The present invention relates to fibre-optic packages and to methods of making fibre-optic packages.
Many types of fibre-optic package comprise a plurality of individual fibre-optic devices which are optically coupled together in series such that an output fibre of one individual fibre-optic device is coupled to an input fibre of another device. For example, two or three fibre-optic accelerometers of a type described in published international application PCT/GB2005/000078 (publication number WO 2005/068950 A1) may be coupled together by reflective couplers to form an accelerometer package for detecting components of acceleration along two or three mutually orthogonal directions.
Packages of this type are typically manufactured by arranging pre-fabricated devices within a package and then optically coupling individual devices together by fusion splicing of input and output fibres. Where another component (e.g. a fibre-coupled mirror) is required to be coupled into the optical path between two devices, two fusion splices are required: one to couple an output fibre of a first device to one end of the component, and a second to couple the other end of the component to an input fibre of a second device.
Fusion splicing is time consuming, complicated and expensive to carry out on a large scale. Two fibres have to be aligned, for example in a V-groove support, before being fused, for example by an arc. The expense of such splicing accounts for most of the cost of a finished package and this inhibits the commercial viability and take-up of fibre-optic packages in a number of potential applications. A fusion splice is also unreliable over time and a potential failure point in a finished package. Furthermore, fusion splices introduce additional undesirable optical loss. Additionally, the nature of the fusion splicing process is such that the fibres to be joined must be relatively long to allow for multiple failures during splicing and to allow use of fusion splicing machinery. This means that connecting fibres between optically adjacent devices in a package are generally much longer than is necessary for these fibres to perform their function. Excess lengths of fibre must then be stowed within the finished package, resulting in a package size that is unnecessarily large.
It is an object of the invention to ameliorate at least one of these problems. According to a first aspect of the present invention this object is achieved by a fibre-optic package comprising first and second fibre-optic devices or components having first and second optical fibres respectively, and wherein the first and second fibres are coupled by fused-fibre coupling.
In this specification, “fused-fibre coupling” of two fibres refers to the coupling of the two fibres by joining respective lengths of each fibre together such that, after coupling, a portion of radiation carried in one fibre may pass into the other fibre by evanescent coupling of radiation. Fused-fibre coupling may be achieved in a number of ways, for example by winding the two lengths of fibre around each other and then pulling them in a flame (i.e. fused-taper coupling), or by polishing the lengths of fibre and then gluing them next to each other.
The first and second fibre-optic devices or components may be fibre-optic devices of any kind such as temperature sensors, pressure sensors etc, or passive components such as in-fibre gratings. Since the first and second fibres are fused-fibre coupled, they can be of generally of shorter length in the finished package than would be the case if they were fusion spliced. This allows packages of the invention to be of reduced size compared to those in the prior art. The finished package is also more reliable since fused-fibre coupling provides coupling of greater longevity than fusion splicing. This is particularly important where the package is be deployed in inaccessible and/or dangerous environments.
The package may further comprise a third fibre-optic device or component having a third optical fibre wherein the third optical fibre is coupled to either the first optical fibre or to the second optical fibre by fused-fibre coupling. Where a package is required to have a device/component coupled to two other devices/components, this allows further package size reduction and increased reliability compared to prior art packages.
The first and second devices may be respectively first and second fibre-optic accelerometers and the third device a fibre-coupled reflector, the first and second fibres being respectively an output fibre of the first accelerometer and an input fibre of the second accelerometer and the package further comprising a second fibre-coupled reflector fused-fibre coupled to an input fibre of the first accelerometer and a third fibre-coupled reflector fused-fibre coupled to an output fibre of the second accelerometer. This provides a fibre-optic accelerometer package having two individual fibre-optic accelerometers.
