Larsson Rasmus, Vijayan Kovendhan, Schröder Jochen, Andrekson Peter A
Opt Express. 2023 Oct 23;31(22):36603-36614. doi: 10.1364/OE.499280.
The low noise figure of phase-sensitive amplifiers (PSAs) is attractive for optically pre-amplified measurement and communication systems. However, a major practical implementation difficulty pertains to the requirement of phase-locked signal, idler, and pump waves. Previously, injection locking to a co-propagating weak pump pilot or tapping portions of the received signal (lossy) for carrier re-generation have been used. Here we present a novel, lossless approach without any pump pilot, that generates a phase-locked receiver-local pump within the PSA using a digital dither-based optical phase-locked loop. We experimentally demonstrate a 2 dB noise figure with a low 0.3 dB penalty due to imperfect locking. By comparing the phase-locking performance in a PSA to that in a 50/50-coupler, we discuss and predict potential performance improvements connected to loop delay and laser phase characteristics.
相敏放大器（PSA）的低噪声系数对光预放大测量和通信系统具有吸引力。然而，一个主要的实际实现困难与锁相信号、闲频和泵浦波的要求有关。以前，已采用注入锁定到同向传播的弱泵浦导频或抽取接收信号的部分（有损耗）来进行载波再生。在此，我们提出一种新颖的、无任何泵浦导频的无损方法，该方法利用基于数字抖动的光学锁相环在PSA内生成一个锁相的接收机本地泵浦。我们通过实验证明了噪声系数为2 dB，由于锁定不完善导致的损耗低至0.3 dB。通过比较PSA中的锁相性能与50/50耦合器中的锁相性能，我们讨论并预测了与环路延迟和激光相位特性相关的潜在性能提升。
