All-optical modulation format conversion from on-off-keying to multiple-level phase-shift-keying based on...

Area of Science:

• Optical Communications
• Nonlinear Optics
• Signal Processing

Background:

• Non-return-to-zero on-off-keying (NRZ-OOK) is a common optical modulation format.
• Return-to-zero (RZ) phase-shift-keying (PSK) offers advantages in spectral efficiency and noise resilience.
• Efficient modulation format conversion is crucial for flexible optical networks.

Purpose of the Study:

• To propose and demonstrate an all-optical scheme for converting NRZ-OOK to RZ-PSK.
• To investigate the performance of this conversion for various PSK levels (binary, quadrature, 8-level).
• To validate the proposed scheme through numerical simulations and experimental tests.

Main Methods:

• Utilizing the inherent nonlinearity of optical fiber for modulation format conversion.
• Numerical simulations to assess the feasibility of NRZ-OOK to RZ-8-level PSK conversion.
• Experimental demonstration of NRZ-OOK to RZ-binary PSK conversion at 10.7 Gb/s.
• Experimental verification of NRZ-OOK to RZ-quadrature PSK conversion at 10.7 Gsymbol/s using eye opening measurements.

Main Results:

• Achieved error-free operation for NRZ-OOK to RZ-binary PSK conversion at 10.7 Gb/s.
• Demonstrated successful NRZ-OOK to RZ-quadrature PSK conversion, evidenced by clear eye diagrams after balanced detection at 10.7 Gsymbol/s.
• Confirmed the feasibility of NRZ-OOK to RZ-8-level PSK conversion via numerical simulation.

Conclusions:

• The proposed all-optical scheme effectively converts NRZ-OOK to RZ-PSK formats.
• The method is viable for high-speed optical communication systems.
• This technique offers a promising solution for flexible modulation format adaptation in future optical networks.