Characterising the inclusion of a fibre Bragg grating in a nonlinear optical loop mirror

Abstract

The self-switching capabilities of the nonlinear optical loop mirror (NOLM)1 fibre configuration have become an integral part of many all-optical signal processing applications2. In its operation as a single-wavelength device the switching is achieved by inducing unequal nonlinear phases in the two counterpropagating pulses in the fibre loop. The phase difference seen with recombination at the coupler results in reflection or transmission from the device, dependant upon the input intensity. A number of approaches have been suggested to achieve the required break in loop symmetry1,3-5, one of which reported experimentally 5, uses a fibre Bragg grating (FBG) spliced into the loop. The single-wavelength operation of this device was shown to provide wavelength discrimination in its switching characteristics.