Journal
OPTICS EXPRESS
Volume 29, Issue 20, Pages 31115-31129Publisher
OPTICAL SOC AMER
DOI: 10.1364/OE.433148
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Funding
- Japan Society for the Promotion of Science [JP19K04384]
- National Institute of Information and Communications Technology [205]
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Small mismatches between in-phase and quadrature tributaries in an electro-optic IQ modulator, known as IQ imbalance, can greatly impact high baud-rate and/or high modulation-order signals in coherent optical communications systems. In this study, a low-complexity IQ monitoring technique based on direct detection with phase retrieval, called SP-OMA, is proposed for in-service in-field monitoring of frequency-dependent imbalance profile without requiring dedicated pilot tones or being affected by receiver/monitor-side IQ imbalance. The feasibility of SP-OMA is demonstrated both numerically and experimentally with a 63.25-Gbaud 16QAM signal.
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. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
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