Optical fiber point sensors based on forward Brillouin scattering

Area of Science:

• Optoelectronics
• Fiber Optics
• Acousto-Optics

Background:

• Forward Brillouin scattering enables sensing beyond fiber cladding.
• Quantitative point-sensing using this method was previously unreported.
• Standard optical fibers have limitations in external media analysis.

Purpose of the Study:

• To report the first quantitative forward Brillouin scattering point-sensor.
• To utilize a commercially available multi-core fiber for sensing.
• To analyze media outside the fiber cladding with high precision.

Main Methods:

• Employing pump light in an inner core to excite a guided acoustic mode.
• Utilizing photoelastic effects on a Bragg grating in an outer core.
• Analyzing refractive index perturbations and distinguishing liquids (ethanol/water).

Main Results:

• Achieved refractive index sensitivity to the tenth decimal point.
• Successfully differentiated ethanol and water outside the sensing region.
• Observed forward Brillouin scattering linewidths consistent with theoretical predictions.
• Confirmed spectral data integrity, unaffected by scattering outside the grating.

Conclusions:

• Demonstrated a functional forward Brillouin scattering point-sensor.
• Validated the use of multi-core fiber for precise external media analysis.
• Expanded the application scope of forward Brillouin scattering in optical fiber sensing.