Pair of Mechanically Induced Long Period Fiber Gratings as MultiChannel Notch Filters

Abstract

A pair of mechanically induced long period fiber gratings formed over an optical fiber
forms a series of interference fringes centered on the cladding mode resonant stop bands of the
grating spectrum. The fringe space separation depends on the separation between the MLPFGs.
The formation of interference can be explained by assuming the optical path through the core
and cladding of the fiber as the two arms of a Mach-Zehnder interferometer. The depth of the
notches can also be varied by the application of pressure over the gratings. The device can be
used as multi channel notch filter for wavelength division multiplexing applications.