The Hydrophone Based on Fiber Bragg Gratings

• Main Authors: Li-Wei Chen, 陳立緯
• Other Authors: 劉文豐
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/7472xz

碩士 === 逢甲大學 === 電機工程學系 === 103 === The hydrophone based on fiber Bragg gratings is proposed in this research in which the main sensing elements include two fiber Bragg gratings with the similar bandwidth, reflectivity and central wavelengths. One of the two FBGs is packaged in the special packaged-structure and one end of the other FBG is connected to a 3dB coupler and the other end is linked to an InGaAs switchable gain detector. By means of opto-electronic energy transferring, the oscilloscope will show the voltage variation. The mechanism of the FBG hydrophone is that the acoustic waves with the frequency and intensity from the source in the water. The acoustic waves will push the water regular and then to vibrate the silicone diaphragm on the acrylic plate. Diaphragm vibration will cause the wavelength shift of FBG which is fixed on the silicone diaphragm. By using the InGaAs switchable gain detector, the optical signal will be converted into the electric signal to show this signal variation on the oscilloscope. From the voltage variation¸ we can know the acoustic frequency and the distance between the source and the hydrophone.