Record bandwidth waveband-shift-free optical phase conjugation in nonlinear fiber optical loop mirror

Area of Science:

• Photonics
• Optical Communications
• Nonlinear Optics

Background:

• Optical phase conjugation (OPC) is vital for signal processing in optical communication systems.
• Existing OPC techniques often suffer from wavelength shifts, limiting their practical application.
• Broadband, wavelength-shift-free OPC is required for advanced optical networks.

Purpose of the Study:

• To propose and demonstrate a novel configuration for broadband, wavelength-shift-free optical phase conjugation (OPC).
• To enable phase-conjugated signals to occupy the same wavelength band as input signals.
• To achieve practical deployment of OPC in communication links.

Main Methods:

• Utilizing four-wave mixing in a nonlinear fiber optical loop mirror (NOLM).
• Implementing an input/output configuration where signals and pump return to the input port, while conjugated signals exit the output port.
• Employing a fiber Bragg grating to impart an asymmetric phase shift on the pump for signal demultiplexing.

Main Results:

• Experimental demonstration of waveband-shift-free OPC across a 35 nm bandwidth.
• Achieved extinction ratios between signals and conjugated copies ranging from 17 dB to 25 dB.
• Observed a 7 nm performance gap in the middle of the band, representing a record bandwidth for all-fiber setups.

Conclusions:

• The proposed NOLM configuration successfully achieves broadband, wavelength-shift-free OPC.
• The results indicate the feasibility of practical OPC deployment in communication links.
• Numerical simulations identified the cause of the performance gap, paving the way for future improvements.