MICRO-OPTIC DEVICES FOR FIBEROPTIC COMMUNICATIONS

A novel approach, ″micro-optics,″ is proposed to realize coupling/branching in fiber-optic communications. The operation is based on the beam transformation in a graded index rod (beam undulation and beam size change), in association with reflection or refraction at a graded index rod facet. Small-size couplers/dividers have been devised by inserting a semitransparent mirror between the facets of two graded index rods with a length of a quarter of the undulation period. Their best features are small size, simple structure, low insertion loss, and wide application areas. An excess insertion loss as low as 0. 5 dB has been realized in a 3-dB divider with SELFOC rods. As further applications of them, wavelength division multiplexers/demultiplexers have been developed by replacing the semitransparent mirror with a dielectric interference filter. An insertion loss of as low as 1. 2 dB and isolation of more than 20 dB for wavelength separation of 20 nm have been realized. Results are also shown on the other type of micro-optic couplers/dividers.