Investigation of a Fibre Optic Frequency Shifter and Optical Isolator.

摘要

This report documents a programme of investigation of an in line fibre optic frequency translator and optical isolator on behalf of AFOSR (90-0286). The proposed designs are based on evanescent field coupling from a single mode optical fibre to a multi-mode planar waveguide overlay. The programme focused mainly on the development of a particular design of frequency translator and included extensive characterization of fibre optic overlay structures in general. Fabrication of the frequency translator based on bonding lithium niobate to a fibre block and polishing it thin to form the acousto optic overlay proved to be difficult and yields were low. Several devices were completed but frequency shifting was not observed due to severe attenuation of the surface acoustic waves. On a more positive note the overlay structures demonstrated excellent wavelength selective properties leading to the realisation of tunable high resolution (2nm) dropping filters and band pass filters. Such devices have many applications in communications, sensing and tuning of fibre lasers. Fibre optic components, Frequency translators, Optical isolator.