Detection of Excited Vibration Signals on the Latticed Fence Structure Using a Distributed Fiber Optic Sensor with Sagnac Interferometer

To detect external vibration signals on the latticed fence structure, distributed fiber optic sensor using Sagnac interferometer was fabricated and tested. Because of easy construction Sagnac interferometer was selected rather than MachZehnder type. The latticed structure fabricated with dimension of 180cm in width and 180cm in height, the optical fiber, 50m in length, distributed and fixed on the latticed structure. For the detection of the excited vibration signals, single mode fiber, a laser with 1,550nm in wavelength, 3x3 coupler, PZT phase modulator were used. It was verified the sensitivity of the Sagnac interferometer using the PZT phase modulator. Fiber-optic external vibration signal applied to the latticed structure from 100Hz to several kHz. The interferometeric fiber optic sensor detected the excited vibration signal very effectively without any signal processing. The detected optical signals were compared and analyzed to the detected accelerometer signals against time and frequency domain. Based on the experimental results, distributed fiber optic sensor using Sagnac interferometer detected effectively external vibration signal and had a good performance. This system can be expanded to fiber optic latticed fence structure for the monitoring of a significant system.