Tunable add/drop filters using LiNbO 3

Acousto-optical tunable filters (AOTFs) have the potential to be used in many advanced WDM systems. The wavelength add/drop multiplexing (ADM) system is one of the basic systems for wavelength division multiplexing (WDM) networks. A TE/TM mode conversion type of AOTF in LiNb03can enable ADM on a single chip and has been developed in earnest (1)(2)' (3). ADM systems require tunable filtering, narrow channel spacing, low cross-talk suppression, multi-wavelength filtering, low driving power, and a low insertion loss. There remain some problems to be solved, however, before AOTFs can be commercially practical for ADM. The most serious of these problems are to achieve a narrow bandwidth with a low side lobe, to decrease the driving power, and to prevent acousto-optical interactions between simultaneously applied signals. The AOTF consists of polarizing beam splitters, straight optical waveguides for TE/TM mode conversion, a SAW guide, a transducer, and SAW absorbers. In this paper, I would like to discuss how to resolve these problems from the compornent level.