Distributed multi-parameter sensing utilizing Brillouin frequency shifts contributed by multiple acoustic modes in...

Area of Science:

• Optoelectronics and Photonics
• Fiber Optic Sensing Technology
• Materials Science for Optical Fibers

Background:

• Distributed sensing of temperature and strain is crucial for structural health monitoring and various industrial applications.
• Standard single-mode fibers (SMF) are widely available but typically support only a single acoustic mode for sensing.
• Existing methods often struggle with simultaneous and accurate discrimination between temperature and strain measurements.

Purpose of the Study:

• To propose and experimentally demonstrate a multi-parameter optical-fiber sensor capable of distributed temperature and strain measurement.
• To utilize multiple acoustic modes within the stimulated Brillouin scattering (SBS) effect in standard single-mode fiber (SMF).
• To investigate the feasibility of achieving discriminative measurement of temperature and strain by analyzing different acoustic modes.

Main Methods:

• Theoretical analysis of Brillouin gain spectrum (BGS) properties related to guided optical and acoustic modes by manipulating fiber doping and refractive index profiles.
• Simulation of multiple acoustic mode excitation in SMF and analysis of their impact on the BGS.
• Experimental validation using two different standard single-mode fibers (SSMF), analyzing their multi-peak BGS and Brillouin frequency shifts.

Main Results:

• Simulations confirmed the excitation of multiple acoustic modes in SMF, resulting in multi-peak BGS.
• Unequal temperature and strain sensitivities were observed for different acoustic modes, proving discriminative measurement capability.
• Experimental results successfully demonstrated the discrimination of temperature and strain, with a specific SSMF achieving high accuracy (0.98 °C, 19.6 με) over a 20 km range.

Conclusions:

• The proposed multi-parameter sensor based on multiple acoustic modes in SBS is effective for distributed temperature and strain measurement using SSMF.
• Fiber structure parameters significantly influence measurement accuracy, highlighting the importance of tailored fiber design.
• The demonstrated technique offers a promising approach for advanced fiber optic sensing applications requiring simultaneous environmental parameter monitoring.