WO1998034147A1

WO1998034147A1 - Optical component assemblies

Info

Publication number: WO1998034147A1
Application number: PCT/GB1998/000317
Authority: WO
Inventors: Adrian Charles O'donnell
Original assignee: Integrated Optical Components Limited
Priority date: 1997-02-03
Filing date: 1998-02-02
Publication date: 1998-08-06
Also published as: GB9702126D0

Abstract

An assembly of first and second optical components, the first component comprising a package (11) within which is contained an optical emitter (35) and the second component comprising a package (19) within which is contained an optical processing device (18). One part (30) of a two-part connector is mounted on a wall (16) of the first component package (11) and includes means defining an optical path coupled to the emitter (35). The other part (32) of the two-part connector is mounted on a wall (31) of the second component package (19) and includes means defining an optical path coupled to the processing device (18). The first and second components are directly interengageable by connecting together the two parts (30, 32) of the connector. The optical path defining means of the first component includes a beam expander (36) which receives an optical signal from the emitter (35) and the optical path defining means of the second component includes a lens (38) which focuses a received expanded beam directly into a wave guide of the processing device (18).

Description

OPTICAL COMPONENT ASSEMBLIES

This invention relates to an assembly of first and second optical components. Optical communications systems are being used increasingly for telecommunications and data transfer systems. Though widely used at present for long-haul systems, optical fibres are now being used for computer, local area and metropolitan networks. There is thus pressure for the manufacture of assemblies used in these networks to be simplified, resulting in lower costs, and also for increased component packing densities on network cards. Though many of the components used in a network card assembly may be positioned and connected to the card by automatic machinery, the handling of optical fibres on an automatic basis has proved to be extremely difficult. Many active and passive optical components comprise a device contained within an hermetically sealed package, with an optical fibre passing through the package wall and optically coupled to the device within the package. The fibre is sealed to the package wall where the fibre passes therethrough and a suitable length of the fibre (a so-called "pigtail") extends away from the package, for connection as required for example to a corresponding pigtail of some other component, to a connector on the card which is to carry the component, or the like. When the pigtail is to be connected to another fibre (such as the pigtail of another component), this may be done by fusing together the ends of the two fibres. An alternative technique, now being used more widely, is to provide an industry standard connector on the end of the pigtail, and to join that connector through a suitable adapter or uniter to a like connector provided on the free end of the other fibre. In either case, for many applications it is important to ensure the polarisation axes of the two fibres being joined are properly aligned, and this requires a high degree of rotational accuracy through the fibre join. Whichever technique is employed to join the pigtail to another fibre, the manufacture of a card assembly using optical components for use in a network installation requires management of the pigtails. Free areas must be provided on the card for the handling of the fibres, which areas may carry fibre management trays or use other techniques to ensure the fibres are controlled. In some cases, the area of a card required to accommodate the fibre management techniques can reach 50% of the total card area.

Considerable research effort has been expended in attempting to reduce the difficulties of managing the fibres extending between optical components mounted on a card. For example, connector designs have been proposed which are more reliable and have lower insertion losses, and which may permit the use of shorter pigtails. Despite this, there has been no satisfactory solution to the problem of significantly reducing the length or even eliminating the use of optical fibres for interconnecting optical components for mounting on a card, to produce an optical component assembly.

The present invention aims at providing an assembly of first and second optical components which eliminates the need for a fibre extending between the components and yet allows low coupling losses on the transfer of an optical signal from the first component to the second component.

According to the present invention, there is provided an assembly of first and second optical components, the first component comprising a package within which is contained an optical emitter device, one part of a two-part connector mounted on a wall portion of the package and having means defining an optical path therethrough which means is optically coupled to the emitter device, and the second component comprising a package within which is contained an optical processing device, the other part of the two-part connector mounted on a wall portion of the package and having means defining an optical path therethrough which means is optically coupled to the processing device, the first and second components being directly interengageable by connecting together the two parts of the connector, and the optical path defining means of the first component comprising a beam expander arranged to receive an optical signal from the emitter device, and the optical path defining means of the second component including a lens to receive the expanded beam from the connected first component which lens focuses the beam directly into a wave guide of the processing device.

