Noise performance of optical fiber transmission links that use non-degenerate cascaded phase-sensitive amplifiers

Abstract

Based on semi-classical theory, the noise performance of a multi-span fiber optical transmission system employing a cascaded phase-insensitive amplifier (PIA) and phase-sensitive amplifiers (PSAs) is investigated. Compared with the pure-PIA and pure-PSA based in-line amplification schemes, the copier + PSA scheme is found to improve the system NF by up to 6 and 3 dB, respectively, in an optimized long-haul fiber link. In addition, this cascaded configuration will significantly relax the requirement for accurate phase- and wavelength-locking which is rigorously needed in the pure-PSA configuration. This scheme is also modulation-format independent. As a proof of concept, the NF of a fiber parametric amplifier based copier + PSA cascade with inter-stage attenuation representing the fiber link is measured, which shows a 1.8-dB total NF improvement over the conventional EDFA cascade.

Injection locking-based pump recovery for phase-sensitive amplified links

“…The copier-PSA scheme has been thoroughly investigated and it has been shown theoretically that a transmission link implementation of the scheme can give up to 6 dB link NF improvement over conventional PIA-based schemes and a 3 dB improvement over all PSA-based schemes [13,14]. This has also been shown experimentally for a copier-loss-PSA system, where the link was emulated by a lumped signal/idler loss [5].…”

Optical Injection-Locking-Based Pump Recovery for Phase-Sensitively Amplified Links

“…2(a) also shows that there is a 4.2 dB sensitivity difference between the PSA case and PIA case. Considering the theoretical 6 dB lower NF for a PSA amplified system compared to a PIA amplified system [2] difference may be expected to be higher. However, the difference is the same both with and without IL indicating that there is no significant penalty caused by the IL process itself.…”

“…After idler generation in the copier, the lossy optical link serves to de-correlate noise on the signal and idler waves [2]. The mid-stage is used for both control of the relative phases, polarizations and amplitudes of the pump, signal, and idler waves and also for recovery of the pump power loss.…”

“…By inserting a lossy link between the copier and the PSA, it has been shown theoretically [2] and experimentally [3] that up to a 6 dB noise figure (NF) improvement can be obtained compared to conventional PIA-based amplification schemes, e.g. an erbium-doped fiber amplifier (EDFA)-based scheme.…”

Phase-Sensitive Amplifiers for Optical Links

“…The concept described above can also be extended to multi-span DWDM links, with PSAs as in-line amplifiers [12], also providing up to 6 dB link NF benefit over a PI amplifier-only link. …”