High-fidelity front-end response estimation and pre-compensation for bandwidth-limited coherent systems using...

Area of Science:

• Optical communications
• Signal processing
• High-fidelity system characterization

Background:

• Bandwidth-limited coherent optical systems face challenges in accurately estimating transceiver front-end responses.
• Conventional sequence-based probing methods can lose fine spectral details due to laser linewidth limitations.

Purpose of the Study:

• To propose a measurement-driven pre-compensation scheme using single-pulse (SP) probing for high-fidelity estimation of aggregate transceiver front-end response.
• To enable accurate characterization of spectral ripples under finite laser linewidth conditions.
• To improve performance in bandwidth-limited coherent optical systems.

Main Methods:

• Utilizing the temporal isolation of a single probe pulse for characterization.
• Employing numerical simulations to quantify phase-noise robustness.
• Conducting experiments with 60 Gbaud PDM-16QAM over a 300-km standard single-mode fiber (SSMF) link.

Main Results:

• The proposed SP probing scheme accurately characterizes fine spectral ripples, overcoming limitations of conventional methods.
• Numerical simulations show a normalized mean squared error (NMSE) of approximately -27 dB across a wide linewidth sweep (1 kHz to 100 MHz), significantly outperforming training-sequence-based methods.
• Experimental results demonstrate effective flattening of the estimated front-end frequency response, restoring matched-filter gain and improving launch power margin by 0.62 dB.

Conclusions:

• The single-pulse probing scheme offers a robust and high-fidelity method for transceiver front-end response estimation in coherent optical systems.
• This approach significantly enhances phase-noise robustness and improves system performance, including launch power margin.
• The proposed technique provides a valuable advancement for bandwidth-limited optical communication systems.