METHOD OF FABRICATING A FUSED-TYPE MODE-SELECTIVE DIRECTIONAL COUPLER

摘要

A method of fabricating a fused-type directional coupler that has stable characteristics in a simple manner. According to the embodiment of the present invention, two two-mode optical fibers (701, 702) having identical structures, one of which having a reduced cladding diameter by chemical etching and the other of which having a reduced core and cladding diameter by heated tapering, are fused by heating (704) and extended. The fused-type mode-selective directional coupler fabricated according to the present invention obviates the need to look for a particular pair of single mode-two mode optical fibers that satisfy the phase match condition. In addition, the mode-selective directional coupler of the present invention is more stable against change of temperature compared with conventional polished-type directional couplers that include material other than optical fibers and is easier to fabricate, because the mode-selective directional coupler of the present invention is an all-optical-fiber, fused-type directional coupler. Moreover, the present invention can be applied to fabrication of mode-selective directional couplers utilizing symmetrical high-degree modes such as LP02 mode as well as fabrication of mode-selective directional couplers utilizing asymmetrical high-degree modes such as LP11 mode.