Research On OADM With Fiber Grating Coupler Structure

Optical Add-Drop Multiplexer (OADM) is nodal point of Wave Division Multiplexer (WDM). Performance of WDM relies on the performance of OADM device. Most of recent OADM device are not all-fiber device, so applications of those device are limited. Therefore, the all-fiber OADM device—Fiber Grating Coupler (FGC) is reported. There are four types of FGC: FGC based on Mach-Zehnder interferometer, asymmetric FGC based on 100% coupler, asymmetric FGC based on mismatched coupler and symmetrical FGC based on 100% coupler.In this paper, symmetrical FGC based on 100% coupler and FGC based on Mach-Zehnder interferometer are analyzed. Moreover, FGC based on Mach-Zehnder interferometer is tested.Super-mode theory is used to analyze the symmetrical FGC based on 100%. Come to the conclusion that, the optimum function of device reached when the grating with 1/4 length of coupler start at the middle of the coupler.The transmission matrix theory is used to analyze the FGC based on Mach-Zehnder interferometer. Parameters of device is defined and discussed. The FGC based on Mach-Zehnder interferometer is tested. The features of this device are 1550.006nm center wavelength, 88.598%max drop efficiency, 0.146nm 3dB bandwidth, -13.19dB return loss and 0.36dB total loss. In addition, this device used as ODM and OAM is tested respectively. Isolation of the device can reach 35dB and add efficiency is about 80%. The results of experiment matched the results of theory very well.