CONNECTEUR MAGNETIQUE POUR CABLES OPTIQUES

MAGNETIC CONNECTOR FOR OPTICAL CABLES

Abrégé anglais

Abstract:
A magnetic connector for optical cables comprises a
pair of identical connector members of non-ferromagnetic material
fitted to the respective cable ends and adapted to be brought
together to align the ends of the fibres of the respective cables.
Toroidal magnets mounted on the connector member produce mutually
assisting magnetic fields parallel to the alignment of the fibre
ends, which are covered by ferromagnetic material and so are held
firmly together by the fields. A liquid of suitable refractive
index may be interposed between the fibre ends to avoid optical
discontinuities.

Revendications

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A connector for coupling together a pair of light-
conducting cables each comprising a plurality of optical fibres
to be joined to corresponding fibres of the other cable,
comprising:
a pair of housings of nonmagnetic material having
closely juxtaposable confronting end faces, each of said housings
further having an entrance port remote from the end face thereof
and a plurality of channels extending from said entrance port
toward said end face, said channels terminating in wider recesses
opening onto said end faces;
retaining means securing an optical cable to the
entrance port of each of said housings with each fibre of each
cable guidedly traversing one of said channels and terminating
at said end face of the respective housing in an extremity
laterally movable in the corresponding recess, said extremity
being peripherally coated with a tubular ferromagnetic layer;
locating means for relatively orienting said end
faces to bring corresponding fibre extremities of said cables
within their respective recesses into substantial alignment
with each other upon juxtaposition of said housings; and
active magnetic means for inducing in the interior of
the juxtaposed housing a magnetic field substantially perpend-
icular to said end faces generating in said ferromagnetic
layers a flux for precisely aligning said corresponding fibre
extremities with each other.
2. A connector as defined in claim 1 wherein said active
magnetic means comprises a pair of annular magnets respectively
surrounding said housings with aiding polarities.
3. A connector as defined in claim 2 wherein said annular
magnets are flush with said end faces for coming into mutual
contact upon juxtaposition of said housings.

4. A connector as defined in claim 1, 2 or 3 wherein
said locator means comprises a projection on each end face
and a complementary depression on the respective other end face.
5. A connector as defined in claim 1, wherein said
retaining means comprises a clamping nut engaging the entrance
port of each housing.
6. A connector as defined in claim 5 wherein said
retaining means further comprises an elastic sleeve surrounding
said clamping nut and bearing upon an unclamped portion of the
respective cable.
7. A connector as defined in claim 1, 2 or 3 wherein
said housings are mutually identical.

