Optical waveguides – With disengagable mechanical connector – Optical fiber/optical fiber cable termination structure
Patent
1995-06-20
1997-04-22
Lee, John D.
Optical waveguides
With disengagable mechanical connector
Optical fiber/optical fiber cable termination structure
385 84, 385 85, G02B 636
Patent
active
056235690
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to fibre terminations and especially to the termination of an optical fibre comprising a filament surrounded by a protective sheath, e.g. of a plastics or rubbery material. The filament usually has a glass core for the propagation of optical signals and a glass cladding to confine the signals to the core.
2. Related Art
At its ends an optical fibre is usually associated with external devices for optical intercommunication. It has been observed that reflections from the transfer face (i.e. the face of the fibre through which optical signals must pass for linkage with an external device) often cause operating difficulties. These difficulties are exacerbated if there are also reflections from the external device. Reflections to a signal generator can result in oscillation whereas reflections to a receiver can cause noise.
BRIEF SUMMARY OF THE INVENTION
It is an object of this invention to reduce the effect of such reflections.
This invention is based upon the principle that skewing the transfer face directs reflections received on the external path of the termination away from said external path whereby the reflections do not reach an external device located on said path. In so far as the reflections do not reach the external device, they do not affect its operation. However, skewing the transfer face causes refraction so that the external path assumes an arbitrary orientation which makes it difficult to locate the external device for coupling with the fibre. Therefore this invention also skews the core of the fibre to the direction of the external path and this angle of skew is chosen so that diffraction restores the external path to a predetermined direction, e.g. parallel to the geometric axis of the termination. Preferably the core ends on the geometric axis so that the external path is co-incident with the axis. It is particularly suitable for the angle of skew to be in the range 1.degree. to 20.degree. e.g. 8.degree. to 10.degree..
Conveniently, the termination includes a nose-piece which holds the end of the filament at the skew angle. The nose- piece is located in the housing of the termination. The nose-piece facilitates the assembly of the termination. In a preferred embodiment, the nose-piece has a counterbalance which causes it to tilt and adopt its angle of repose on the horizontal filament. As will be explained in greater detail below, the dimensions of the nose-piece determine the angle of repose so that the desired angle of skew is produced. After the fixing the nose-piece, e.g. by using a filler material such as a thermosetting plastics, it is convenient to cut or grind the end to establish the angle of the transfer face so as to cause the amount of refractive bending needed to orient the external path as described above.
The skewing of the core and the transfer face in accordance with the invention results in a termination which has the desirable features, e.g. the external path is parallel to and preferably co-incident with a desired axis, of a conventional termination but reflections are directed off the external path so that the effect on external devices is minimised.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described by way of example with reference to the accompanying drawings in which:
FIG. 1 is a diagram illustrating important orientations of the invention;
FIG. 2 illustrates in diagrammatic form further orientations at the end of a termination;
FIG. 3 is a longitudinal cross section through a nose-piece;
FIGS. 4A and 4B illustrate important dimensions of the nose-piece;
FIGS. 5A and 5B is a longitudinal cross section showing a nose-piece fixed to an optical fibre; and
FIG. 6 is a longitudinal cross section through an assembled termination in accordance with the invention.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
FIG. 1 illustrates the end portion of an optical fibre 10 which has a path region 11 and a transfer face 12. In the receive mode, optical signals exit the fibre 10
REFERENCES:
patent: 4615581 (1986-10-01), Morimoto
patent: 4695126 (1987-09-01), Cook
patent: 4787698 (1988-11-01), Lyons et al.
patent: 4802726 (1989-02-01), Palmquist et al.
patent: 5062682 (1991-11-01), Marazzi
patent: 5074638 (1991-12-01), Poli et al.
Hewlett--Packard Company
Lee John D.
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