kHz-order linewidth controllable 1550 nm single-frequency fiber laser for coherent optical communication

Area of Science:

• Optics and Photonics
• Optical Communications Engineering

Background:

• Coherent optical communication systems require lasers with precise linewidth control for optimal performance.
• Existing laser technologies may have limitations in achieving the desired linewidth stability and tunability for advanced modulation formats.

Purpose of the Study:

• To demonstrate a novel single-frequency fiber laser (SFFL) with kHz-order linewidth controllability.
• To investigate the effectiveness of using filtered white Gaussian noise (WGN) for linewidth tuning in a 1550 nm SFFL.

Main Methods:

• Implementation of an optical feedback loop incorporating a fiber stretcher modulated by a low-pass filtered WGN signal.
• Systematic variation of WGN signal amplitudes and cutoff frequencies to control the laser linewidth.
• Characterization of laser performance, including optical signal-to-noise ratio (OSNR) and relative intensity noise (RIN).

Main Results:

• Achieved kHz-order linewidth controllability over a wide range (0.8 to 353 kHz).
• Demonstrated high optical signal-to-noise ratio (OSNR) exceeding 72.0 dB.
• Attained relative intensity noise (RIN) approaching the shot noise limit (-148.5 dB/Hz at >40 MHz).

Conclusions:

• The developed kHz-order linewidth controllable SFFL is a significant advancement for optical communications.
• This laser technology is valuable for optimizing receiver sensitivity and bit error rate (BER) in high-order quadrature amplitude modulation (QAM) systems.
• The method provides a flexible and effective approach for linewidth management in fiber lasers.