Study of a fiber spectrometer based on offset fusion

Area of Science:

• Optics and Photonics
• Spectroscopy
• Fiber Optics

Background:

• Traditional spectrometers face limitations in resolution and size.
• Fiber-based spectrometers offer miniaturization potential.
• Speckle pattern analysis in optical fibers is an emerging technique for spectral recovery.

Purpose of the Study:

• To investigate a novel near-infrared spectrometer design utilizing offset fused multimode fiber (MMF).
• To analyze the impact of fiber offset fusion on spectrometer performance, specifically spectral correlation and resolution.
• To develop and apply algorithms for speckle noise reduction and spectral reconstruction.

Main Methods:

• Fabrication of offset fused fiber structures combining polarization maintaining fiber (PMF) and MMF.
• Experimental investigation of seven different vertical offset displacements.
• Implementation of dynamic threshold filtering for image denoising.
• Application of complete orthogonal decomposition for spectral reconstruction.
• Analysis of speckle images for spectral recovery.

Main Results:

• Fiber offset fusion significantly influences spectral correlation and resolution.
• Larger offset displacements excite more high-order modes in MMF, improving spectrometer performance.
• Increased mode excitation leads to lower correlation coefficients between spectral channels.
• The developed spectrometer achieved a spectral resolution of 0.6–0.016 nm.
• Offset fusion increases insertion loss, posing challenges for low-light detection.

Conclusions:

• Offset fused MMF is a viable approach for developing compact near-infrared spectrometers.
• Optimizing fiber offset is crucial for balancing spectral resolution and signal loss.
• Advanced denoising and reconstruction algorithms are essential for accurate spectral recovery from speckle patterns.