FBG Interrogator Using a Dispersive Waveguide Chip and a CMOS Camera

Area of Science:

• Optical Sensing
• Photonics
• Sensor Technology

Background:

• Fiber Bragg gratings (FBGs) offer advantages over electronic sensors, including electromagnetic interference immunity and suitability for harsh environments.
• Current FBG interrogation systems are often complex and costly, hindering widespread adoption.
• Developing cost-effective and practical interrogation methods is crucial for advancing FBG sensor technology.

Purpose of the Study:

• To present a novel, clean, and cost-effective method for interrogating FBG temperature sensors.
• To demonstrate the feasibility of using a waveguide spectral lens (WSL) and a standard CMOS camera for FBG interrogation.
• To evaluate the performance of the proposed system against a commercial optical spectrum analyzer (OSA).

Main Methods:

• Development of an interrogation system utilizing a micro-chip waveguide spectral lens (WSL) and a CMOS camera.
• Projection of the FBG transmission spectrum onto the camera without free-space optical components.
• Implementation of data processing techniques, including direct spatial shift analysis and deep neural network training, for temperature sensing.

Main Results:

• The WSL-camera system demonstrated comparable wavelength-temperature sensitivity (6.33 pm/°C) to a commercial OSA (6.32 pm/°C).
• Direct data processing achieved a sensitivity of 0.44 μm/°C based on the spatial shift of FBG spectra.
• A deep neural network achieved a temperature resolution of 0.1 °C (60-120 °C), significantly outperforming direct valley detection (7.84 °C).

Conclusions:

• The proposed WSL-camera hardware and data processing methods offer a compact, practical, and low-cost solution for FBG interrogation.
• This technology has the potential to significantly reduce the cost and complexity of FBG sensor systems.
• The developed system paves the way for broader applications of FBG sensors in various fields.