According to a modified form of the invention, there is provided an assembly of first and second optical components, the first component comprising a package within which is contained an optical emitter device, one part of a two-part connector mounted on a wall portion of the package and having means defining an optical path therethrough which means is optically coupled to the emitter device, and the second component comprising a package within which is contained an optical processing device, a further one part of the two-part connector mounted on a wall portion of the package and having means defining an optical path therethrough which means is optically coupled to the processing device, the first and second components being interengageable by means of an adapter defining two other connector parts and with which the two one connector parts may couple, and the optical path defining means of the first component comprising a beam expander arranged to receive an optical signal from the emitter device, and the optical path defining means of the second component including a lens to receive the expanded beam from the connected first component which lens focuses the beam directly into a wave guide of the processing device.

In one form of the assembly of this invention, the first optical component is directly connected to the second optical component by means of a two-part connector one part of which is arranged on the first component and the other part on the second component. In the modified form of the assembly, the first optical component is connected to the second optical component by means of an adapter which connects to both of the two one parts of the connector, respectively on the two components. Such an adapter is purely mechanical in function and does not itself participate in the optical coupling. The difficulties of aligning and abutting fibres at an optical connection therebetween are overcome by eliminating fibres in the vicinity of the connection itself. The optical signal from the emitter is expanded to form a relatively large diameter collimated beam (perhaps of about 100μm to 1000μm diameter) which passes through the two connector parts and, in the optical path of the second component, is focused directly into a wave guide of the processing device of the second component. Thus, any small misalignment in the two connector parts will be of little consequence, as compared to the overall diameter of the expanded beam passing through the two connector parts. Moreover, the assembly does not require two fibres to be tightly abutted in precise alignment, unlike the case where connectors are used to join together the pigtails of two separate components.

Preferably, the optical path defining means of the first component forms a substantially symmetrical collimated beam which passes through an aperture in the wall portion of the first component package. In order to allow hermetic sealing of the package, that aperture may have a window for example of a sapphire plate fitted thereto and through which the beam may pass.

The optical signal emitted from the device of the first component may pass through a lens train comprising a collimator and a circularising lens. In a case where the emitter device is a semi-conductor laser, the optical signal therefrom usually has an elliptical cross-section and thus the circularising lens should be arranged to convert the optical signal so as to have a substantially circular cross-section. The optical path defining means may also include other components such as a polarising element or an optical isolator.

The optical path defining means of the second component is arranged so that the lens in that path focuses the beam directly into the wave guide of the processing device. The lens may comprise a substantially spherical lens directly supported within the other connector part, with only the central part of that lens being used for focusing the beam.

In a preferred construction, the other connector part may extend through the wall portion of the second component and a portion of the other connector part, lying within the package of the second component is configured directly to communicate with the processing device. For example, said portion of the other connector part is configured to receive therewithin an end portion of the processing device with the optical axis of the end plane of the wave guide therein on the optical axis of the other connector part.

The processing device of the second component may itself emit an optical signal. For example, in a case where the processing device is a modulator, the processing of the optical signal comprises modulation, the modulated signal being emitted from the second component. In such a case, the second component may be provided with a further connector part of a two part connector and having means defining an optical path therethrough which means is optically coupled to the signal emitting part of the processing device. Thus, a series of components may simply be connected together by interengaging the connector parts of the various components. It is therefore possible to construct an assembly of components in a simple and compact manner, without using external optical fibres for the connections between the components. This increased connectivity simplifies the construction of an assembly and permits mechanical handling of the components. By way of example only, an assembly of first and second optical components arranged in accordance with this invention will now be described, reference being made to the accompanying drawings, in which:-

Figure 1 is a plan view of a conventional optical component connection technique; Figure 2 is a side view on the arrangement of Figure 1 ; and

