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Probabilistically shaped coded modulation for IM/DD system.

Zonglong He, Tianwai Bo, Hoon Kim

|May 5, 2019

Summary

This summary is machine-generated.

Probabilistic constellation shaping (PCS) enhances optical communication by adapting symbol distribution to signal-to-noise ratio (SNR). This study efficiently applies PCS to intensity modulation/direct detection (IM/DD) systems, improving receiver sensitivity.

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Area of Science:

Optical Communications
Digital Signal Processing

Background:

Probabilistic Constellation Shaping (PCS) approaches Shannon capacity in coherent systems by adaptively adjusting symbol distribution to the signal-to-noise ratio (SNR).
Limited research exists on applying PCS technology to intensity modulation (IM)/direct detection (DD) systems.

Purpose of the Study:

To propose and demonstrate an efficient method for applying PCS technology to IM/DD systems.
To evaluate the performance gains of PCS in IM/DD systems compared to existing modulation techniques.

Main Methods:

Mapping forward error correction-encoded bits to pulse amplitude modulation (PAM) symbols by assigning uniformly distributed bits to the least significant bit of binary reflected Gray coding.
Implementing a pairwise symbol amplitude distribution where adjacent symbols share the same probability.
Evaluating performance via simulations measuring achievable rates and frame error ratios.
Conducting experimental demonstrations using a 10-Gbaud PAM-8 signal.

Main Results:

The proposed PCS scheme for IM/DD systems yields a negligible SNR penalty despite deviating from optimum distributions.
Simulations show the scheme provides a shaping gain superior to time-division hybrid modulation.
Experimental results demonstrate a 0.9 dB improvement in receiver sensitivity compared to uniformly distributed PAM-8 signals.

Conclusions:

The proposed PCS application is an effective strategy for enhancing IM/DD systems.
This method offers significant performance improvements, including increased receiver sensitivity and shaping gain.
The findings pave the way for more efficient optical communication systems utilizing IM/DD.