US 2001/0017962 A1 · Method of fabricating a fused-type mode-selective directional coupler

Abstract

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 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 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.

Claims12

Dependent claims

A method of fabricating a fused-type mode-selective directional coupler in which a mode-coupling ratio between a first mode M1 and a second mode M2 equals a certain value, the method comprising the steps of:

preparing a first optical fiber and a second optical fiber, the first and second optical fibers each having a core and a cladding, parts of a jacket of each of the first and second optical fibers being removed, the first optical fiber having a cladding diameter of D1 and a normalized frequency of V1, and the second optical fiber having a cladding diameter of D2 and a normalized frequency of V2, said V1 being less than said V2;
putting in contact the claddings of the first and second optical fibers to form a junction;
measuring the mode-coupling ratio between the first mode M1 of the first optical fiber and the second mode M2 of the second optical fiber;
extending the first and second optical fibers in longitudinal directions while fusing the junction;
and
stopping extending the first and second optical fibers when the mode-coupling ratio between the first mode M1 and the second mode M2 reaches the certain value.

3 more elements

Dependencies are inferred from the claim text.

Method of fabricating a fused-type mode-selective directional coupler

Life of this patent

Method of fabricating a fused-type mode-selective directional coupler

Life of this patent

Abstract

Claims12