GB2386432A

GB2386432A - Sealed optic fibre package containing optics chip

Info

Publication number: GB2386432A
Application number: GB0205655A
Authority: GB
Inventors: Steven Graham Batsford; Darren Lee Martin
Original assignee: Bookham Technology PLC
Current assignee: Lumentum Technology UK Ltd
Priority date: 2002-03-11
Filing date: 2002-03-11
Publication date: 2003-09-17
Also published as: WO2003079086A1; GB0205655D0; AU2003209478A1

Abstract

A method of assembling an optics package comprises: stripping a selected portion of one or more optic fibres 32 of their protective claddings; securing the one or more optic fibres to an optics chip 8; providing upper 22 and lower portions 20 of the package, said lower package portion having an extending part 26; locating the one or more optical fibres on the extending part such that the stripped portion of each fibre is located between the upper and lower package portions; and hermetically sealing the upper package portion to the lower package portion about the stripped portion of each fibre. Glass seal 34 and epoxy 36 are shown.

Description

AN OPTICS PACKAGE AND METHOD OF ASSEMBLING SAME

The present invention relates to an optics package and a method of assembling an optics package.

An existing optics package is illustrated in Figure 1. The package comprises an outer casing which has a lower portion 2 consisting of a base and sidewalls defining an interior and a lid 4 which covers the interior and which is sealed at its edges to the lower portion 2. This sealing is by way of soldering, brazing or welding. The package contains an optics chip 8 which contains a plurality of integrated optoelectronics devices. It will be appreciated that the package could house a single device such as a laser or photodiode. To these devices are connected a plurality of optical fibres 10 which are provided in the form of a coated ribbon fibre 12 the coating of which is partially stripped prior to attachment of the optical fibres 10 to the optics chip 8.

The ends of the optical fibres 10 are secured to the optics chip 8 (or fibre block, laser, photodiode etc.) by epoxy welding or other attach method, and the ribbon fibre 12 itself holds the optic fibres 10 in place due to the fact that it is held by the solder 6 which secures the lid 4 to the lower portion 2 of the package.

This form of package does not give a hermetic seal. Figure 1A illustrates an alternative package which provides a hermetic seal. The package is denoted by reference numeral 2' and is in the form of a hermetically sealed casing from which extends an integral tubular portion 3. An optics chip 8 is located within the package and is secured to an optical fibre 10. The optical fibre is guided by a ferrule 5 which is secured to the tube 3 by a solder seal 7.

It is difficult to provide in this type of package accommodation for a multi-fibre ribbon.

According to one aspect of the invention there is provided an optics package comprising: a lower portion defining a base of a package and having a frontwardly extending part; an upper portion secured to the lower casing portion, the upper and lower portions defining a package interior; at least one optical fibre location on the extending part and extending into the package interior where it is connected to an optics chip; and a seal formed around the point of entry of said at least one optical fibre into the package interior.

According to another aspect of the invention there is provided an optics package comprising a lower casing portion defining an interior of the package and having a front wall from which extends a shelf, a lid portion secured to the lower casing portion to cover the interior; at least one optical fibre located on the shelf and extending into the interior of the package where it is connected to an optics chip; and a seal formed around the point of entry of said at least one optical fibre into the interior of the package.

In the described embodiment, the shelf extends to the exterior of the package.

However it will be appreciated that the shelf could also extend to the interior of the package. In the preferred embodiment, the seal is a glass seal which is produced by heating a glass preform located at the point of entry of the optical fibre into the interior of the package.

Another aspect of the invention provides a method of assembling an optics package, the method comprising: securing at least one optical fibre to an optics chip; providing a lower portion of the package, said lower portion having an extending part and locating said at least one optical fibre on said extending part; sealing an upper portion to the lower portion; and providing a seal at the point of entry of the optical fibre into the package.

The optical fibre can be secured to the chip before or after the step of locating the optical chip into the package.

For a better understanding of the present invention and to show how the same may be carried into effect, reference will now be made by way of example to the accompanying drawings, in which: Figures 1 and 1A are schematic diagrams of existing optics packages; Figure 2 is a schematic perspective diagram of an optics package in accordance with one embodiment of the invention; Figure 3 is a section taken along the line lil-lil in Figure 2; Figure 3A is a section taken along the line lil-lil of an alternative embodiment similar to that of Figure 2; Figure 3B is a section taken along the line lil-lil of a further embodiment similar to that illustrated in Figure 2; Figure 4 is a schematic exploded diagram illustrating how the package of Figures 2 and 3 is assembled; and Figure 5 illustrates an alternative embodiment.

Figure 2 illustrates in a schematic perspective an improved optics package in accordance with one embodiment of the invention. That package comprises a lower casing portion 20 and a lid 22. The lid 22 is secured to the lower casing portion 20 by soldering, welding or brazing 24 but the overall method of assembly is different as discussed in more detail in the following. The lower portion 20 of the casing has a front wall from which protrudes a shelf 26 provided with a recess 28 which extends the length of the shelf 26. The shelf 26 extends to the exterior of the package approximately perpendicularly to the front wall of the lower casing portion 20. A ribbon fibre 30 having a plurality of optical fibres 32 is located in the recess 28 of the shelf 26. The cladding 30 of the ribbon fibre has been stripped to reveal an exposed portion of the optical fibres 32 prior to their entry into the interior of the package. These exposed optical fibres 32 are located in the recess

28 of the shelf 26. A glass seal 34 seals the optical fibres 32 at their point of entry into the interior of the package.

