Temperature-insensitive refractive index sensor based on tilted moiré FBG with high resolution.

Area of Science:

• Optoelectronics
• Fiber Optic Sensors
• Nanotechnology

Background:

• Fiber Bragg gratings (FBGs) are widely used in sensing applications.
• Tilted FBGs (TFBGs) offer enhanced sensitivity by coupling light into cladding modes.
• Existing TFBGs have limitations in resolution and temperature cross-sensitivity.

Purpose of the Study:

• To propose and fabricate a novel tilted moiré FBG (TMFBG) sensor.
• To enhance the resolution and temperature-insensitivity of FBG-based refractive index sensors.
• To investigate the performance of the TMFBG for high-precision refractive index detection.

Main Methods:

• Fabrication of a TMFBG sensor consisting of two consecutive scribed TFBGs.
• Adjustment of Bragg wavelengths and tilt angles of the TFBGs to achieve non-overlapping cladding mode combs.
• Utilizing the TMFBG for refractive index detection and evaluating its resolution and temperature performance.

Main Results:

• The fabricated TMFBG exhibits non-overlapping cladding mode combs in its transmission spectrum.
• The TMFBG sensor achieves a refractive index resolution of 2 × 10^-7 RIU.
• The sensor demonstrates an order of magnitude improvement in resolution compared to single TFBGs.
• The TMFBG shows good performance regarding temperature-insensitivity.

Conclusions:

• The proposed TMFBG is a highly effective sensor for ultra-high resolution refractive index detection.
• The TMFBG sensor offers significant advantages over conventional TFBGs in terms of resolution and stability.
• This technology holds promise for advanced applications requiring precise refractive index measurements.