Generalized data-aided multi-symbol phase estimation for improving receiver sensitivity in direct-detection optical...

Area of Science:

• Optical communications engineering
• Digital signal processing
• Information theory

Background:

• Direct-detection optical communication systems often face limitations in receiver sensitivity.
• M-ary differential phase-shift keying (DPSK) is a modulation scheme used to increase data rates.
• Accurate phase reference extraction is crucial for optimal DPSK signal demodulation.

Purpose of the Study:

• To introduce a generalized data-aided multi-symbol phase estimation (MSPE) framework.
• To improve receiver sensitivity in direct-detection optical m-ary DPSK systems.
• To enable performance comparable to coherent homodyne detection without an optical local oscillator.

Main Methods:

• Derivation of data-aided MSPE algorithms for various DPSK formats (DQPSK, 8-ary DPSK, m-ary DPSK, DPSK/ASK).
• Simulations to evaluate receiver sensitivity improvements.
• Introduction of an electronic nonlinear phase shift compensation scheme for DPSK/ASK.
• Presentation of a universal receiver platform using optical I/Q demodulators and digital signal processing.

Main Results:

• Achieved receiver sensitivity improvements exceeding 2 dB using data-aided MSPE.
• Demonstrated that direct-detection m-ary DPSK performance can approach coherent homodyne detection.
• Showcased performance improvements in nonlinear transmission scenarios.
• Validated a simple and universal receiver platform for m-ary DPSK.

Conclusions:

• Data-aided MSPE offers a significant advancement for direct-detection optical DPSK systems.
• The proposed framework enhances receiver sensitivity and approaches the performance of more complex coherent systems.
• The universal receiver platform simplifies implementation for advanced DPSK systems.