To provide an accelerometer package having three individual fibre-optic accelerometers, the package may further comprise a third fibre-optic accelerometer having an input fibre fused-fibre coupled to the output fibre of the second accelerometer such that the third fibre-coupled reflector is coupled to the optical path between the second and third accelerometers, and a fourth fibre-coupled reflector fused-fibre coupled to an output fibre of the third accelerometer. Alternatively, the output fibre of the third accelerometer may be cleaved (or cleaved and then the exposed end silvered) to form a reflective end thereof.
The fibre-optic accelerometers are preferably oriented so as to detect components of acceleration of the package along substantially mutually orthogonal directions.
The fibre-coupled reflector or reflectors may each comprise a length of fibre having a cleaved end, or a cleaved and silvered end.
According to the first aspect of the invention, a fibre-optic package is provided, the package comprising first and second fibre-optic devices or components having first and second optical fibres respectively, and wherein the first and second fibres are coupled by fused-fibre coupling. The package may further comprise a third fibre-optic device/component directly optically connected to the first device/component by the first optical fibre. This provides the advantage that no coupling of fibres is required to optically connect the first and third devices/components. This may be achieved by fabricating the first and third devices together using a single length of optical fibre to form the first and third devices as well as the optical fibre connecting them.
The first and third devices may be respectively first and second fibre-optic accelerometers and the second device a fibre-coupled reflector, the package further comprising a second fibre-coupled reflector fused-fibre coupled to an input fibre of the first accelerometer and a third fibre-coupled reflector fused-fibre coupled to an output fibre of the second accelerometer. The first and second accelerometers may be formed using a single optical fibre.
To provide an accelerometer package having three individual fibre-optic accelerometers, a third fibre-optic accelerometer may be directly optically connected to the output fibre of the second accelerometer and a fourth fibre-coupled reflector fused-fibre coupled to an output fibre of the third accelerometer. For example, the three individual fibre-optic accelerometers may be formed with a single optical fibre. Instead of providing a fourth fibre-coupled reflector, the output fibre of the third accelerometer may be cleaved (or cleaved and then the exposed end silvered) to form a reflective end thereof.
The fibre-optic accelerometers are preferably oriented so as to detect components of acceleration of the package along substantially mutually orthogonal directions.
The fibre-coupled reflector or reflectors may each comprise a length of fibre having a cleaved end, or a cleaved and silvered end.
A second aspect of the invention provides a method of fabricating a fibre-optic package comprising the steps of:
The method may comprise the steps of:
(i) forming first, second and third individual fibre-optic accelerometers from a single optical fibre;
(ii) fused-fibre coupling a first fibre-coupled reflector to the fibre between the first and second accelerometers;
(iii) fused-fibre coupling a second fibre-coupled reflector to the fibre between the second and third accelerometers;
(iv) fused-fibre coupling a third fibre-coupled reflector to the fibre at an input of the first accelerometer; and
(v) fused-fibre coupling a fourth fibre-coupled reflector to the fibre at an output of the third accelerometer,
thus forming an accelerometer package.
The step of coupling two fibres may be effected by fused-taper coupling, i.e. by twisting a length of one of the fibres around a length of the other and heating the region in which the fibres overlap to form a coupled region. The coupled region is preferably packaged itself.
Embodiments of the invention are described below by way of example only and with reference to the accompanying drawings in which:
As shown in
Referring to
Referring to
Referring to
The fibre coupled reflectors 118, 120, 122, 124 and the portions of the fibre 116 to which they are attached are then individually packaged to form sub-packages 126, 128, 130, 132 which are stowed within the cradle 114 to form a substantially finished fibre-optic accelerometer package 100 of the invention, as illustrated in
Coupling of the fibre-coupled reflectors 118, 120, 122, 124 in the orientation shown in
Referring to
Referring to
The orientation of fibre-coupled mirrors 218, 220, 222, 224 defines fibre 216 as the input fibre of the finished accelerometer package.
Number | Date | Country | Kind |
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0520590.1 | Oct 2005 | GB | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/GB06/03668 | 10/3/2006 | WO | 00 | 3/18/2008 |