Multiple connector for multi-fibre optic ribbons

A multiple connector for multi-fibre optic ribbons, comprising two facing plugs snap-insertable into a coupling consisting of a plurality of bushes locked together by a locking device, each of the plugs comprising a butting chamber and a plurality of ferrules complete with a support socket and a helical spring. The butting chamber, containing a plurality of individual optical fibres, also has a snap-cover and is fixed to a protection shell through which a multi-fibre ribbon is inserted.

BACKGROUND OF THE INVENTION 
This invention relates to a multiple connector for multi-fibre optic 
ribbons. 
Various types of multiple connectors are currently in use, usually in the 
form of two facing plugs enabling multi-fibre optic ribbons to be 
connected together. A ribbon containing at least two optical fibres is 
inserted into each of them. A fitting projection is provided at the end 
distant from that through which the ribbon is inserted, at the same end 
there also being provided two centering or guide elements. Said centering 
elements are in the form of a pin element and a hole, each located on one 
side of the fitting projection, to be inserted into the hole or to receive 
the pin element of the other connector respectively. 
To connect the multi-fibre ribbon to another multi-fibre ribbon the two 
plugs are positioned facing each other. More specifically, two fitting 
projections internally containing individual fibres of the multi-fibre 
ribbon are coupled together. To achieve good connection, said individual 
fibres of both plugs must be aligned, this being possible because of the 
centering elements. 
In addition to centering the two fitting projections, the centering 
elements also lock the pair of plugs. In this respect, the connection is 
achieved by respectively inserting the two pin elements into the two holes 
of each of said facing plugs. Although the described locking element, i.e. 
a pair of pin elements and holes on each plug, allows easy connection it 
has the drawback of likewise easy disconnection. This can accidentally 
happen as a result of a simple pull on the cable or multi-fibre ribbon, 
with consequent loss of transmission. To obviate this drawback a clip is 
provided embracing the two facing plugs to retain them in position. 
A further drawback is the need to align individual fibres. As the fibre 
core diameter is just a few microns it is very difficult to simultaneously 
align two or more fibres to ensure a good connection. 
An object of the present invention is to provide a multiple connector which 
achieves multiple connection of optical fibres while using a space less 
than that currently necessary. 
A further object is to achieve a multiple connection by means of several 
independent connections, made as separate connections. 
A further object is to facilitate the mounting of the connector by 
eliminating bonding by adhesive or ultrasound. 
A further object of the invention is to ensure correct operation and good 
positioning of the movable parts during coupling, uncoupling and 
operation. 
A further object is to provide a valid locking element which prevents any 
accidental uncoupling of said connectors due to pulling on the cable. 
SUMMARY OF THE INVENTION 
These objects are attained by a multiple connector for multi-fibre optic 
ribbons, comprising two facing plugs snap-insertable into a coupling 
consisting of a plurality of bushes locked together by a locking device, 
each of said plugs comprising a butting chamber and a plurality of 
ferrules each complete with a support socket and a helical spring, said 
butting chamber having a cover and containing a plurality of individual 
optical fibres.

