Temperature and strain sensor based on weak LPG and fiber ring down

A fiber ring down with a weak long period grating for temperature and strain sensing is proposed and demonstrated. The sensing devices consist of two matched fiber Bragg gratings, a section of single mode fiber, a weak long period grating, a pulsed laser source and a photodiode. The LPG incorporated in fiber ring cavity is used as sensing element, the induced resonance wavelength shift of which will cause an additional loss in the cavity. As a result, the amplitude of applied temperature variation or strain can be obtained by simply measuring the fiber ring down time. The proposed sensing system has advantages of easy configuration and rapid response.