Crosstalk characteristics of optical add/drop multiplexers based on Mach-Zehnder interferometers with FBGs

We report an investigation of the homodyne/heterodyne crosstalk of optical add/drop multiplexers, based on Mach-Zehnder interferometers with fibre Bragg gratings, in wavelength division multiplexing systems. Two different types of gratings are studied, with different average refractive index perturbations, one constant and equal to zero and another non-uniform and negative. Two structures of the referred type are proposed to minimize the homodyne or heterodyne crosstalk.