Simultaneous measurement of refractive index and temperature based on intensity demodulation using matching grating...

Area of Science:

• Photonics
• Optical Sensing
• Fiber Optics

Background:

• Accurate simultaneous measurement of solution refractive index (SRI) and temperature is crucial for various scientific and industrial applications.
• Existing methods often face limitations in terms of accuracy, cost, or suitability for in situ monitoring.
• Fiber optic sensors offer a promising alternative due to their robustness and multiplexing capabilities.

Purpose of the Study:

• To demonstrate a novel sensor system for simultaneous measurement of SRI and temperature.
• To utilize an intensity-demodulation system based on the matching grating method.
• To develop a compact, cost-effective, and in situ applicable sensor.

Main Methods:

• A long period grating in photonic crystal fiber (LPG-PCF) was used for wavelength-dependent intensity transmission.
• Two fiber Bragg gratings (FBGs) were employed: one etched (sensitive to SRI and temperature) and another (FBG2) only sensitive to temperature.
• A matching FBG, identical to FBG2, was used to isolate SRI and temperature signals through intensity changes.
• A signal processing unit deduced SRI and temperature by monitoring output lights from unmatching and matching paths.

Main Results:

• The sensor successfully demonstrated simultaneous measurement of SRI and temperature.
• The system effectively translated wavelength shifts of FBGs into measurable reflection intensity changes.
• Experimental results validated the functionality of the proposed sensor system.

Conclusions:

• The developed sensor system provides a reliable method for simultaneous SRI and temperature measurement.
• The use of LPG-PCF and FBGs in an intensity-demodulation setup offers a compact and cost-effective solution.
• The sensor is well-suited for in situ applications requiring simultaneous monitoring of refractive index and temperature.