Optical switching networks using tree‐structured waveguide optical switches

Abstract

AbstractTo make a large‐sized optical matrix is an important subject in realizing optical switching systems. Although optical matrices using waveguide optical switches have potential from the viewpoint of high speed and circuit integration, they are limited in the number of input/output terminals (up to between 4 and 8) due to the insertion loss and multiple crosstalk noise. To reduce these disadvantages, this paper offers optical switching networks using tree‐structured N x 1 waveguide switches as fundamental elements. Approximated equations for the insertion loss and the multiple crosstalk are given and it is shown that those in the proposed networks are approximately proportional to the number of stages in the tree structure. A 4 × 4 optical highway switch using Ti:LiNbO3 tree‐structured directional couplers was tested to confirm its switching capability. The experimental results obtained have a good agreement with the equations of the insertion loss and the multiple crosstalk characteristic. By using these equations, the size of the realizable switching system was estimated; a highway switch having 32 to 64 terminals is found to be possible with the present technology.