Optical modulation format conversion from one QPSK to one BPSK with information-integrity-employing phase-sensitive...

Area of Science:

• Optical Communications
• Signal Processing
• Photonics

Background:

• Quadrature Phase-Shift Keying (QPSK) and Binary Phase-Shift Keying (BPSK) are crucial modulation formats in optical communication systems.
• Improving signal quality and receiver flexibility is essential for next-generation networks.

Purpose of the Study:

• To propose and simulate a novel scheme for converting 20 Gbps QPSK signals to 20 Gbps BPSK signals.
• To maintain information integrity during the modulation format conversion.
• To investigate the potential of phase-sensitive amplifiers (PSAs) in this conversion process.

Main Methods:

• Development of a theoretical framework for a degenerate phase-sensitive amplifier (PSA) acting as a phase de-multiplexer.
• Decomposition of QPSK signals into In-phase (I) and Quadrature-phase (Q) components using the PSA.
• Parallel-to-series conversion of I and Q components to generate a BPSK signal.
• Simulation-based verification and performance analysis.

Main Results:

• The proposed conversion scheme effectively restrains phase noise, as evidenced by constellation diagrams.
• Bit-error rate (BER) performance of the converted BPSK signal is superior to the original QPSK signal.
• The converted BPSK signal maintains original information integrity across varying input signal qualities.
• Error Vector Magnitude (EVM) and BER measurements confirm performance improvements compared to back-to-back BPSK.

Conclusions:

• The developed modulation format conversion scheme successfully converts QPSK to BPSK with enhanced BER performance and preserved information integrity.
• The use of PSA as a phase de-multiplexer is validated for signal decomposition and noise suppression.
• The scheme offers potential applications in enhancing signal BER and enabling flexible transmitter/receiver designs in software-defined networks.