Research On The Measurement Technology Of Arm Length Difference Of Interferometric Fiber Optic Hydrophone Based On Microwave Photonics

Fiber optic hydrophone,as a key acoustic measuring instrument,has the characteristics of high sound pressure sensitivity and strong resistance to electromagnetic interference,which provides a more reliable technical guarantee for the sonar system.Interferometric fiber optic hydrophone as a kind of underwater acoustic fiber sensor,the determination of the arm difference is related to the accuracy of the sensor in the system measurement.At present,there is no more convenient method for measuring the arm length difference of the fiber optic hydrophone,so it is of great significance to reduce the difficulty and cost of the arm length difference measurement.Based on the idea of microwave photonics,the thesis proposes and designs an interferometric fiber optic hydrophone arm length difference measurement system,which is suitable for fiber optic hydrophones with Michelson and Mach-Zehnder interferometers as the basic structure.At the same time,it can adapt to the optical fiber hydrophone with different reflectivity,according to the light-borne radio frequency signal,the interference phenomenon of light occurs in the coupler and extract the arm length difference information through data processing.The thesis has carried out relevant functions and circuit design for each functional module in the system,such as light emitting module,radio frequency synthesis module,photoelectric detection module,power detection module and control module,and is integrated on a circuit board to complete the construction of the arm length difference measurement system.In data processing,not only the accuracy of the hardware is improved,but also the existing measurement data is used to improve the accuracy of the data measurement through interpolation and particle swarm optimization algorithms,which simplifies the actual measurement process of the arm length difference and reduces the cost of the test system.The thesis tests the performance of the proposed optical fiber hydrophone arm length difference measurement system.The performance of each module meets the system requirements and the system has a flat response in the range of 61-700MHz.Finally,the measurement system was used to measure the arm length difference of the Michelson optical fiber hydrophone.After the measurement data was processed,the arm length difference value reached 6 significant digits,and the measurement accuracy reached the ?m level.