Optical delay lines realized with integrated optics are important elements for the realization of wavelength/frequency multiplexing and demultiplexing tasks in optical communication systems. As the channel spacing in the WDM/FDM communication networks is getting smaller and smaller, the polarisation dependence of the spectral response due to the waveguide birefringence of the optical delay lines becomes a serious problem.
In this project, we propose the realization of completely polarization independent optical delay lines fabricated by ion exchange in glass, done by inserting a passive integrated TE/TM polarization converter in the middle of the delay lines. The polarization converter, based on the photoelastic effect, will introduce an equal optical delay for TE and TM modes respectively thus permitting a completely polarization independent operation. The functioning of the delay lines will be demonstrated in the realization of a polarisation independent frequency (de)multiplexer, based on an asymmetrical MZ interferometer.