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Pilot-based cross-phase modulation compensation for coherent optical orthogonal frequency division multiplexing
1Department of Electrical and Computer Systems Engineering, Monash University, Wellington Road, Clayton, Victoria 3800, Australia.
Optics Letters
|May 5, 2011
Summary
A pilot-based nonlinearity compensator effectively mitigates cross-phase modulation (XPM) in optical systems. However, it does not compensate for self-phase modulation (SPM), requiring separate compensation for optimal signal quality.
Area of Science:
- Optical Communications
- Nonlinear Optics
Background:
- Coherent optical orthogonal frequency division multiplexing (CO-OFDM) systems are susceptible to nonlinear impairments like cross-phase modulation (XPM) and self-phase modulation (SPM).
- The Kerr effect in optical fibers causes intensity fluctuations to induce phase errors, degrading signal quality.
Purpose of the Study:
- To evaluate the effectiveness of a pilot-based nonlinearity compensator (PB-NLC) for mitigating XPM in CO-OFDM systems.
- To assess the impact of compensating for self-phase modulation (SPM) prior to PB-NLC application.
Main Methods:
- A pilot-based nonlinearity compensator (PB-NLC) utilizing unmodulated pilot tones within each OFDM channel was proposed.
- Phase errors caused by XPM were detected using pilot tones at the receiver.
- Self-phase modulation (SPM) was compensated using each channel's intensity waveform before XPM compensation.
Main Results:
- Numerical simulations demonstrated that PB-NLC effectively compensates for XPM.
- A 2.4 dB improvement in signal quality (Q) was achieved when SPM compensation preceded PB-NLC.
- Using PB-NLC without prior SPM compensation resulted in only a 0.9 dB improvement.
Conclusions:
- The PB-NLC is an effective method for mitigating XPM in CO-OFDM systems.
- The PB-NLC does not compensate for SPM, highlighting the need for a combined compensation strategy.
- Integrating SPM compensation before PB-NLC significantly enhances overall signal quality.
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