Figure 3 is a plan view of the first and second components of this invention. Referring initially to Figures 1 and 2, there is shown a first optical component 10 in the form of a package 11 containing a laser device (not shown). The package is provided with a pair of mounting holes 12 allowing the package to be secured to the surface of a card (also not shown) and electrical connection leads 13 extend away from the package on both sides thereof, for connection to tracks provided on the card. An optical fibre 14 passes through an opening in an end wall 16 of the package and is appropriately coupled to the laser device within the package to receive light emitted by the laser device. The fibre is sealed to the package using conventional techniques well known to those skilled in the art and which form no part of the present invention; they will not therefore be described in further detail here. The free end of the fibre 14 (which fibre is conventionally referred to as a "pigtail") is fitted with an industry standard connector 17. Also shown in Figures 1 and 2 is an optical modulator 18 having a package 19 provided with suitable mountings to permit the package to be secured to the surface of a card. The modulator 18 has electrical connection leads 21 projecting therefrom, for connection to further tracks provided on the card. In a manner similar to that described above with reference to the first optical component, the modulator has input and output optical fibres 22 and 23 passing through the package 19 and connected within the package to the modulator device therewithin. The fibres are sealed to the package and their free ends terminate in industry standard connectors 24 and 25 respectively, all three connectors 17, 24 and 25 being of the same design.

Connector 17 of the laser component 10 is optically coupled to connector 24 of the modulator 18 by means of an adapter 26 which connects optically and mechanically with both connectors. In a similar way, connector 25 of the modulator is optically coupled to a network fibre 27 having a similar connector 28 on its free end, by means of a further adapter 29. Referring now to Figure 3, like parts with those described above are given like reference characters and will not be described again here. End wall 16 of the laser package 11 is provided with one part 30 of a two part connector, end wall 31 of the second component package 19 being provided with the other part 32 of the connector. The one and other parts 30 and 32 are formed complementarily, the one part being of male form and the other part of female form, so that the parts may be mated together in a closely interfitting manner. The connector parts are manufactured to very tight tolerances with high concentricity, to ensure accurate coupling. Figure 3 shows diagrammatically a laser device 35 mounted within package 11 , but not the electrical connections thereto from the leads 13. Light emitted from the laser device 35 is generally somewhat elliptical and passes along an optical path to the one connector part 30, there being a lens train 36 in that path to perform collimation of the beam and if required also circularisation thereof. The circularisation, if implemented, converts the elliptical output to allow a high coupling efficiency to be achieved to an optical element in the second optical component, as the circularisation increases the overlap integral between the laser output, transformed by the lenses to the mode profile of the optical element of the second component. Collimation is performed by a conventional lens and the circularisation by one or more further lenses which may include a plano-convex lens which magnifies in only one plane or an aspheric lens which provides non-equal magnification in two planes mutually at right angles.

In the above manner, there is provided an expanded beam interface which allows the production of a beam diameter typically in the region of 100μm to 1000μm. This significantly relaxes the alignment tolerances of the interconnection between the first and second components, thereby easing the implementation of the direct coupling of the components and also improving the temperature performance of the assembly. The optical train may include additional elements 37, such as an optical isolator and/or a polariser. The collimated output is fed through an aperture in the package wall 16 provided with a window for example of a sapphire plate (not shown), to allow the laser device to be hermetically sealed within the package. On the outside of the package, in register, with the window in the end wall 16, is attached for example by welding or soldering the one part 30 of the two-part connector.

The other connector part 32 of the second component is arranged to extend through the wall of the package 19 on which the connector part is mounted for example by soldering or welding. Within the package 19, the connector part is configured to receive a part of the modulator device 18. Both the other connector part and the modulator device are appropriately configured to allow the two parts to interfit closely with the device 18 accurately located by the other connector part and with the end face of a wave guide of the device 18 normal to, or at same defined angle, and on the axis of the optical axis of the other connector part, the end face being located at a predetermined position along the length of the other connector axis.

