High-resolution Brillouin optical correlation domain analysis with no spectral scanning

Area of Science:

• Optics
• Fiber Optic Sensing
• Acoustic and Vibration Monitoring

Background:

• Traditional distributed Brillouin fiber sensors rely on spectral scanning to reconstruct the Brillouin gain spectrum (BGS).
• This spectral scanning process is time-consuming and requires prior knowledge of a reference BGS.
• An alternative approach is needed for faster and more efficient Brillouin sensing.

Purpose of the Study:

• To propose and demonstrate a new method for distributed Brillouin fiber sensing.
• To extract local Brillouin frequency shift (BFS) using temporal transient analysis.
• To eliminate the need for spectral scanning and prior BGS knowledge.

Main Methods:

• Utilizing temporal transient analysis of the step response of the amplified signal wave.
• Taking measurements at only two arbitrary frequency offsets between pump and signal waves.
• Applying analytic and numeric solutions of stimulated Brillouin scattering differential equations.

Main Results:

• Successfully measured the BFS of a 2-meter fiber with 1 MHz accuracy and 200 MHz dynamic range.
• Achieved 4 cm resolution in Brillouin optical correlation domain analysis (B-OCDA) with 2.4 MHz standard deviation and 100 MHz dynamic range.
• Identified a 4 cm hot-spot and addressed multiple correlation peaks in a single pump pulse flight.

Conclusions:

• The proposed transient analysis method offers a spectral-scanning-free approach to distributed Brillouin fiber sensing.
• This technique enables accurate BFS measurement and high-resolution B-OCDA.
• The method holds potential for random-access distributed and dynamic monitoring of sound and vibration.