Research On Carrier Recovery Technology In Coherent Optical Communication

Coherent optical intersatellite communication is one of the most attractive communication technologyin current satellite communication,which can increase the data rate,lower the power consumption,and meet the requirements of higher-capacity of data transmission in future.Basic properties of optical reception are reviewed in this paper.It is shown that the homodyne receiver modulated bybinary phase shift keying(BPSK)is themostsensitive method in optical detection.However,in order to achieve homodyne detection and provide a complex carrierrecovery system for local oscillator,we use anoptical phase-locked loop,then theory models are set up for few typical optical phase-locked loops,and comparison to their performance were made.We present an investigationof this costas-loop based carrier recovery system for opticalhigh-speed intersatellite data transmission,and combine thefundamentals of future optical intersatellite communication withanalyses of an optical phase-locked loop based carrier controlsystem,then set up theory models for the carrier controlsystem and the loop characteristics of the control system are analyzed.Besides,theimpact of noise is also discussed in this paper.In order to solve the problem that large error exists in initial frequency,thispaper improves the traditional costas phase locked loop structure,and put forward a new carrier recovery structure based on two feedback loop including PLL and FLL.For the coherent frequency deviation of optical BPSK receivers caused by laser temperature drift and Doppler frequency shift,we haveinvestigated a computationally efficient least-squares carrier frequency offset(CFO)estimation algorithm that utilizes the phase differencebetween samples with different time-domain separations,the CFO estimation error of the least-squares algorithm for 5-GBaud BPSK signal is less than 0.1 MHz.Compared with the algorithms based on phase difference between adjacentsamples,the proposed algorithm has obviously improved the estimated accuracy.At last,the system experiment is carried out andthe expectant experimental results are obtained via simulating the coherent reception system,detecting the entire loop signal,and design the hardware part.When the modulation rate is 5Gbps,the maximum phase error is 23 degree,and the detection sensitivity can reach-38 dBm.