Abstract
This paper presents the quantitative measurement through an experimental test of 640 Gbps 16-QAM coherent-optical orthogonal frequency-division multiplexing (CO-OFDM) over 800 km optical fiber with mid-link optical phase conjugation (OPC) using highly nonlinear fiber (HNLF). The first focus is the OPC parameter optimization, including the optimization of HNLF length and signal/pump power that inputs into OPC. Four different HNLFs, as the illustrative examples, are investigated. The second focus is to investigate the effects of fiber dispersion, nonlinearity, and amplified spontaneous emission (ASE) noise on the long-haul transmission of 16-QAM CO-OFDM signal, and the OPC compensation efficiency. The performance evaluation focuses on the conversion efficiency (CE), received signal constellation, Q-factor improvement, and bit error rate (BER) at the receiver end. Such end-to-end performance evaluation is important because the 16-QAM CO-OFDM signal status is heterogeneous and the mitigation of transmission impairments to the signal is still unclear. The OPC parametric optimization is achieved experimentally using commercially available HNLFs with different scenarios and the numerical results are interpreted in conjunction with simulations.
Highlights
The optical network demands to have a transmission capacity of over 1000 Gbps, so coherent-optical orthogonal frequency-division multiplexing (CO-OFDM) as an advanced modulation scheme is currently under investigation to support both high spectral efficiency and long transmission distance
When 16-QAM CO-OFDM signal is given, the design of optical phase conjugation (OPC) involves the selection of highly nonlinear fiber (HNLF) length and the optimization of signal power and pump signal power that inputs into OPC, which are highly related to the characteristics of HNLF
This paper presents quantitative measurement through an experimental test of 640 Gbps 16-QAM CO-OFDM over 16 × 50 km optical fiber link with a mid-link OPC, which is implemented using FWM via HNLF
Summary
The optical network demands to have a transmission capacity of over 1000 Gbps, so coherent-optical orthogonal frequency-division multiplexing (CO-OFDM) as an advanced modulation scheme is currently under investigation to support both high spectral efficiency and long transmission distance. Dual-order Raman based mid-link OPC was tested in a 256 Gb/s dual-polarization 16-QAM transmission over 2 × 50.4 km single-mode fiber (SMF) [17], in which the performance evaluation in Q-factor achieved 7 dB reduction in nonlinear threshold and 5 dB optimum launch power, respectively. The investigation focuses on the effects of fiber dispersion, fiber nonlinearity, and ASE noise on the transmission of 16-QAM CO-OFDM signal and the compensation efficiency of using mid-link OPC with different HNLFs. The performance evaluation focuses on the transmission quality of 16-QAM CO-OFDM with mid-link OPC, including conversion efficiency, the received signal constellation, Q-factor gain, and BER at the receiver end. Equation (3) shows that the deterioration power of sensitive to HNLF length [2]
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