Aiming at lower cost and further miniaturization, we developed a new optical coupling system for use as an optical interface of a parallel optical interconnect module, called ParaBIT-1. It consists of a new-structure 24-fiber bare fiber (BF) connector whose main parts are made of molded plastic and a 24-channel optical coupling component using new polymeric optical waveguide film. To prevent bare fibers from breaking, the BF connector plug has a fiber protector. This BF connector can be joined by direct physical contact between bare fibers in fiber guide holes with a 250-µm pitch. The buckling forces of the fibers themselves secure the physical contacts. The average measured insertion loss of the 24-fiber BF connector was 0.05 dB, and the return losses were over 35 dB. The optical coupling components are composed of a 24-ch polymeric optical waveguide film with 45 mirrors and the 24-fiber BF connector interface, and can be assembled by passive alignment. The high thermal stability of the film allows soldering, and the film is fabricated by direct photo patterning. The average insertion losses of the components for transmitter and receiver modules were 1.28 and 1.35 dB, respectively.

We have studied the basic optical and physical characteristics of polymeric optical waveguide films with S-shaped waveguides and 45 mirrors applied as multimode optical interconnection components. The core and cladding of the waveguide films were made of deuterated-polymethylmethacrylate (d-PMMA) and UV-cured resin, respectively. We evaluated the insertion losses of the waveguides, the crosstalk and the 45-mirror losses in these waveguide films and demonstrated that they have low propagation loss. The shrinkage and thermal expansion of the polymeric optical waveguide films are also discussed because of the interest in improving module packaging.