SINGLE-MODE FIBER MULTITERMINAL STAR DIRECTIONAL COUPLER

We report the first single-mode multiterminal star coupler in which fibers are grouped into sets of three fibers. The three fibers in each set were than braided over some length before one or more of the fibers of each set are interchanged with their counterparts in other sets. We utilized the encapsulated etching technique reported earlier to overcome the peculiar geometric problems associated with single-mode fibers. Excellent output uniformity and very low throughput loss have been achieved in these devices because of our new designs. We also present coupled-mode theoretical analysis which can be used to describe these new single-mode star couplers.