Analysis of BPSK homodyne receivers based on modified balanced optical phase-locked loop in the presence of non-negligible loop propagation delay

Abstract

Optical homodyne receivers based on modified balanced optical phase-locked loop is analyzed taking into account loop propagation delay. This modified loop contains all the components of a standard BOPLL in conjunction of an additional phase modulator. This modified loop offers a much improved tracking performance and also shows good improvements in the reduction performance over previously reported methods, like, relaxed line-width requirement and improved lock-in range. This study for the first time shows the imperfect-phase-recovery-induced power penalty as a function of laser line-width with the optimum phase deviations in the presence of non-negligible loop propagation delay. It is found that in order to maintain a 10−10 BER system performance with ξ=1, R=1A/W, PR=−53dBm, Δυ=1MHz, phase modulator sensitivity KPM=10rad/V and 10° phase deviation between the two transmitted bits, the loop delay must be kept below 3ns. Further, the required line-width with the non-negligible loop delay time is evaluated and found to be (2.1×10−3)/τ, where τ (s) is the loop delay. This number corresponds to BER=10−10, imperfect phase recovery power penalty of 1dB and phase modulator sensitivity KPM=20rad/V.