Description

1~1371~
The present invention relates to optical fibres and is
particularly concerned with a magnetic connector for optical
cables, i.e. light conducting cables, comprising one or more
optical fibres.
A very important practical problem, which arises when
optical fibres are used in transmission systems, is to make good
connections between fibre trunks in order to minimize coupling
losses.
These losses are caused both by imperfect alignment of
the fibre ends to be connected, i.e. by lack of parallelism and
by lateral misalignment of the fibre axes, and also by the dis-
continuity in refractive index near the junction point.
In order to align the fibre ends, devices having sleeve
guides or V-groove guides, in which the fibres are held in the
correct position by adhesives or resilient means, are generally
used, and matching of the refractive index is effected by suit-
able liquid substances interposed between the fibre ends.
These devices, while satisfactory for permanent splices,
present a number of problems when used in connectors, since the
delicacy of their structure does not permit the frequent joining
and separating operations typically required with connectors.
These problems are mitigated by the present invention
of a magnetic connector for optical cables, whose main feature is
its easy placement at the cable ends, allowing connection to be
made without difficulty and with good alignment between the
single optical fibres. Another feature of the connector is that
it does not require mechanical parts having exacting requirements
of accuracy or calibration but may be carried out by means of two
identical parts, thereby reducing the production costs to a
minimum.
According to the present invention a connector for
coupling together a pair of light-conducting cables each
comprising a plurality of optical fibres to be joined to
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corresponding fibres of the other cable, comprises: a pair
of housings of nonmagnetic material having closely juxtaposable
confronting end faces, each of said housings further having an
entrance port remote from the end face thereof and a plurality
of channels extending from said channels toward said end face,
said channels terminating in wider recesses opening onto said
end faces; retaining means securing an optical cable to the
entrance port of each of said housings with each fibre of each
cable guidedly traversing one of said channels and terminating
at said end face of the respective housing in an extremity
laterally movable in the corresponding recess, said extremity
being peripherally coated with a tubular ferromagnetic layer;
locating means for relatively orienting said end faces to
bring corresponding fibre extremities of said cables within
their respective recesses into substantial alignment with each
other upon juxtaposition of said housings; and active magnetic
means for inducing in the interior of the juxtaposed housing
a magnetic field substantially perpendicular to said end faces
generating in said ferromagnetic layers a flux for precisely
aligning said corresponding fibre extremities with each other.
One embodiment of the present invention will now be
described by way of example with reference to the accompanying
drawing, which is a central longitudinal sectional view of a
magnetic connector in accordance with the invention.
In the drawing, CO and CO indicate the optical ends
of a cable to be connected. Each end comprises, for example,
three optical fibres indicated respectively by Fl, F2, F3 and
Fl , F2 , F3 .
ReferencesC and C denote two housings made of non-
ferromagnetic materials, in which the optical fibres of the
cable are located. These housings are provided with means
S and S for locking the optical cable, stuffing boxes for
example, and with resiliently fitting means G, G , for
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preventing the establishment of concentrated mechanical stresses
on the cable near the connector.
Reference L and L denote two pins or projections
which key into complementary cavities N and N thereby to allow
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alignment of the connector parts while preventing at the same
time any relative rotation between them.
References M and M' denote two permanent magnets of toroidal
shape. The magnetic fields inside the materials present flux
lines parallel to the rotational axis of the magnets such that,
when the two connector parts are placed face to face in the con-
nected position shown, the fields are in the same sense.
Lastly, Rl, R3, R3, and Rl', R2', R3' denote cylindrical
coverings of ferromagnetic material, placed on the single fibre
ends; their function will be explained during the description of
the connector operation.
The application of these coverings may be effected by means
of simple mechanical processes or by utilizing well-known methods
of chemical or electrochemical deposition.
The assembling of each connector part at the respective end
-~ of the optical cable does not present particular difficulties,
since it consists simply in inserting the single fibres, already
bared of the protective coating and covered at the ends with the
cylindrical coverings of ferromagnetic material, in the guides
provided in the housings C, C' and in locking the optical cable
by the stuffing boxes S and S'.
At this point, the connector parts may be brought together
so as to align the protrusions L and L' with the cavities N and
N'. The magnets M and M' since they produce parallel and con-
cordant magnetic fields, effect a mutual attraction and therefore
the two connector parts keep firmly together.
If the magnetic attraction is insufficient> the two con-
nector parts may be kept in position by means of a bayonet joint,
a threaded locking ring or any other well-known device.
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The ends of fibres Fl, F2 and F3, already roughly pre-aligned
by the cylindrical guides located in the housings C and C', are
facing the corresponding ends of fibres Fl', F2' and F3' and are
separated from the latter by a thin gap. Their accurate alignment
is achieved by the magnetic field, lying parallel to the axes of
the fibres and produced by permanent magnets M and M'. In fact,
in consequence of the induced magnetization in the ferromagnetic
coverings placed on the fibre ends, a mutual attraction between
the facing fibres and alignment of the respective ends along the
flux lines of the magnetic field are obtained.
Through a suitable choice of the ratio of the magnet length
to its diameter, an essentially constant field parallel to the ro-
tational axis of the magnets can be obtained. Therefore the fibre
alignment can reach a mechanical accuracy otherwise not obtainable
except by means of complicated laboratory apparatus.
In order to a~oid any discontinuity in the refractive index,
a fluid of suitable refractive index is interposed between the
- fibre ends. It may be dripped inside the connector through an
opening provided in the housing C or C' for the purpose.
The above description has been given by way of example and
not in a limiting sense. Variations and modifications may be
made without departing from the scope of the invention. More
particularly, the connector may present not only axial symmetry
with radially arranged fibres, but also any prismatic shape with
the fibres arranged on superimposed planes.
Moreover, the magnetic field may be produced both by per-
menent magnets and by an electromagnet or solenoid having any
shape, provided that the flux lines are parallel to the single
optical fibre ends.
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