Open AccessSingle-pixel optical modulation analyzer: a low-complexity frequency-dependent IQ imbalance monitor based on direct detection with phase retrieval
Author(s) -
Yuki Yoshida,
Setsuo Yoshida,
Shunri Oda,
Takeshi Hoshida,
Naokatsu Yamamoto,
Atsushi Kanno
Publication year - 2021
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.433148
Subject(s) - spectrum analyzer , baud , phase modulation , quadrature amplitude modulation , computer science , modulation (music) , optics , transmission (telecommunications) , signal (programming language) , frequency modulation , signal processing , electronic engineering , physics , phase noise , telecommunications , bandwidth (computing) , decoding methods , bit error rate , engineering , acoustics , radar , programming language
Tiny mismatches in timing, phase, and/or amplitude between in-phase (I) and quadrature (Q) tributaries in an electro-optic IQ modulator, namely IQ imbalance, can severely affect high baud-rate and/or high modulation-order signals in modern coherent optical communications systems. To maintain such analog impairment within the tight penalty limit over wavelength and temperature during the product lifetime, in-service in-field monitoring and calibration of the IQ imbalance, including its frequency dependence, become increasingly important. In this study, we propose a low-complexity IQ monitoring technique based on direct detection with phase retrieval called a single-pixel optical modulation analyzer (SP-OMA). By reconstructing the optical phase information lost during the detection process computationally via phase retrieval, SP-OMA facilitates the in-service in-field monitoring of the frequency-dependent imbalance profile without sending dedicated pilot tones and regardless of any receiver/monitor-side IQ imbalance. The feasibility of SP-OMA is demonstrated both numerically and experimentally with a 63.25-Gbaud 16QAM signal.