Comb-Filter Based on In-Fiber Mach-Zehnder Interferometer Using a Twin-Core Fiber

A comb-filter based on in-fiber Mach-Zehnder interferometer (MZI) is experimentally fabricated by splicing a section of single mode noncircular twin-core fiber (TCF) between two single mode fibers (SMFs). The wavelength spacing between the adjacent transmission peaks was numerically and experimentally analyzed, and it is associated with the effective index difference of the two cores and the length of the TCF. The wavelength spacing between the adjacent transmission peaks can be narrowed by increasing the length of the TCF or the effective index difference of the two cores. This device is compact and easy to be fabricated.