A novel Sagnac fiber optic sensor employing time delay estimation for distributed detection and location

A novel Sagnac fiber optic sensor employing time delay estimation for distributed detection and location is proposed and demonstrated. The sensor employs Sagnac interferometer as interfering unit. A broadband, low-coherence source is spectrally sliced into two wavelength bands using wavelength division multiplexer. Therefore, the sensor consists of two Sagnac interferometers, multiplexed with a broadband light source, interfering unit and sensing fiber by wavelength division multiplexer, and hence four detected signals with two different wavelengths are obtained. After the demodulation scheme based on 3×3 coupler, two signals with fixed time delay are achieved and the location of the disturbance gained by time delay estimation enables the localization comparably accurate. Experimental results show that the sensor is especially advantageous for low location error to the application of intrusion detecting.