A fan-in/out polymer optical waveguide is fabricated for connecting multimode multicore (7 cores) fiber with onedimensionally
aligned parallel optical components such as a VCSEL/PD array or a multimode fiber ribbon, which is
fabricated using the Mosquito method. The Mosquito method we have proposed is a fabrication technique for circular
and graded index (GI) cores. One of the unique characteristics of the Mosquito method is a capability of forming threedimensional
wirings. In the fan-in/out waveguides, high-density hexagonal alignment of 7 cores at one end is converted
to one dimensional alignment with a wider pitch at the other end. For realizing the fan-in/out waveguides, we have issues
about low insertion loss, low crosstalk, and the connectability with multicore fibers and optical components. In this paper,
we focus in the pitch accuracy of the fan-in/out waveguide. In the Mosquito method, the viscosities of the core and
cladding monomers are an important factor of the core figure and the core alignment because the viscosities have a
relation to monomer liquid-flow, which could devastate the core alignment. Hence, we investigate the influence of the
viscosities of the core and cladding monomers on the interchannel pitch accuracy of the fabricated fan-in/out polymer
optical waveguide. With increasing the viscosities of core and cladding monomers, the pitch accuracy is improved, while
the appropriate monomer viscosity conditions that can fix all the issues: core circularity and pitch accuracy in both ends
still needs to be investigated.
We successfully fabricate multi-channel GI circular-core polymer waveguides with precisely controlled pitches utilizing the Mosquito method. The Mosquito method is a very simple method for fabricating GI-core polymer optical waveguides that utilizes a micro dispenser. In this method, a viscous core monomer is directly dispensed into a cladding monomer layer before UV cured, and circular cores are formed by curing both the core and cladding under a UV exposure. Here, it is a concern that a needle position accuracy influences on the interchannel pitch when parallel cores are fabricated by parallel repetitive scan of a single needle. However, we succeeded in controlling the pitch with the Mosquito method and then, GI-core waveguides with 250.7±5.2 μm, 126.7±2.6 μm and 61.7±3.4 μm are successfully fabricated for the pre-set values of 250 μm, 125 μm and 62.5 μm, respectively. Then, we demonstrate a 4 × 10 Gbps transmission over the fabricated GI-core waveguide by connecting the waveguide to an MMF ribbon with a 250-μm pitch, which is realized because the pitch of the fabricated waveguide is accurately controlled to 250 μm.