DETAILED DESCRIPTION OF THE INVENTION 
FIGS. 1 and 2 show a multiple connector for multi-fibre optic ribbons 
according to the present invention, indicated overall by the reference 
numeral 10. 
The connector 10 consists of two facing plugs 11 snap-inserted into a 
coupling 12. This latter interposed between the plugs 11 acts as a locking 
element and also as the element which connects them together. 
At that end of the plug 11 distant from the end to be inserted into the 
coupling 12 there is a butting chamber 13 with a snap-cover 14. The 
chamber 13 is connected to a protection shell 15 of rubber or another 
similar material, through the interior of which a cable or ribbon 16 also 
comprising outer protection is inserted. The ribbon 16 is a multi-fibre 
ribbon containing at least two optical fibres, and in particular four in a 
preferred embodiment. 
FIGS. 3 and 4 show in detail the manner in which the connector 10 is 
butt-coupled to the ribbon 16. 
The plastics components of the connector 10 are formed by moulding, and to 
facilitate subsequent assembly are provided with elastic projections. 
Before commencing the butt-coupling operation, the coupling 12 and plugs 11 
are preassembled. Preassembly of the coupling 12 consists of inserting 
four bushes 17 into the coupling 12, i.e. into its shell. When said bushes 
17 have been inserted they are locked by a locking device 18 which is 
inserted as an interference fit. The locking device 18 is designed and 
inserted into the shell of the coupling 12 such that the bushes 17 are 
locked but remain floating. 
Preassembly of the plugs 11 consists of inserting four ferrules 19 each 
complete with a support socket 20 and a helical spring 21 into the body 31 
of the plug 11. The springs 21, located behind the support socket 20 in 
the direction of a contact zone 22, urge the ferrules 19 towards said zone 
22 so as to ensure good contact between them, i.e. between two respective 
ferrules 19 of the two facing plugs 11 when the multiple connector 10 is 
connected, i.e. in its working position. 
The butt-coupling of the ribbon 16 is commenced by preparing the so-called 
cord head, i.e. that potation of said ribbon 16 to be used for the 
connection. 
To be able to make the connection the outer sheathing 23 of said portion of 
the ribbon 16 is stripped off. This exposes a layer of kevlar strands 24, 
the ribbon 16 then being inserted through the protection shell 15 and into 
the butting chamber 13. 
To ensure proper fitting of the butting chamber 13 to the protection shell 
15, this latter is mounted on a knurled support 25 on said chamber 13. A 
recess 26 is provided in an outer surface of the knurled support 25 to act 
as a seat for a projecting inner edge 27 of the protection shell 15. 
Having mounted the shell 15 to face the butting chamber 13, the projecting 
inner edge 27 is inserted into the recess 26. When the bare portion of the 
ribbon 16 has been properly inserted into the butting chamber 13, a tube 
29 previously mounted on the cord is slid to cover the knurled support 25 
on the butting chamber 13. Two crimping operations are then carried out, 
one at the knurled support 25 covered by the kevlar and the other at the 
outer sheath 23. In this manner the ribbon 16 is securely anchored to the 
butting chamber 13 and hence to the plug 11. 
Having anchored the ribbon 16 it is separated into its four constituent 
fibres 30, and the primary coating is stripped from them. The fibres 30 
prepared in this manner are inserted through the respective four ferrules 
19 of the plug 11. A syringe is used to inject the resin for their 
bonding. Finally said butting chamber 13 is snap-closed by the cover 14. 
In the final stage the fibres projecting from the ferrules are cut and then 
polished by automatic lappers. A series of optical and dimensional checks 
is then carried out to ensure high-quality performance. 
The coupling 12 interposed between the two plugs 11 is formed in such a 
manner as to ensure both good contact between respective fibres 30 of the 
two facing plugs 11 and permanent coupling between them. Retention between 
the parts is provided by a push-pull connection which enables the multiple 
connector to be coupled and uncoupled by applying a simple axial force. 
One of the advantages of the multiple connector for multi-fibre optic 
ribbons is its geometrically planar structure. In this respect the 
arrangement of the four ferrules is rectilinear and individually 
retractable to form four independent connections, with the possibility of 
floating each of them. 
A further advantage is a completely open fibre introduction chamber which 
is inspectionable at any moment. 
A further advantage is the plastics construction of the connector parts. In 
this respect, the moulding process enables the holes within which the 
ferrules with their respective support sockets and the bushes slide to be 
made perfectly smooth and free of impressions and mould closure signs. In 
addition the use of various elastic fitting projections enables bonding by 
adhesive or ultrasound to be completely eliminated, with the advantage of 
simpler and more reliable mechanical connections. 
An important advantage is the method for fixing the ferrules to the plug 
body by a moulded plastics device incorporating reopenable snap-fitting. 
By virtue of this structure the assemblies can if necessary be reopened 
using a simple tool, so enabling the ferrules or bushes to be recovered. 
A further advantage is the coupling release push-pull device formed in such 
a manner as not to increase the overall size of the connector. In addition 
such a coupling eliminates accidental release of the plugs resulting from 
a simple pull on one or both ribbons. 
A further important advantage is the small dimensions of the multiple 
connector according to the present invention compared with conventional 
connectors.