Nonlinearity Mitigation of PDM-16QAM Signals Using Multiple CSI-OPCs in Ultra-Long-Haul Transmission without Excess Penalty

Takeshi UMEKI
Takayuki KOBAYASHI
Akihide SANO
Takuya IKUTA
Masashi ABE
Takushi KAZAMA
Koji ENBUTSU
Ryoichi KASAHARA
Yutaka MIYAMOTO

Publication
IEICE TRANSACTIONS on Communications   Vol.E103-B    No.11    pp.1226-1232
Publication Date: 2020/11/01
Publicized: 2020/05/22
Online ISSN: 1745-1345
DOI: 10.1587/transcom.2019OBP0001
Type of Manuscript: Special Section PAPER (Joint Special Section on Opto-electronics and Communications for Future Optical Network)
Category: 
Keyword: 
optical signal processing techniques for optical communications,  optical phase conjugation,  nonlinear optics,  periodically poled LiNbO3 waveguide,  

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Summary: 
We developed a polarization-independent and reserved-band-less complementary spectral inverted optical phase conjugation (CSI-OPC) device using dual-band difference frequency generation based on highly efficient periodically poled LiNbO3 waveguide technologies. To examine the nonlinearity mitigation in a long-haul transmission using a large number of OPCs, we installed a CSI-OPC device in the middle of a pure silica core fiber-based recirculating loop transmission line with a length of 320km. First, we examined the fiber-input power tolerance after 5,120-km and 6,400-km transmission using 22.5-Gbaud PDM-16QAM 10-channel DWDM signals and found a Q-factor improvement of over 1.3dB along with enhanced power tolerance thanks to mitigating the fiber nonlinearity. We then demonstrated transmission distance extension using the CSI-OPC device. The use of multiple CSI-OPCs enables an obvious performance improvements attained by extending the transmission distance from 6,400km to 8,960km, which corresponds to applying the CSI-OPC device 28 times. Moreover, there was no Q-factor degradation for the link in a linear regime after applying the CSI-OPC device more than 16 times. These results demonstrate that the CSI-OPC device can improve the nonlinear tolerance of PDM-16QAM signals without an excess penalty.