Mounted within the other part 32 of the connector is a substantially spherical lens 38, arranged to collect the collimated expanded beam passing through the one connector part and to focus that beam on to the end face of the wave guide of the modulator 18, within the other connector part 32. If hermetic sealing is required, this may be achieved by means of a window 39 provided within the other connector part 32, on either side of the spherical lens 38 but preferably on the one connector side of that lens in order to minimise refraction effects as the light passes therethrough. The optical modulator 18 together with its package 19 is provided with a further connector part in order to take the modulated optical signal out of the package and to some other component or fibre. This further connector part is of the same construction as the other connector part 32 of the component. Alternatively, the further connector part may be of the same design of the one connector part 30 of the first component 10. In this case, similar components may be connected serially so permitting the assembly of a number of components in a simple and rapid manner. In the foregoing, the first component 10 has been described as a laser. This invention is not limited to the first component being a laser: the first component could be some other form of optical emitter, such as the downstream end of a modulator from which an optical signal issues. Though not illustrated in Figure 3, the two connector parts may include interfitting lugs and recesses or other means whereby the two connector parts may be coupled only in a fixed and predefined rotational alignment. In this way, should the optical signal from the first component be polarised, the polarisation axes of the signal being passed through the connector will be maintained.

Claims

1. An assembly of first and second optical components, the first component comprising a package within which is contained an optical emitter device, one part of a two-part connector mounted on a wall portion of the package and having means defining an optical path therethrough which means is optically coupled to the emitter device, and the second component comprising a package within which is contained an optical processing device, the other part of the two-part connector mounted on a wall portion of the package and having means defining an optical path therethrough which means is optically coupled to the processing device, the first and second components being directly interengageable by connecting together the two parts of the connector, and the optical path defining means of the first component comprising a beam expander arranged to receive an optical signal from the emitter device, and the optical path defining means of the second component including a lens to receive the expanded beam from the connected first component which lens focuses the beam directly into a wave guide of the processing device.

2. An assembly of first and second optical components, the first component comprising a package within which is contained an optical emitter device, one part of a two-part connector mounted on a wall portion of the package and having means defining an optical path therethrough which means is optically coupled to the emitter device, and the second component comprising a package within which is contained an optical processing device, a further one part of the two-part connector mounted on a wall portion of the package and having means defining an optical path therethrough which means is optically coupled to the processing device, the first and second components being interengageable by means of an adapter defining two other connector parts and with which the two one connector parts may couple, and the optical path defining means of the first component comprising a beam expander arranged to receive an optical signal from the emitter device, and the optical path defining means of the second component including a lens to receive the expanded beam from the connected first component which lens focuses the beam directly into a wave guide of the processing device.

3. An assembly as claimed in claim 1 or claim 2, wherein the optical path defining means of the first component forms a substantially symmetrical collimated beam which passes through an aperture in the wall portion of the package.

4. An assembly as claimed in claim 3, wherein the optical path defining means of the first component includes a collimator arranged to receive the optical signal from the emitter device.

5. An assembly as claimed in claim 3 or claim 4, wherein the optical path defining means of the first component includes a circularising lens arrange to convert the optical signal from the first component so as to have substantially a circular cross-section.

6. An assembly as claimed in any of the preceding claims, wherein the optical path defining means of the first component includes an optical isolator.

7. An assembly as claimed in any of the preceding claims, wherein the optical path defining means of the first component includes a polarising element arranged to introduce a known polarisation to the optical signal.

8. An assembly as claimed in any of the preceding claims, wherein the optical path defining means of the first component includes a window mounted in an aperture in the wall portion of the package of the first component, in register with the one connector part, which window is sealed to the package and through which the expanded beam passes into the one connector part.

9. An assembly as claimed in claim 8, wherein the window comprises a substantially transparent sapphire plate.

10. An assembly as claimed in any of the preceding claims, wherein the focusing lens of the optical path defining means of the second component comprises a spherical lens directly supported within the other connector part of the second component.

11. An assembly as claimed in any of the preceding claims, wherein the other connector part extends through the wall portion of the second component and a portion of the other connector part within the package of the second component is configured directly to communicate with the processing device.

12. An assembly as claimed in claim 11 , wherein said portion of the other connector part is configured to receive therewithin end portion of the processing device with the optical axis of the end plane of the wave guide therein on the optical axis of the other connector part.

13. An assembly as claimed in claim 11 or claim 12, wherein a further connector part is provided at the output end of the processing device, which further connector part is of the same form as the other connector part at the input end of the processing device.

14. An assembly as claimed in any of the preceding claims, wherein the two parts of the two-part connector are provided with interengaging means adapted to hold the connected parts in a fixed pre-set rotational alignment.

15. An assembly as claimed in any of the preceding claims, wherein the optical emitter device comprises a laser.