Optical waveguides – With disengagable mechanical connector – Optical fiber to a nonfiber optical device connector
Patent
1997-01-14
1998-12-22
Palmer, Phan T.H.
Optical waveguides
With disengagable mechanical connector
Optical fiber to a nonfiber optical device connector
385 94, G02B 636
Patent
active
058526960
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the packaging of an optical device in alignment with an optical fibre.
2. Related Art
The importance of accurate alignment of an optical fibre with other components in optical devices is well known. In an optoelectronic device such as a transmitter or receiver, for example, alignment of an optical fibre with a laser or receiver chip is necessary to attain optimum coupling of light energy. This is especially true for transmitters, where, for example, good optical coupling permits a laser to be operated using minimum current, thus reducing the heat generated during lasing and extending the life of the laser. Thermal expansion problems inherent in transferring heat from the laser are also minimised and, for some applications, packaging costs can be reduced through elimination of the need for a thermoelectric cooler.
In fabrication, not only must the fibre be aligned in three co-ordinates for optimum coupling, but this alignment must also be fixed by a rigid securement and must not be altered by shrinkage forces during fixation or subsequent processing. For a single mode fibre, for example, final alignment must generally be held to within plus or minus one-half micrometer in dimensions radial to the fibre and to within one to two micrometers axially.
Conventionally, packages which incorporate environmentally sensitive components such as lasers, for example, are hermetically sealed to provide the component with a closed and protected environment. It is customary to introduce a communicating optical fibre into such packages via a suitable feed-through connection. In fabrication, the fibre is first inserted into the feed-through and the feed-through is secured to the package. The portion of fibre internal to the package is then aligned with the laser, or other component, and separately fixed in position. U.S. Pat. No. 4615031, for example, discloses one such fabrication technique in which an anchorage clamp welded over the fibre inside the package is used to fix the alignment.
A similar approach to packaging an optical device is described in European patent application EP-A-0286319, where an optical fibre is hermetically sealed in a feed-through tube which is aligned with a laser through an aperture in a wall of a package. The feed-through tube has two supporting points, mounted on an inner surface of the package, at which the tube can be manoeuvred to align it with the optical device. The fibre in the tube is actively optically aligned with the laser by powering up the laser and monitoring the level of light which passes along the fibre as the position of the fibre relative to the laser is altered. When the optimum alignment is achieved, the tube is secured in a fixed relationship to the laser. Using this approach requires that the package and the walls of the package do not deform due to changes in temperature, otherwise the fibre and the optical device could move out of optical alignment.
The cost of packaging optical devices is one of the key economic barriers to the deployment of a FTTH (fibre to the home) telecommunications network, since the devices are responsible for a significant proportion of the cost of the equipment to be installed in subscribers'premises. Of particular significance is the cost of optoelectronic components and assemblies such as, for example packaged semiconductor lasers. The largest component of the cost of, for example, a packaged semiconductor laser is incurred in the packaging of the device and not in the cost of the laser itself. One major cost for the packaging is for the special package or box required to house the laser and the hermetic sealing requirement associated with the package or box to protect the laser from the effects of humidity and other contaminants. Another contribution to the packaging cost is the need to use active fibre alignment techniques (i.e. techniques requiring active monitoring of laser light launched into the fibre during the alignment process) to align the optical
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Collins John Vincent
Fiddyment Philip John
Lealman Ian Francis
Payne Roger Alyn
Thurlow Adrian Richard
British Telecommunications public limited company
Palmer Phan T.H.
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