/cm2 or even higher.Without special treatment or reasonable design,the conversion efficiency of photoelectric energy conversion materials will be reduced by using common photoelectric conversion devices(such as the optical power density of solar photovoltaic receiving is in the order of W/cm2),Saturation or even breakdown occurs.Therefore,the optical path of remote photoelectric energy conversion needs to be reasonably designed to meet the needs of remote photoelectric energy conversion materials under high optical power density injection.This paper has carried out detailed theoretical and Experimental Research on these problems.The research content can be summarized into the following four parts:the first part carries out the exploration and Research on the signal light and energy light transmission system of long-distance transmission of high-power laser fiber,and puts forward the technical scheme of laser energy and signal multiplexing suitable for the monitoring application of SHVP transmission line,The simplified theory of mode coupling of defective circular fiber is given,and the experimental test is carried out to verify the feasibility of the technical scheme of laser energy and signal multiplexing.In the second part,the transmission characteristics of Raman Stokes light in single-mode fiber are analyzed through theoretical analysis and simulation.According to the SRS theory and the principle of suppression of SRS effect by band stop filter,the method and evaluation criteria of suppression of SRS effect by fiber segmented band stop filter are proposed.The transmission spectra of multiple cascaded long-period gratings are analyzed,and the optimization algorithm is proposed to simulate and process the band stop filter,The corresponding experimental device is built to verify the proposed method and verify the effectiveness of the proposed method to suppress SRS effect.In the third part,the principle of photoelectric energy conversion is given,the wavelength conversion relationship and performance parameters of photoelectric materials are analyzed,and the laser energy conversion technical scheme under the condition of high optical power density is proposed.The material is selected as the main photoelectric conversion material,the InP semi insulating substrate with lattice matching is selected for epitaxial preparation,and the unit series is realized on the semi insulating substrate,The photoelectric conversion unit is arranged on the wall of the integrating sphere like spherical cavity,and the specially designed light guide cone is used to evenly scatter the high-power density laser transmitted by the optical fiber on the surface of the photoelectric conversion material,so as to solve the problems of saturation and breakdown.Adding thermoelectric materials to the outer wall of the spherical cavity for secondary conversion not only further improves the energy conversion efficiency,but also effectively alleviates the heat dissipation problem of the photoelectric conversion device.Entrust relevant parties to manufacture corresponding energy conversion modules,and carry out testing and technical verification.At 1550 nm,when the input laser power is 80 mW,the photoelectric conversion efficiency is more than 25.4%.In the fourth part,based on the breakthrough of the main key technologies of optical fiber nonlinear effect suppression and efficient photoelectric conversion,the system is builded,the performance of the system is tested,evaluated and analyzed.In the 1550nm band,the injected single-mode fiber laser power is 10W.After 103km single-mode fiber transmission,the output laser power is 87mw.After conversion by the photoelectric conversion device,26mW electric energy is obtained,which can drive the monitoring circuit with working voltage of 2.5V to work normally,and the expected design effect is achieved. |
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