Research On Wavelength-Division Multiplexing Of Interferometric Fiber Optic Signals

As one of the most efficient schemes, wavelength division multiplexing (WDM) is applied widely in fiber-optic sensor arrays. After the investigation of different WDM schemes which have been applied in hydrophone arrays at present, one system of interferometric fiber-optic hydrophone using WDM technique is designed and it's mainly components are two wavelength multiplexers, which are engaged to add and drop different wavelength. The structure and theory of this scheme are workable in the system of WDM including more wavelengths. It's easy to hybrid with space-division multiplexing and time-division multiplexing (TDM) for large-scale multiplexing of hydrophone arrays.In a practical arrays, the number of hydrophone needs to be 256-1024, WDM and TDM will be adopted, some problems, such as the crosstalk between different hydrophones, power loss and some nonlinear effects when the optic power in the fiber is higher, must be solved seriously. Thinking about the practical application, the performance of some crucial components in this system has been researched roundly, and the testing results about the performance of correlative components also have been received. Some nonlinear effects, such as SBS, FWM, SPM, in our system have been analyzed in theory. The effect of them has been put forward; moreover, some measures for retraining them have been indicated too.The crosstalk in different WDM systems is analyzed and calculated. Through analyzing the damage of crosstalk to our system, the isolation index of demultiplexer is also limited accordingly. When the isolation of wavelength division demutiplexer is 40 dB, the crosstalk level in our WDM system is about -70 dB.The WDM system has been built and tested. The result of testing indicates that our system is better in performance, and sound signal can be detected well and truly using this system. The phase resolution of our system is 10-5 rad / Hz . Crosstalk level in our system is very lower, profiting from the high isolation levels of wavelength division demutiplexer, which is about 40 dB under the static testing. The result of testing accords with theoretical analyze.In any case, the results of our research are helpful for the application of large-scale multiplexing of hydrophone arrays in theory and practice.