Performance analysis of coherent optical 8-star QAM systems using decision-aided maximum likelihood phase estimation

Area of Science:

• Optical communications
• Digital modulation techniques

Background:

• Phase estimation errors significantly impact the performance of digital modulation schemes like 8-star QAM.
• Accurate bit-error rate (BER) analysis is crucial for designing reliable optical communication systems.

Purpose of the Study:

• To derive an approximate bit-error rate (BER) expression for 8-star quadrature amplitude modulation (QAM).
• To evaluate the impact of phase estimation error on 8-star QAM performance.
• To provide a tool for quick performance estimation and system optimization.

Main Methods:

• Derivation of an approximate BER expression for 8-star QAM.
• Verification using numerical integration of the conditional BER.
• Validation through Monte-Carlo (MC) simulations.

Main Results:

• An accurate approximate BER expression for 8-star QAM under phase estimation error was successfully derived.
• The derived approximation shows good agreement with numerical integration and MC simulations.
• The approximation facilitates efficient BER performance estimation.

Conclusions:

• The derived approximate BER expression offers a valuable tool for analyzing 8-star QAM performance in the presence of phase estimation errors.
• This approximation aids in predicting laser linewidth tolerance and optimizing system parameters like the ring ratio.