Abstract

Signal distribution from one to several ports is necessary in various optical communication networks. To meet this requirement, a new integrated optical 1XN single mode star coupler is presented. The principle of operation is based on directional coupling of channel waveguides with linearly varying spacings¹. The design objective is to minimize the need for corner bends, and avoid the use of lossy γ-junctions. As a result, a minimum insertion loss is obtained for devices having all output channels equally spaced and perpendicular to a reference edge. Based on these design principles, three slightly different structures are developed, as shown in Fig.1A, B and C respectively. Essentially, the three patterns are based on the same concept of distributed coupling achieved by linearly increasing the wave­guide spacings in sets of two or three coupled waveguides. These configurations are designed to provide adequate spacing at the output end to accommodate for coupling to a fiber array. Device length is determined by the appropriate choice of the tilt angle α and the initial spacing c_j at the beginning of the various interaction regions. All three patterns are expected to satisfy the requirements, however, there are some trade-offs in certain design and fabrication situations.

© 1982 Optical Society of America