A novel Sagnac fiber sensor

摘要

It is well known that as a measurement device, Sagnac fiber interferometer has the advantages of high measuring sensibility and strong antijamming ability. However, it is precisely because of the high sensibility, the measured change range of sensed quantities is usually very small. And also because of the strong antijamming ability, the fiber of Sagnac interferometer can not be used as a sensor. The reason is that the sensed signal well be eliminated by the signal cancellation effect between the two directions in Sagnac interferometer like the disturbance signal. This paper presents a novel Sagnac fiber sensor. It is added two devices into the common Sagnac fiber loop, one is the phase compression device and another is the birefringent fiber sensor. The phase compression device consists of a time delay fiber and a piezoelectic ceramic twisted around by Sagnac fiber. This device can realize the phase compression by which the measured range of sensed quantities is widely extended. The birefringent fiber sensor consists of a short section of high birefringent fiber. The method of adding the birefringent fiber sensor is selecting suitable position on Sagnac fiber loop and breaking off the fiber, then melting and linking the two break surfaces with the short section of high birefringent fiber. Not like the common fiber, there is not cancellation effect on the birefringent fiber. So the Sagnac interferometer can become a sensor. This kind of Sagnac fiber sensor has the advantages of high measuring precision, wide measured range, strong antijamming ability and simple structure.