WO1998034143A1

WO1998034143A1 - Optical component assemblies

Info

Publication number: WO1998034143A1
Application number: PCT/GB1998/000306
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: GB9702127D0

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 comprises a socket mounted on a wall (31) of the second component package (19), the processing device (18) having a wave guide with its input end (40) aligned with the socket. 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 comprises an optical fibre (37) having one end (36) disposed to receive light emitted by the emitter (35) and having its other end held by the one connector part (30) adjacent the end thereof remote from the emitter, whereby on coupling together the one and other connector parts (30, 32), the other end of the fibre is juxtaposed and in optical communication with the input end (40) of the processing device wave guide.

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 externally 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 being 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 second component having the other part of the two-part connector which other part is in the form of a socket arranged to receive the one connector part, the processing device having a wave guide with an input end aligned with the socket, the first and second components being directly interengageable by inserting the one connector part into the socket of the second component, and the optical path defining means of the first component comprising a optical fibre having its one end disposed to receive light emitted by the optical emitter and having its other end held by the one connector part adjacent the end of the one connector part remote from the emitter device, whereby on coupling the one and other connector parts, said other end of the fibre of the one connector part is juxtaposed and in optical communication with the input end of the wave guide of the processing device.

In 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. The optical signal from the first component is carried by an optical fibre extending through the one connector part and the package of the second component is arranged to provide a socket for that one connector part in such a way that the fibre of the one connector part may optically communicate directly with the wave guide of the processing device within the package of the second component. No external optical connection has to be made on coupling the two components. As there is only one optical connection to be made on completing the coupling of the first and second components the losses inevitably associated with an optical connection are reduced, leading to a greater efficiency of connection.

It is important that the socket of the second component is able to hold the one connector part of the first component in accurate alignment with the processing device, in order that the fibre of the first component may properly communicate with the wave guide of the processing device. Thus, the two parts of the connector must be manufactured to very tight dimensional tolerances, with high rigidities, bearing in mind that the core diameter of a typical single-mode optical fibre is in the range of 8-10 μm and the mode size of the wave guide may also be of the same order of magnitude. A coupling efficiency of at least 30% is typically required, in order to achieve satisfactory operation of an optical system. The package of the second component may be manufactured directly to provide the socket into which the one connector part of the first component is inserted. Preferably, though the socket is defined by an other connector part manufactured separately and connected to the package. Then, during manufacture of the second component, the installation of the processing device is performed with active alignment of its wave guide with the axis of the socket along which the optical fibre of the first component is to lie.

The optical emitter may comprise a laser device, said one end of the fibre of the first component is juxtaposed to the laser device so as directly to receive emitted light from the laser device. The collection of light from a semi-conductor laser in this way is understood in the art and typically -10 to 20 dB of the emitter power can be coupled to the fibre in this way. Alternatively, a lens train ma be arranged to collect light from the emitter and to direct that light into the fibre. In this case, optical correction may be applied by the lens train - for example, in a case of a semi-conductor laser, the optical signal may have an elliptical cross section and the lens train may include a circularising lens to convert the optical signal so as to have a substantially circular cross-section.

The other end of the fibre of the first component advantageously is held in a ferrule disposed co-axially within the outer end portion of the one connector part. In a mannerknown in the art, the end of the fibre, at the end of the ferrule, should be properly terminated for direct engagement with the input end of the wave guide of the processing device, upon inserting the one connector part into the socket of the second component. 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 socket aligned with the output end of the wave guide of the processing device, whereby a further one connector part may be inserted into said further socket. In this way, the fibre of the further connector part will be in optical communication with the output end of the wave guide. The fibre of the further one connector part may be a network fibre to which the modulator is to connect, or the further one connector part could be provided on a further optical component. In the latter case, 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 configured to provide the other part 32 of the connector. The one part 30 is generally of male form and the other part 32 is in the form of a socket which may receive the one part 30, both parts of the connector are manufactured with very high dimensional accuracies whereby the position of the free end of the one connector part, when inserted in the socket, may be assured to within a few μm.

Figure 3 shows diagrammatically a laser device 35 mounted within the package 11 , but not the electrical connections thereto from the leads 13. Light emitted from the laser device 35 is directed into end face 36 of a fibre 37 held within the package 11. The end portion of the fibre 37 may be disposed within a ferrule (not shown) held in a suitable manner within the package but as the light emitted by the laser is divergent, the end face of the fibre does not need to be positioned with great accuracy in order to collect a significant quantity of light from the laser. The other end portion 38 of the fibre 37 is held within a ferrule 39 located in the free end of the one connector part 30, with the end faces of the fibre and the ferrule proud of the end face of the one connector part The fibre and the ferrule end faces are finished in a manner known in the art, for completing a connection to an optical component or second fibre

Though not shown in the drawings, a lens or lens train may be positioned between the laser device 35 and the end face 36 of the fibre 37, in order to increase the emitter power directed into the fibre 37 In addition, correcting lenses may be employed, for example to convert the generally elliptical cross-section of the light emitted by the laser to a more circular form

The mounting of the modulator 18 within the package 19 of the second component is such that the input end of a wave guide (not shown) at end face

40 of the modulator is accurately aligned with the axis of fibre 37, when the one connector part is inserted in the socket For convenience during manufacture, this may be achieved by providing a dummy one connector part including a fibre along which light is directed, the positioning of the modulator being determined by optimising the optical coupling of its wave guide to the fibre of the dummy connector part

The optical modulator 18 together with its package 19 is provided with a further socket in order to take the modulated optical signal out of the package and to some other component or fibre This further socket is of the same construction as the first mentioned socket at the input end of the wave guide, to allow the insertion of a further one connector part mounted at the free end of a fibre (as shown in Figure 3) or provided on some other component In the latter 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 having a laser device emitting light into fibre 37 This invention is not limited to the first component having 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 one connector part and its socket may include interfitting lugs and recesses or other means whereby the one connector part may be coupled only in a fixed and predefined rotational alignment with the socket. 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 being 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 second component having the other part of the two-part connector which other part is in the form of a socket arranged to receive the one connector part, the processing device having a wave guide with an input end aligned with the socket, the first and second components being directly interengageable by inserting^" the one connector part into the socket of the second component, and the optical path defining means of the first component comprising a optical fibre having its one end disposed to receive light emitted by the optical emitter and having its other end held by the one connector part adjacent the -end of the one connector part remote from the emitter device, whereby on coupling the one and other connector parts, said other end of the fibre of the one connector part is juxtaposed and in optical communication with the input end of the wave guide of the processing device.

2. An assembly as claimed in claim 1 , wherein the optical emitter comprises a laser device and said one end of the fibre of the first component is juxtaposed to the laser device so as directly to receive emitted light from the laser device.

3. An assembly a┬º claimed in claim 1 , wherein the optical emitter comprises a laser device, a lens train being arranged to collect emitted light and direct that light into said one end of the fibre of the first component.

4. An assembly as claimed in any of the preceding claims, wherein said other end of the fibre of the first component is held in a ferrule disposed co-axially within the outer end portion of the one connector part.

5. An assembly as claimed in claim 4, wherein the ferrule of the one connector part directly engages the processing device of the second component with the fibre of the first component in direct abutting engagement with the input end of the wave guide of the processing device.

6. 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.

7. An assembly as claimed in any of the preceding claims, wherein the wave guide of the processing device has an output end and the second component defines a further socket aligned with said output end, whereby a further one connector part may be inserted into said further socket so that the fibre of the further connector part is in optical communication with the output end of the processing device.