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Optical Subassembly Bore Press Fit Design for Close Tolerance

IP.com Disclosure Number: IPCOM000122495D
Original Publication Date: 1991-Dec-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 2 page(s) / 58K

Publishing Venue

IBM

Related People

Ives, RN: AUTHOR [+4]

Abstract

The diametrical clearance between the ceramic bore and the ferrule in single mode (SM) fiber-optic technology is typically 1.0-3.5 u. These tight tolerances are required for consistency in the power coupled into a fiber. To achieve this performance, the ferrule is usually 2499.5+/- 0.5 u and the ceramic bore is 2502 +/-1 u. It is frequently desirable to press fit the bore into the optical subassembly (OSA) body. Mechanical finite element analysis indicates that typical press fit designs result in several microns of "choking" in the bore where the ferrule engages. A typical design that has this weakness is shown in Fig. 1. So that the ferrule and the bore do not interfere due to this choking, the bore has to be flared at the press fit end, as seen in Fig. 1.

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Optical Subassembly Bore Press Fit Design for Close Tolerance

      The diametrical clearance between the ceramic bore and
the ferrule in single mode (SM) fiber-optic technology is typically
1.0-3.5 u.  These tight tolerances are required for consistency in
the power coupled into a fiber.  To achieve this performance, the
ferrule is usually 2499.5 0.5 u and the ceramic bore is 2502 1
u.  It is frequently desirable to press fit the bore into the optical
subassembly (OSA) body.  Mechanical finite element analysis indicates
that typical press fit designs result in several microns of "choking"
in the bore where the ferrule engages.  A typical design that has
this weakness is shown in Fig. 1.  So that the ferrule and the bore
do not interfere due to this choking, the bore has to be flared at
the press fit end, as seen in Fig. 1.  This operation is difficult to
control and can result in too much bore-to-ferrule clearance, hence
poor coupled power consistency because of variable ferrule placement
(ferrule "rattle").

      Disclosed is the design in Fig. 2 which alleviates this choking
concern since that area of press fit is occupied by the ring stop.
While finite element analysis does indicate a small amount of
choking, it is less than 1 u in the ferrule engagement area, which is
within the above-mentioned tolerances.  Hence the ceramic bores used
can be a constant diameter, therefore, achieving a lower bore cost
and tighter tolerance control.