<title>Low-cost planar optical couplers for large-core POF-based interconnects</title>

Abstract

ABSTRACT We propose to implement a modularly structured planar wave-guiding star-coupler for large-corepolymer fiber-based optical interconnect applications. An 8x8 version of the coupler is demonstrated using polymer materials. The planar star-coupler can be mass-produced using injection molding technology at substantially low cost. Measurements indicate that by properly working out a trade-offbetween device compactness, uniformity and coupling efficiency, a < 2.0 dB power fluctuation among all receiving channels and a 3. 1 dB excess power loss are obtainable. I. Introduction Recent surge of interest in polymer optical fibers (POFs) was powered by the belief that large core POF's may oneday become a cost-effective sub-local interconnect solution for many data communication applications [1]. It has beendemonstrated that material, production, as well as connection costs of POF's are appreciably lower than those of glassfibers. It is further believed that once POF's are widely accepted, their costs could become compatible to the costs of coppertransmission lines of inferior bandwidth. While research on finding low-loss POF materials and low-cost productionmethods is actively being pursued [2-3], attention has also been paid to low-cost connection schemes. Large core size, andhigh material flexibility provide many opportunities to decrease coupling and connection costs for POF's. Etched-mirror-based side-couplings have been used to couple light in and out of POF cost-effectively [4-5]. In the current work, wepropose a low-cost POF star-coupling structure which can be assembled in an un-controlled environment. In addition, theusage of this plug-and-play fiber optic component requires minimum training.A star-coupler is an important passive fiber optic component because it allows multiple signal broadcasts. A starcoupler can then be widely used in both time-division or wavelength-division based networks, such as optical buses [6-8].One way of fabricating a star-coupler uses a planar geometry where a one-dimensional (1D) flat cavity is sandwichedbetween an input and an output linear arrays of waveguides [9-1 1]. Such planar star-couplers for single-mode and multimodeglass fibers are now commercially available. Beside the high fabrication cost of such couplers, users need to pay anadditional cost of interfacing such couplers with conventional fibers. In the following section, we devise a planar POF star-coupler which uses cost-effective injection-molding fabrication technology, and requires no additional fiber interfacing cost.