Optical waveguides – With optical coupler – Particular coupling structure
Patent
1993-08-18
1995-04-25
Healy, Brian
Optical waveguides
With optical coupler
Particular coupling structure
385 31, 385 32, 385 24, 385 42, 385 48, 385 39, 385134, G02B 624
Patent
active
054106281
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to means for transferring light between an optical fibre housed within a fibre management unit and an external optical device, and in particular to a probe for tapping out light from optical fibres in a splice tray.
2. Related Art
An optical fibre splice tray usually houses many (typically 16) spliced optical fibres. In the typical case, therefore, it has 16 input fibres, 16 output fibres and 16 splices, each splice joining respective input and output fibres. In determining the quality of the splices, it is necessary to measure the light passing along the associated input and output fibres, and this is often difficult to do, particularly where access to a splice tray is hampered, as is the case where splice trays are mounted in racks. Thus, in order to make measurements on one of these fibres, using a conventional power meter, it is necessary to remove that fibre from the tray, which inevitably means disturbing all the fibres, with the attendant possibility of compromising the integrity of the signals carried by these fibres.
This situation can be improved by using a splice tray having only two spliced fibres. This considerably reduces the possibility of disturbing the signals carried by fibres other than that being measured. Unfortunately, the fibre being measured must still be removed from its normal position in the tray, which means that there is still a high risk of imposing unacceptably high bending losses on the fibre being measured. Consequently, measurement cannot be carried out whilst the fibre is carrying signals (that is to say whilst the system is "live").
BRIEF SUMMARY OF THE INVENTION
The present invention provides transfer means for transferring light between an optical fibre housed within a fibre management unit and an optical device external to the fibre management unit, the transfer means comprising an aperture formed in the fibre management unit, and a probe housing the optical device, wherein the probe is provided with an optical head in optical communication with the optical device, and with means for moving the optical head into the aperture so as to deform the optical fibre against a mandrel sufficiently to permit light to be tapped between the optical fibre and the optical head, the mandrel being positioned, in use, so that the optical fibre lies between the mandrel and the aperture.
This form of light transfer means reduces the risks of measuring fibres in situ, and measurements can be made without taking off-line the system of which the splice under test forms a part.
In one preferred embodiment, the mandrel is mounted within the probe. Alternatively, the mandrel is mounted in the fibre management unit adjacent to the aperture and positioned so that the optical fibre lies between the mandrel and the aperture.
Advantageously, the probe comprises a housing and a support carrying the optical head, the support being movable relative to the housing thereby constituting the means for moving the optical head. Conveniently, a slide constitutes the support, and the housing is provided with locating lugs for locating the probe relative to the aperture. Preferably, the lugs are resilient. The lugs may be such as to clip onto the edges of the aperture, and may be provided with V-shaped recesses for holding and guiding an optical fibre.
In a preferred embodiment, the optical head is a recessed block made of a transparent material, the recess having a V-shaped cross-section. Preferably, the V-shaped recess is defined at two surfaces of the block which are inclined to one another by an angle lying within the range of from 150.degree. to 179.degree..
For detector applications, it is advantageous for said angle to lie within the range of from 160.degree. to 175.degree., the angle being at the lower end of the range for low insertion loss detection, and at the upper end for very low less detection. For launch application, however, it is preferable for said angle to lie within the range of from 150.degree. to 160.degree
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Drouet Dominik
Ferguson David A.
Frost Peter L. J.
Kerry John
Paton Colin R.
British Telecommunications public limited company
Healy Brian
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