High Temperature Measurement with Low Cost, VCSEL-Based, Interrogation System Using Femtosecond Bragg Gratings

Area of Science:

• Optoelectronics
• Fiber Optic Sensors
• Materials Science

Background:

• Accurate and wide-range temperature measurement is crucial in various industrial and scientific applications.
• Existing Fiber Bragg Grating (FBG) interrogation systems face limitations in speed and temperature range.
• Vertical Cavity Surface Emitting Lasers (VCSELs) offer tunable wavelength capabilities but have inherent limitations.

Purpose of the Study:

• To develop a cost-effective and fast interrogation system for wide temperature measurement using FBGs.
• To overcome the narrow tuning range limitations of VCSELs in FBG sensing.
• To analyze the impact of VCSEL temperature instability on system performance.

Main Methods:

• Utilized a VCSEL with a High Contrast Grating (HCG)-based cavity for fast wavelength tuning.
• Implemented a system employing two femtosecond Bragg gratings for temperature sensing.
• Performed simulations for a system using sapphire Bragg gratings with wavelength and reflectance multiplexing.

Main Results:

• Demonstrated a proof-of-concept system capable of measuring temperatures from 25 to 800 °C.
• Analyzed the error introduced by VCSEL temperature instability.
• Proposed multiplexing strategies for enhanced measurement capabilities.

Conclusions:

• The developed VCSEL-based FBG interrogation system offers a cost-effective solution for wide-range, high-speed temperature measurements.
• The system's performance can be further enhanced through advanced multiplexing techniques.
• This technology has potential for applications requiring rapid temperature monitoring up to hundreds of kHz.