The Model Of Bit Error Rate For Laser Communication Based On Superconducting Nanowire Single Photon Detector

Superconducting nanowire single photon detector(SNSPD)has the advantages of high sensitivity,low noise and high detection speed,SNSPD had been used in the field of space laser communication,obtaining the latest application and achieving the breakthrough results.In this paper,we introduced the working principle and development process of SNSPD,demonstrates its superior performance and development potential,and we introduced in detail the SNSPD used in deep space laser communication-the Lunar Laser Communication Demonstration.On the basis of the characterization of traditional device performance,we tested device of special function:for a kind of photon number resolution device with parallel resistance,we extracted 6 kinds of amplitude of the output pulse shape,also observed the influence of counter voltage identify to count rates,all proved that the device has 6 photon resolution;for the polarization insensitivity device with high refractive index material Si,we used a wide band light source and a polarization controller,resulted that the effect of polarization on device efficiency was greatly suppressed,the efficiency of parallel polarization was 61%and the vertical polarization was 56%at 1550 nm,The experimental results and simulation results were consistent.laser communication at single photon level needs not only to consider the effect of transmission environment,also the performance of used single photon detector and the photon number distribution.In this paper,we introduced system detection efficiency and dark count rate of SNSPD based on the photoelectric detecting model without considering the effect of atmospheric turbulence,established the mathematical model of bit error,and put forward the formula of system bit error rate.Need to emphasize that the bit error rate is an important parameter to measure the performance of laser communication system.As a result,the calculation of bit error rate includes the whole process of photoelectric conversion.In order to analyze how to affect the size of system bit error rate,we simulated two factors of the formula,light intensity and laser pulse repetition frequency first.The results showed that light intensity has the greatest impact on error bit rate.With the light intensity increases from 0.01 to 1000 photon/pulse,error bit rate significantly decreases from 10^-1 to 10^-7 level.The influence of laser pulse repetition frequency is restricted by different light intensity,that is on the decline with the increase of pulse repetition frequency.Then we measured the error bit rate through experiments,which validated the simulation model.However,when increasing light intensity or speed,experimental BER of about 10^-4 orders of magnitude is higher than simulation,the reason may be that the insufficient of actual communication modulation extinction ratio of optical signal and the background noise through optical fiber increase the dark count rates.The above model and experimental results could be the foundation of high-speed deep space laser communication such as moon-earth and Mars-earth based on SNSPD.