The Design And Performance Analysis Of Loop Back Optical Fiber Communication System Based On Phase Modulation

With the increasing demand for communication capacity,optical fiber communication technology has been rapidly developed.Compared with the traditional on-off keying(OOK)modulation,the use of phase modulation and coherent receiver improves receiver sensitivity and system nonlinear tolerance.However,at the receive end,coherent reception,while having obvious performance advantages over conventional direct detection,is costly and is very unfavorable to cost-sensitive optical fiber communication systems.An important reason for the high cost of coherent receiving system is that a high quality laser is required as a local oscillator light source to perform coherent demodulation at the receiving end.Therefore,solving the cost problem of local oscillator light source is an important measure to solve the high system cost.Therefore,the study of a high receiver sensitivity,low cost optical fiber communication system,has important application value.Using phase modulation technology and coherent receiver,the sensitivity of the receiver can be better improved.The structure of the loop back system is used to make the source of the optical transmitter at the same time as the carrier light source and the local oscillator light source,which greatly reduces the system cost.The design and performance optimization of loop back optical fiber communication system based on phase modulation are studied in this paper.To be more specific,the research is carried out mainly from the following aspects:1.A loop back optical fiber communication system based on phase modulation is designed.The system structure can save cost and improve the sensitivity of the receiver,which is of great significance for the future application of the optical fiber communication system.2.The feasibility and basic performance of the loop back optical fiber communication system are verified by simulation.The feasibility of the system and the maximum transmission distance of the system are verified through experiments.In the case of normal communication,the system can achieve a maximum transmission distance of 20 km.3.Combined with the system principle and simulation analysis,and the problems encountered in the basic test experiments,an improved coherent demodulation scheme based on phase modulation for a loop back optical fiber communication system is proposed.By eliminating the optical power jitter,the polarization states of the two coherent optical branches are inconsistent,the optical power of the two coherent optical branches is too low,the Rayleigh backscattering noise and the delay of the two coherent optical branches cause the loop back optical fiber communication system getting a better demodulation results.