Environmentally stable fiber optic polarization maintaining couplers

In a fiber optical coupler package comprising a rigid substrate and at least two side-by-side optical fibers, each fiber having a core and a surrounding cladding, said fibers being joined side-by-side in a coupler region and each fiber extending axially to opposite sides of said coupler region to a region of fixation of said rigid substrate having a coefficient of thermal expansion substantially matched to that of said fibers, the improvement comprising:

• each of said optical fibers having said cladding, at each side of said coupler region, separately fixed at a primary region of fixation to a rigid mounting surface of said substrate using a rigid adhesive deposit,
• each optical fiber, at each of said primary region of fixation, extending over its respective rigid mounting surface with a side of each said fiber located in close proximity to, and in a substantially tangential relationship along a line with its mounting surface,
• said rigid adhesive deposit, disposed on opposite sides of the line of tangency, forming a pair of substantially identical masses with mirror symmetry contacting only a portion of said cladding's circumference, and
• each said adhesive mass joined to contiguous surface portions of said cladding and said mounting surface along said line of tangency, said masses effectively bonding said fiber to said mounting surface, at said primary region of fixation, in a manner that is asymmetrical relative to the central axis of said fiber but symmetrical relative to a surface defined by said central axis and said line of tangency.

A polarization maintaining fiber optic coupler package comprising:

• two polarization maintaining fibers joined side-by-side in a coupler region and each fiber extending axially to opposite sides of said coupler region, said fibers including a core, a stress field that produces a polarization maintaining effect, and a surrounding cladding, said stress field defining two principal axes corresponding to fast and slow eigenmodes,
• a rigid substrate with a coefficient of thermal expansion substantially matched to that of said fibers,
• multiple platforms adapted to form primary regions of fixation of said fibers extending from said coupling region over said platform,
• each of said optical fibers having said cladding, located in close proximity to its respective platform, separately fixed to said respective platform in a substantially tangential relationship along a line with its mounting surface,
• a rigid adhesive deposit, disposed in said primary region of fixation on opposite sides of the line of tangency, adapted to connect contiguous surface portions of said cladding to its mounting surface in a manner that does not completely cover said cladding with said deposit and is symmetrical relative to a surface defined by the central axis of said fiber and said line of tangency,
• secondary regions of fixation located on said substrate and extended axially farther outward from said primary regions of fixation, said optical fibers having a protective coating in regions overlapping said secondary region of fixation and extending outward, and
• rigid adhesive deposit adapted to connect said optical fiber through said protective coating to said substrate at said secondary regions of fixation.