All-optical tunable multilevel amplitude regeneration based on coherent wave mixing using a polarizer

Area of Science:

• Optical communications
• Signal processing
• Nonlinear optics

Background:

• Multilevel amplitude modulation schemes like star-8QAM and star-16QAM are crucial for high-capacity optical networks.
• Amplitude noise and nonlinear phase noise degrade signal quality, limiting transmission performance.
• Existing regeneration techniques often require complex electronic components or are not fully optical.

Purpose of the Study:

• To demonstrate an all-optical, tunable, phase-preserving scheme for multilevel amplitude regeneration.
• To investigate the effectiveness of the proposed scheme for star-8QAM and star-16QAM signals.
• To assess the system's robustness against nonlinear phase noise in a deployed transmission line.

Main Methods:

• Utilizing coherent optical wave mixing with a polarizer for signal regeneration.
• Implementing the scheme for optical star 8-quadrature-amplitude modulation (star-8QAM) and star-16QAM signals with a 1:5 power ratio.
• Testing the amplitude regenerator in a 150 km transmission line experiencing nonlinear phase noise (Gordon-Mollenauer effect).

Main Results:

• Efficient suppression of amplitude noise on both higher and lower amplitude levels.
• Achieved a regeneration factor of nearly 5 for the higher-amplitude level of star-8QAM.
• Achieved a regeneration factor of 3 for the lower-amplitude level of star-8QAM.
• Demonstrated system robustness against nonlinear phase noise.

Conclusions:

• The proposed all-optical scheme effectively regenerates amplitude for multilevel signals.
• The technique offers efficient noise suppression and maintains phase preservation.
• The system shows promise for improving the performance and reach of optical communication systems.