Optical waveguides – With disengagable mechanical connector – Structure surrounding optical fiber-to-fiber connection
Reexamination Certificate
1998-05-07
2001-08-28
Bovernick, Rodney (Department: 2874)
Optical waveguides
With disengagable mechanical connector
Structure surrounding optical fiber-to-fiber connection
C385S082000
Reexamination Certificate
active
06280098
ABSTRACT:
The present invention relates to connectors for holding optical fibres, and in particular to a connector which allows two optical fibres to be repeatably optically coupled, decoupled and recoupled without any substantial change in optical performance.
In many optical applications, electromagnetic (e.g. laser) radiation is transmitted along optical fibres and thus must be coupled into the optical fibre at one end thereof.
One problem with coupling radiation into an optical fibre is that it is necessary to align the end of the optical fibre with a high degree of accuracy if transmission losses are to minimised. This is because of the small size of optical fibres which means that even small errors in the positioning of the end of an optical fibre can result in large energy losses when the radiation is coupled into the optical fibre end.
This problem is exacerbated if the fibre end is comtaminated with dust or dirt, as might be the case when the fibre is used in a non-clean environment. Such comtamination causes large energy losses and may result in an inoperable coupling to the fibre.
To help reduce the above problem a lens is often used to focus the incicent radiation beam onto the end of the optical fibre. The lens, in effect, magnifies the end of the optical fibre, thereby increasing its effective size. This reduces the sensitivity of the coupling to linear displacement between the fibre end and the incident beam and to contamination of the fibre end. Such an arrangement where a lens is used to magnify an optical fibre end is often referred to as an ‘expanded beam’ arrangement.
Typically the end of the optical fibre and the lens are mounted in an elongate cylindrical tube that holds the lens and fibre in a fixed, particular positional relationship to each other. This helps to avoid losses due to misalignment between the lens and fibre in use. This assembly is usually known as a lens barrel or lens tube. The lens tube is often arranged so that an emerging beam has a particular alignment (e.g. is centred) with respect to a datum surface, such as the longitudinal outside surface, of the lens tube.
However, such an expanded beam arrangement has increased sensitivity to angular misalignment (i.e. relative tilt) between the optical axis of the fibre and the optical axis of the incident beam which is being coupled into the fibre, because any such misalighment results in the lens no longer focussing the incident beam exactyly on the optical axis of the fibre. Rather, the focussed beam is displaced across the fibre end face, thereby leading to transmission losses. In an expanded beam arrangement such losses due to relative tilt between the optical axis of the fibre and the incident radiation beam are more significant than any losses due to lateral displacement between the optical axis of the fibre and the incident radiation beam. Therefore, even when using a lens tube, any coupling connector must ensure good angular alignment between the lens tube and incident light beam.
One way to achieve this is to have a connector having a throughbore which is sized to fit very snugly around the lens tube, such that the lens tube when inserted in the throughbore cannot tilt relative to the throughbore. By ensuring correct alignment of the connector throughbore with the incident radiation beam, tilt misalighment can be avoided. However, this arrangement requires precise and accurate construction of the connector, which can be difficult and expensive to achieve. Also, it can be difficult to insert the lens tube in the throughbore, because the necessarily tight fit means that any slight misalignment as the tube is inserted can result in the tube getting stuck in the bore. Also, any dirt or grit within the connector throughbore or on the lens tube will interfere with the fit and operation of the connector. This arrangement is not therefore really suitable for use in non-clean or more rugged environments.
Alternative methods of achieveing good alignment rely on adjusting or manipulating the relative position of the fibre within the connector once it is inserted therein. However, such adjustment can in practice be difficult and require more complex connector constructions. In many situations one would like to be able to couple radiation into an optical fibre without the need to carry out any adjustments. For example, it is often necessary to repeatedly couple and decouple an optical fibre, such as when adjusting components or moving equipment. It is not desirable to have to adjust the position of the fibre within a connector each time it is to be used.
According to a first aspect of the present invention, there is provided a connector for holding an optical fibre assembly, comprising:
a hollow body having a throughbore adapted to receive loosely the optical fibre assembly in use;
at least two discrete engagement means located at circumferentially spaced apart positions within the hollow body throughbore; and
biassing means engageable against an inserted optical fibre assembly in use to bias the assembly against the engagement means and thereby against the hollow body;
wherein the biassing means and engagement means are arranged such that the biassing means can be engaged against an inserted optical fibre assembly in use in such a manner that the optical fibre assembly engages only the biassing means and the engagement means and in such an arrangement is spaced apart from the inner surface of the hollow body throughbore.
The connector of the present invention has a throughbore having discrete having engagement elements or means against which an inserted optical fibre assembly can be biassed in such a manner that the assembly only engages the body of the connector via the engagement means (and the biassing means). This means that an optical fibre assembly can always be arranged to engage the same parts of the connector (i.e. the engagement means) and thereby have its longitudinal axis in the same orientation within the throughbore, whenever it is inserted in the connector. An optical fibre assembly can thus be repeatedly relocated in the connector with its longitudinal axis in the same orientation, without the need for alignment adjustment after the assembly has been inserted in the connector. As noted above, this is important because tilt of an assembly within a connector can lead to transmission losses. There is also no need for the connector to receive the assembly tightly to ensure reliably repeatable orientation.
The connector of the present invention can further ensure that an inserted optical fibre assembly only engages the discrete engagement means and the biassing means and is held spaced from the main inner surface of the connector throughbore in use. This makes the connector less susceptible to degradation caused by dirt or contamination within the connector body or on the optical fibre assembly, and thus particularly suited for use in more rugged, non-clean environments.
For example, in this aspect of the present invention contamination could only be a problem if it occurred on the relatively small contact surfaces of the engagement means, biassing means and corresponding regions on the assembly (as compared to arrangements in which the assembly contacts a connector over substantially all of its outer surface, where any contamination will almost invariably be a problem). Also, any sliding between surfaces as an assembly is inserted will tend to clean the surfaces and push the dirt into the gap between the engagement means and throughbore inner surface. Furthermore, the relatively small contact areas between the assembly and connector in use means that thee is a relatively high load at the contact points, which will tend to squeeze dust and dirt out from between the surfaces. Because the assembly is spaced from the throughbore surface, ther is space for this dirt to move to where it will not interfere with the holding of the assembly, unlike in more tight fitting systems where any moved dirt will tend to cause a problem elsewhere.
The connector of the present invention is suitable for any sort
Alcock Ian Peter
Pointer David James
Bovernick Rodney
Liniak Berenato Longacre & White
Point Source Limited
Stahl Michael J.
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