Design and Construction of Tunable Band Pass Filter Using Hybrid FPMZI

Abstract

A novel design of hybrid Fabry-Perot Mach-Zehnder inline fiber interferometer with low cost and easily implemented structure is proposed and investigated theoretically and experimentally in this work. The proposed structure consists of two fiber Bragg gratings of 1546.13 and 1546.15 nm central reflection wavelengths respectively connected to two ends of an etched multimode fiber. The multimode fiber was etched using HF acid to get five different cladding sizes (120, 112, 90, 73, and 69 mm). The whole interferometer behavior was studied experimentally using 1546.7 nm pulsed laser and FBGA interrogator as a visualizer. Boundary mode analysis behavior of the same structure wave was studied theoretically using fine element method to calculate the total energy spectrum for the five temporal durations of etching. The modal distribution of this structure with TEM_pm, was characterized too. It was found that the FPMZI interferometer can be used efficiently as a narrow Notch pass filter in integrated optical communication systems since it has high sensitivity in the pm range. The central wavelength of the allowed band was tuned over the range (98-766 pm). The narrower rejection band was equal to 179 pm when MMF was etched for 20 min to remove 52.467 mm from the clad