Anomalous Properties of Cascaded Photonic Crystal Fiber Based Long Period Gratings

摘要

We have demonstrated the Photonic Crystal Fiber (PCF)-based Long Period Grating (LPG) by machanical stress, in which each groove of the microbending will induce a local index change in the fiber via the photoelastic effect and such gratings can be completely erased by removing the pressure from the fiber. A Mach-Zehnder interferometer (MZI) formed by cascading a pair of PCF-based LPGs has been investigated in details in this paper for the application as an all-PCF filter. Because of the microstructured air holes, the effective index shows strong wavelength dependence, which will result some different properties distinguished with conventional optical fiber and we can expect some novel characteristics of this grating device. However, in the previous work, sensitive interference spectrum was only observed when stripping off the acrylate coating, which make the fiber device very fragile. And the coupling characteristics have not been analyzed in details yet. Cascaded LPGs were demonstrated to form a MZI, where multiple resonances were eaisly obtained without stripping the acrylate fiber coating by applying a much larger stress. The cascaded PCF-based LPGs have performed anomalous grating characteristics. This grating device offers the unique advantages of being tunable, erasable, reconfigurable and good interfering efficiency makes it promising applications in WDM communication.