Ultra-short FBG based distributed sensing using shifted optical Gaussian filters and microwave-network analysis

Area of Science:

• Optical Engineering
• Sensor Technology
• Materials Science

Background:

• Ultrashort fiber Bragg gratings (US-FBGs) show promise for distributed sensing.
• Their broad spectra limit traditional wavelength-based measurements.
• A novel interrogation concept using shifted optical Gaussian filters (SOGF) was developed for US-FBG measurements.

Purpose of the Study:

• To demonstrate the first US-FBG-based self-referencing distributed optical sensing technique.
• To leverage SOGF for US-FBG interrogation.
• To showcase advantages like adjustable sensitivity, high-speed detection, and robustness.

Main Methods:

• Implementation of a self-referencing distributed optical sensing system using cascaded US-FBGs.
• Integration of SOGF within a microwave network containing a fiber delay-line.
• Analysis of the network's complex frequency response to obtain time-domain response for differential detection.

Main Results:

• Successful demonstration of the US-FBG-based self-referencing distributed sensing technique.
• Achieved high-speed, wide-range intensity-based detection (>14000 με).
• Demonstrated resistance to nonuniform parameter distribution.
• Experimental validation with eight cascaded US-FBGs.

Conclusions:

• The proposed technique offers adjustable sensitivity and range, suitable for US-FBG measurements.
• US-FBGs enhance power budget and capacity in distributed sensing compared to conventional weak FBGs.
• This approach provides a promising avenue for advanced optical sensing applications.