Optical waveguides – With disengagable mechanical connector – Optical fiber/optical fiber cable termination structure
Reexamination Certificate
1999-12-23
2001-11-20
Sikder, Mohammad (Department: 2874)
Optical waveguides
With disengagable mechanical connector
Optical fiber/optical fiber cable termination structure
C385S081000, C385S082000, C385S083000, C385S084000
Reexamination Certificate
active
06318905
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an optical connector element having a one-piece body.
It is known that an optical fiber includes a core which is the portion in which a light beam to be transmitted propagates, and that the core has a centering tolerance of about 0.8 &mgr;m (for single mode fibers) within the section of the fiber.
It is also known that an optical fiber is mounted in a connector element by being fixed in a sheath referred to as a “ferrule”, in which sheath the fiber is generally glued and then polished at its end, and that such mounting induces a centering tolerance of about 2 &mgr;m.
As a result, the position of the core of an optical fiber relative to its ferrule is subjected to a cumulative tolerance value which, when two fibers are to be connected together poses a problem because there is a high likelihood that the facing cores of the two fibers will not coincide.
To reduce this risk of non-coincidence, it is known that it is possible to perform a standardized angular positioning operation in the following manner, once the fiber has been set in resin in its ferrule, and its end has been polished.
The fiber held in the ferrule is presented to the end of a fiber mounted in an orientation plug. In the plug, the fiber has standardized eccentricity, i.e. its core is offset relative to the geometrical center of the outside section of the ferrule of the plug by a given distance in a given direction.
The ferrule is presented in a plurality of different angular positions facing the orientation plug. In general, four or six such positions are used which are angularly spaced apart by 90° or by 60°.
A light signal is transmitted between the fiber to be oriented and the fiber in the orientation plug, and the angular position in which the signal is transmitted best is chosen as being the optimum orientation.
The ferrule is then held stationary in a connector element in an angular position in which the fiber lies in its optimum orientation, by means for preventing it from rotating, which means are provided in the connector element.
Thus, when the fiber oriented in this way is connected to another fiber oriented under the same conditions, the cores of both of the facing fibers lie within the same angular sector.
It is also known that, in order for two coupled-together connector elements to guarantee good optical connection between two fibers, it is essential for the end faces of the two fibers to be held facing each other independently of the mechanical stresses to which the coupled-together connector elements might b subjected, which stresses can, in particular, result from handling one or more optical cables.
For that purpose, an alignment sleeve is used for the ferrules, and the inside of each connector element is organized to allow clearance between firstly the fiber and its ferrule and secondly the remainder of the connector element, so that the two ferrules held facing each other by the alignment sleeve inside the two coupled-together connector elements form an assembly which is capable of floating inside the coupled-together bodies of the two connector elements.
One difficulty with the optical connector elements lies in the need to hold the ferrules angularly while also allowing them to float inside each connector element.
OBJECTS AND SUMMARY OF THE INVENTION
An object of the invention is to provide a connector element that overcomes that difficulty, i.e. a connector element that leaves sufficient clearance for the ferrule but that enables the fiber to be oriented after it has been set in resin and polished.
The present invention provides an optical connector element having a coupling face for coupling to another optical connector element and comprising:
a) a ferrule serving to receive the end portion of an optical fiber;
b) a ferrule holder co-operating with the ferrule to form a continuous ferrule assembly;
c) a body receiving said ferrule assembly and open on the coupling face end so as to enable said ferrule assembly to be inserted into it;
d) resilient means tending to urge the ferrule assembly inserted into the body so that it is pushed back out of said body towards the coupling face of the connector element;
e) means for preventing the ferrule assembly from rotating relative to the body;
f) snap-fastening shapes on the ferrule assembly; and
g) snap-fastening shapes on the body;
wherein the snap-fastening shapes on the body are situated on that side of the resilient means which is closer to the coupling face, and they are mounted on the body in a manner such that they can retract reversibly.
In the context of the present invention, the term “coupling face” of a connector element is used to mean its face via which it is connected to another connector element.
In a particular embodiment of the invention, the snap-fastening shapes on the body are supported by elastically-deformable portions of the body.
In a preferred variant of the embodiment, the elastically-deformable portions of the body that support the snap-fastening shapes are constituted by the free ends of resilient beams cut out longitudinally in the thickness of the wall of the body.
An explanation follows of how the connector element of the invention makes it possible to overcome the difficulty resulting from the need to hold the ferrule angularly while also allowing it to float in the connector element.
It can be understood that, in the event of mechanical stress, the coupled-together connector elements can be displaced slightly relative to each other, which can give rise to the ferrules being tilted slightly relative to their respective bodies, and that such tilting leads to radial movement which is large remote from the end faces of the two ferrules but which is quite small in the vicinity of said end faces.
In the invention, the snap-fastening shapes are positioned on the coupling face end of the resilient means, which makes it possible to position them as close as possible to the facing end faces of the two fibers, and a relatively small amount of radial clearance between the snap-fastening shapes suffices to impart considerable freedom of movement to the ferrule assembly in the body of the connector element, while maintaining its angular indexing.
In addition, the fact that the snap-fastening shapes are situated on the front of the resilient means, i.e. on that side of the resilient means that is closer to the coupling face, facilitates access to said snap-fastening shapes, and in particular to those on the body that can retract, which makes it possible to release them so as to orient the fiber while testing various angular positions for the ferrule assembly in the body.
In order to reduce the number of parts making up the connector element of the invention, in a particular embodiment of the invention, the snap-fastening shapes on the body and on the ferrule assembly constitute an axial abutment which limits the axial displacement of the ferrule assembly in the body towards the coupling face of the connector element.
In this embodiment, the fact that the snap-fastening shapes provided on the body can be retracted makes it possible to mount the assembly made up of the ferrule and of its ferrule holder in the one-piece body of the connector element merely by engaging said assembly into the body, via its opening which is situated in the coupling face end of the body.
REFERENCES:
patent: 6010250 (2000-01-01), Sung
patent: 0366346 (1990-05-01), None
patent: 0571325 (1993-04-01), None
patent: 0819960 (1998-01-01), None
patent: 9535520 (1995-12-01), None
Causse Cyril
Valencia Laurent
Radiall
Schweitzer Cornman Gross & Bondell LLP
Sikder Mohammad
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