High Precision OTDR System Design In Onboard Network

Modern communication network includes microwave communication,optical fiber communication and satellite communication.Optical fiber has the advantages of low loss,wide transmission band,large transmission capacity and anti-electromagnetic interference,that’s why optical fiber communication has gradually become the main mode of modern information transmission.The onboard avionics data bus based on optical fiber communication has gradually replaced the traditional data bus with copper or aluminum core as the transmission medium.Compared with common fiber networks,onboard avionics optical networks have shorter fiber threads and higher complexity.Therefore,high-precision optical fiber detection equipment is essential in the daily maintenance and detection of avionics optical network.OTDR based on time correlated single photon counting has the characteristics of non-destructive,simple structure and high sensitivity,which is very suitable for optical fiber detection of onboard avionics optical network.This artical focuses on the designation of high-precision OTDR system in airborne network,mainly studies the analysis of OTDR test curve,and realizes the location of optical fiber fault and the location of optical fiber end.The main work of this artical is as follows:1.According to the optical fiber detection accuracy requirements in onboard avionics network and OTDR principle,a high-precision OTDR system scheme based on time correlated single photon counting technology was designed.2.I analyze the principle of wavelet transform and improve the signal-to-noise ratio of OTDR test signals by threshold denoising method.According to the spatial local property of wavelet transform,which can describe the feature of signal details,an adaptive window location method is proposed.MATLAB simulation experiment verifies that this method can accurately locate the fiber fault position and fiber end position.3.According to the software design requirements of high-precision OTDR system in onboard avionics network,worked out the software design scheme.By means of mixed programming of Qt and MATLAB,the software programming of high-precision OTDR system in airborne network is completed.4.When the incident light pulse width is 1ns,the detection time is 6000 ms,and the sampling resolution is 0.1ns,the test environment is built to complete the test and analysis of the high-precision OTDR system.System performance test results show that the dynamic range of the high-precision OTDR is greater than 20 dB,the distance resolution is less than 0.1m,the event blind area is less than 0.1m,and the attenuation blind area is less than 0.2m,which fully meets the performance requirements of airborne avionics optical network for optical fiber detection instruments.The event points in the event detection results realized according to the optical fiber detection data are consistent with the actual optical fiber faults,and the accuracy of about ?3cm exists between the length of the optical fiber and the position of the event points and the actual optical fiber position.