Optical waveguides – With disengagable mechanical connector – Optical fiber to a nonfiber optical device connector
Patent
1993-02-25
1994-06-07
Gonzalez, Frank
Optical waveguides
With disengagable mechanical connector
Optical fiber to a nonfiber optical device connector
385 91, G02B 636
Patent
active
053197291
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
One of the most important stages in the manufacture of integrated optic devices is the interfacing of integrated optic devices such as waveguides to optical fibres. This might involve individual fibres or fibre arrays; for both cases, however, all the reported techniques to date rely upon the use of adhesives, epoxies or solders. These all have different physical properties (e.g. thermal expansion) to those of silica fibres, thereby affecting the long term stability of the interface.
SUMMARY OF THE INVENTION
According to the present invention there is provided a method of interfacing an optical fibre to a silica integrated optic device comprising the steps of machining a locating groove in a silica block, fixing a prepared length of the optical fibre in the locating groove, bringing the block and the device into juxtaposition and aligning the block and the device to provide maximum transmission of a signal from the fibre to the device and laser welding the block and the device together by producing a series of spaced welds on either side of the fibre optic/device interface.
There is further provided a fibre optic/device interface produced using the method above.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will now be described, by way of example, with reference to the accompanying drawings, in which;
FIGS. 1a-1e show diagrammatic representations of the various weld formats available;
FIG. 2 is a diagrammatic view of a laser welding arrangement;
FIG. 3 shows a schematic representation of a weld structure;
FIG. 4 shows a view of the preferred V-groove silica block design; and
FIG. 5 shows a view of a completed welded assembly.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
In accordance with the present invention the material similarity of all-silica waveguides or other devices and optical fibres is utilised to establish an epoxy-free fusion interfacing between optical fibres and integrated-optic devices by using laser welding techniques. This is uniquely applicable to all-silica integrated devices since they have virtually identical material properties to those of optical fibres. In order to produce a silica to silica weld, localised heating of the material is required to a temperature of approximately 2000.degree. C. This has been readily achieved using a CO.sub.2 laser.
There are several types of weld available e.g. butt, corner, lap, T and edge welds as shown diagrammatically in FIGS. 1a-1e. These may be subdivided further as each may be either continuous seam, pulsed seam or spot welded. For the present application, the butt or lap welds, FIGS. 1a or 1b, are most useful. The butt joint, FIG. 1a, must be seam welded since there is no overlap to spot weld, whereas the lap joint, FIG. 1b, may be spot or seam welded.
The spot weld requires a highly focused beam to penetrate the top substrate causing fusion of the two around the periphery of the beam. The seam weld requires a defocused beam to heat both substrates, such that fusion occurs at the molten interface. The joint may be welded along the length of an interface or at selected points along this interface.
The principle of the laser welding technique is as follows: two silica blocks 1, 2 containing the input and output single mode fibres 3, 4 in laser-cut V-grooves 5, 6 are aligned with the waveguide block and laser welds 8 are formed between the three blocks 1, 2, 7 along two interfaces 9, 10 as shown in FIG. 2.
The laser welding process consists of a number of small and closely spaced (0.5 mm) welds 8 (see FIG. 3) on either side of the fibre/waveguide interface 9, 10. Each weld takes about 0.5 seconds to produce using a slightly defocused CO.sub.2 laser beam. The waveguide 7 and fibre blocks 1, 2 are mounted on a 5-axis alignment stage (not shown) fixed to a computer controlled XY table (not shown) which enables accurate positioning of the target area with respect to the beam and also controls the firing of the laser. Once the fibre-waveguide alignment has been optimised, the entire welding process
REFERENCES:
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patent: 5210811 (1993-05-01), Avelange et al.
"Laser Welded Fibre Waveguide Interfacing", J. J. Allen, et al, Ninth Annual European Fibre Optic Communications and Local Area Network Conference, London, Jun. 19-21, 1991.
Allen James J.
Nourshargh Noorallah
Gonzalez Frank
GPT Limited
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