This is shown in more detail in the sectional view of Figure 3. Figure 3 also illustrates the integrated optics chip 8 in the interior of the package to which the optical fibres 32 are secured by epoxy 36. Thus, the shelf 26 can be seen supporting the ribbon fibre 30 and the exposed optical fibres 32 which extend through the glass seal 34 into the interior of the package.

Figure 3A illustrates an alternative embodiment, as though viewed along the section line 111-111 of Figure 2. In this embodiment, the optical fibre 32 retains an inner portion of cladding 30' in addition to its external portion 30. Epoxy resin 36', 36" is used to secure the cladding portion to the shelf 26. The inner cladding portion 30' abuts a fibre block or similar device which is used to connect the optical fibre 32 to the optical chip 8.

Figure 4 is an exploded view illustrating how the package is assembled. The lower casing portion 20 is provided first and the optics chip 8 located in its interior, supported in a known fashion. Of course, the package could contain multiple optics chips or chips of other kinds in a manner known per se. A ribbon fibre 30 is partially stripped to reveal exposed optical fibres 32 and the partially stripped ribbon fibre 30 is then laid in the recess 28 of the shelf 26. The ends of the optical fibres 32 are located in their proper location on the chip 8 in a manner known per se and tied off using epoxy resin 36, welding etc. Note that it would be possible to secure the exposed optical fibres 32 to the optics chip 8 prior to laying the ribbon fibre 30 on the shelf 26.

After this, the lid 22 is seam-sealed onto the lower casing portion 20 using standard techniques involving solder, weld or braze. This is denoted diagrammatically by the down arrows A in Figure 4. The part is then processed through a desiccation bake and then moved into a controlled dry environment ready for the glass sealing. To achieve the sealing step, a glass preform 33 is

placed onto the fibres as denoted by the arrow B in Figure 4. The preform is of low melting point glass. The part is then loaded into a heating station and a glass sealing station is used to heat the area to be sealed. In the sealing station, electrodes are used to pass a high current through the part or rf heating or other method to heat a localised area to in excess of 320 C so as to flow the glass.

After cooling, the part is removed from the station. The part is then gross and fine leak tested using standard equipment.

The electrode may be placed on the top, or at both the top and bottom of the package. As illustrated in Figure 3B, it is also possible to have a shelf with a hole 27 to allow for easier electrode access.

It will be appreciated that the method described with reference to Figure 4 may be modified slightly to take into account the constructional differences in the embodiment illustrated in Figure 3A.

Figure 5 illustrates an alternative embodiment of the invention where like parts as in the earlier described embodiments are denoted by like numerals but primed.

That is, the package comprises a lower portion 20' constituting a base for the package and an upper portion 22' constituting a lid. Differing from the earlier described embodiments, the lower portion 20' is flat whereas the upper portion 22' comprises a top wall and side wall. The side wall of the top portion is shaped to provide a flange. As before reference numeral 8 denotes an optical chip located on the package base. The lower portion 20' has a frontwardly extending part 26' which takes the place of the shelf described in the preceding embodiment. The extending part incorporates a recess 28' which serves the same function as in the earlier embodiments.

In other respects, construction of the package including location of the optical fibres within the recess 28', sealing of the upper portion 22' to the lower portion 20', and formation of a glass seal (not shown in Figure 5) are as for the earlier described embodiments.

It is to be noted that, in the place of the recess 28' in the extending part 26', it would be possible to incorporate a recess 25' in the flange portion 23 of the upper portion 22'.

Claims

CLAIMS:

1. An optics package comprising: a lower portion defining a base of a package and having a frontwardly extending part; an upper portion secured to the lower casing portion, the upper and lower portions defining a package interior; at least one optical fibre location on the extending part and extending into the package interior where it is connected to an optics chip; and a seal formed around the point of entry of said at least one optical fibre into the package interior.

2. An optics package according to claim 1, wherein the seal is a glass seal.

3. An optics package according to claim 1 or 2, wherein the upper portion is welded to the lower portion.

4. An optics package according to any preceding claim, in which there are a plurality of optical fibres provided in a common ribbon casing located on the extending part.

5. An optics package according to any preceding claim, wherein the extending part has a recess in which said at least one optical fibre is located.

6. An optics package according to any of claims 1 to 4, wherein the upper portion has a recess defined in its edge to accommodate said at least one optical fibre on the extending part.

7. An optics package comprising: a lower casing portion defining an interior of the package and having a front wall from which extends a shelf; a lid portion secured to the lower casing portion to cover the interior;

at least one optical fibre located on the shelf and extending into the interior of the package where it is connected to an optics chip; and a seal formed around the point of entry of said at least one optical fibre into the interior of the package.

8. A method of assembling an optics package, the method comprising: securing at least one optical fibre to an optics chip; providing a lower portion of the package, said lower portion having an extending part and locating said at least one optical fibre on said extending part; sealing an upper portion to the lower portion; and providing a seal at the point of entry of the optical fibre into the package.

9. A method according to claim 8, wherein the step of providing a seal is provided by heating a glass preform located at said point of entry.

10. A method according to claim 8 or 9, wherein the step of securing the optical fibre to the optics chip is carried out before locating the optical chip in the package.

11. A method according to claim 8 or 9, wherein the step of securing the optical fibre to the optics chip is carried out after locating the optical fibre chip in the package.

12. A method according to claim 9, wherein the step of heating the glass is carried out by connecting electrodes to the package and passing an electric current through the electrodes to thereby locally heat the area in which the glass preform is located.