Free-running dual-comb fiber laser mode-locked by nonlinear multimode interference.

Area of Science:

• Photonics and Optical Engineering
• Fiber Optic Sensing
• Spectroscopy

Background:

• Dual-comb spectroscopy offers high-resolution spectral analysis.
• Existing systems often require complex phase-locking mechanisms.
• Cost-effective and simplified solutions are needed for widespread adoption.

Purpose of the Study:

• To present a simple, low-cost method for generating dual frequency combs from a single fiber-ring cavity.
• To demonstrate a simplified dual-comb spectroscopy system.
• To showcase its application in interrogating fiber Bragg grating (FBG) strain sensors.

Main Methods:

• Utilized nonlinear multimode interference within a single fiber-ring cavity.
• Employed a single-mode fiber-graded-index multimode-single-mode fiber structure as an all-fiber saturable absorber for mode-locking.
• Generated dual combs via dual-wavelength and polarization-multiplexed mechanisms.

Main Results:

• Achieved stable and simplified free-running dual-comb spectroscopy without complex phase-locking.
• Demonstrated the generation of two frequency combs with distinct comb spacings.
• Successfully applied the system for spectral determination of FBG-based strain sensors.

Conclusions:

• The proposed method offers a simple and low-cost approach to dual-comb generation.
• This technology provides a simplified platform for dual-comb spectroscopy.
• It presents a cost-effective alternative for interrogating FBG sensing networks.