Tailoring Mach–Zehnder Comb-Filters Based on Concatenated Tapers

An all-fiber comb-filter using a Mach-Zehnder interferometer based on concatenated tapers is presented. The central wavelength, the amplitude, the period, and the spectral width of the transmission interference pattern can be tailored by varying the diameter and length of the waist, the length of the up- and down-transition of the fiber tapers, and the separation between the two tapers. Depending on the geometrical parameters of the tapers, the central position and span of the spectral interference pattern were tailored in the range of 1200-1650 and 50-300 nm, respectively. By varying the interferometer length, the fringe period and bandwidth were tailored between 3-36 and 2.5-11 nm, respectively. The physical length of the devices fabricated ranges from 15 to 30 mm. The proposed device is simple and suitable for applications in optical communications systems, fiber lasers, and optical fiber sensors for the monitoring of strain and displacement.