All-optical multilevel amplitude regeneration in a single nonlinear optical loop mirror

Area of Science:

• Photonics
• Optical Communications
• Nonlinear Optics

Background:

• Pulse amplitude modulation (PAM4) is crucial for high-speed optical data transmission.
• Signal degradation due to noise and distortion limits transmission distance and performance.
• All-optical signal regeneration offers advantages in speed and power efficiency over electronic methods.

Purpose of the Study:

• To demonstrate all-optical amplitude regeneration of PAM4 signals.
• To investigate the performance of a single nonlinear optical loop mirror (NOLM) for this application.
• To analyze noise suppression and signal quality improvement.

Main Methods:

• Utilized a single nonlinear optical loop mirror (NOLM) configuration.
• Employed narrow pulse-width return-to-zero (RZ) pulses to create four power-plateau regions.
• Integrated highly nonlinear fiber (HNLF) for significant nonlinear phase shifts.
• Quantified noise suppression and error vector magnitude (EVM) improvement.

Main Results:

• Achieved four distinct power-plateau regions necessary for PAM4 regeneration.
• Demonstrated effective noise suppression across all amplitude levels.
• Obtained an overall EVM improvement of 0.92dB through optimization.
• Validated experimental findings with theoretical analysis of the nonlinear transfer function.

Conclusions:

• The single NOLM is a viable device for all-optical PAM4 amplitude regeneration.
• Optimizing input power and distortion strength enhances regeneration performance.
• The study provides insights into the design principles for NOLM-based optical regenerators.