PPLN-Based Low-Noise In-Line Phase Sensitive Amplifier with Highly Sensitive Carrier-Recovery System

Koji ENBUTSU  Takeshi UMEKI  Osamu TADANAGA  Masaki ASOBE  Hirokazu TAKENOUCHI  

Publication
IEICE TRANSACTIONS on Communications   Vol.E99-B   No.8   pp.1727-1733
Publication Date: 2016/08/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.2015CCP0017
Type of Manuscript: Special Section PAPER (Special Section on Advanced Information and Communication Technologies and Services in Conjunction with Main Topics of APCC2015)
Category: Fiber-Optic Transmission for Communications
Keyword: 
phase sensitive amplifier,  periodically poled LiNbO3 waveguide,  

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Summary: 
We propose a highly sensitive carrier-recovery system for in-line amplification for binary phase shift keying (BPSK) signals in a periodically poled LiNbO3 based phase sensitive amplifier (PSA). We applied a discrete two-stage second harmonic generation/difference frequency generation (SHG/DFG) parametric conversion scheme to enhance the sensitivity of the carrier recovery. Owing to this two-stage SHG/DFG scheme, the conversion efficiency of the seed light for the injection locking needed for the pump generation can be improved compared to that of the cascaded SHG/DFG scheme. The new discrete scheme might also prevent the SNR degradation of the seed light caused by the ASE from the booster EDFA compared with the previous system that used the cascaded scheme. This novel carrier-recovery system exhibits high sensitivity with the SNR of over 7.8dB of the seed light, while tapped signal power is as low as -50dBm, which is low enough for injection locking. The new in-line PSA with this carrier-recovery system exhibits high gain of over 11dB. Since we successfully obtained the high gain property, we tried multistage amplification taking into account practical use and achieved it with both a high gain of 20dB and a noise figure that is almost as low as the standard quantum limit of a PSA.