Experimental results demonstrate a sensing range of up to ∼80 km without optical amplification, accompanied by a position accuracy of 336 m. Clearly there is a need for a technique that allows continuous vibration measurements to be captured in real time over lengths from a few meters to tens or hundreds of kilometers. Distributed fiber-optic. For distributed fiber-optic sensors, slowly varying vibration signals down to 5 mHz are difficult to measure due to low signal-to-noise ratios. We propose and demonstrate a forward transmission-based distributed sensing system, combined with a polarization-generated carrier for detection bandwidth. To extract vibration information from phase modulation of light, two Mach–Zehnder interferometers (MZIs) are employed with a 3 × 3 coupler-based differential cross multiplication algorithm for phase calculation. Unlike traditional point-type vibration sensors, DVS realizes continuous, real-time. Fiber optic vibration sensors that use existing fiber optic cables laid for communication have the advantage of being able to collectively and accurately measure vibrations over a wide range along the cables1), 2), and in recent years, they have been attracting attention as a means of environmental.
