OPTICAL ASSEMBLY AND METHOD FOR ALIGNMENT THEREOF

Abstract: The present invention provides an improved optical assembly for use in an optical telecommunications system and an improved method for aligning the optical assembly. The assembly uses a pair of ball bearings 7, 8) to support an optical fibre (2) on a baseplate (9). The optical fibre is aligned with respect to an optical device (15) and then the first ball bearing is inserted and welded in place. The fibre alignment is then fine tuned and the second ball bearing is inserted and welded in place. Advantageously, the present invention provides a simpler and more accurate method of aligning an optical fibre to an optical device.

Description: OPTICAL ASSEMBLY AND METHOD FOR ALIGNMENT THEREOF The present invention relates to an optical assembly and a method for aligning the optical assembly. More specifically, the present invention relates to an optical assembly and method for aligning an optical fibre to an optical device for use within an optical telecommunications system. Current methods of aligning optical fibres to optical devices such as laser diodes and photo diodes are expensive and time consuming. In addition they do not provide the accuracy required for modern optical fibre applications such as is required in optical telecommunications systems. The present invention overcomes these technical problems by providing a simpler optical assembly and method for aligning and fixing the optical assembly. According to the present invention there is provided an optical assembly comprising an optical fibre mounted in a tube, a baseplate, and a support member fixedly disposed between said optical fibre and said baseplate. The assembly may further comprise a further support member fixedly disposed between said optical fibre and said baseplate. The support members are preferably ball bearings. The baseplate may include a groove in which the ball bearings are inserted and to which the ball bearings are subsequently fixed. According to a further aspect of the present invention, said optical fibre is disposed in a first mount means proximate to an optical device and to which said support member is fixed. The optical fibre may also be disposed in a second mount means distal from said optical device and to which said further support member is fixed. Preferably said first and second mount means include an angled surface to which said support members are fixed. Alternatively, the baseplate includes at least one angled area to which said support member is fixedly attached. According to yet a further aspect of the present invention, the optical assembly comprising an optical fibre mounted in a tube, a baseplate, said baseplate including a raised member fixedly disposed thereon, and an elongated arm inserted between said raised member and said tube. Preferably, the optical assembly according to the present invention is used in an optical telecommunications system. According to the present invention there is provided a method of aligning an optical fibre to an optical device comprising the steps of: pre-aligning the optical fibre to the optical device, inserting a support member between the optical fibre and a baseplate, fixing said support member to the optical fibre and to the baseplate, adjusting the alignment of the optical fibre to the optical device, inserting a further support member between the optical fibre and the baseplate, and fixing said further support member to the optical fibre and to the baseplate. Advantageously, the present invention maintains alignment of the optical fibre to the optical device after the supporting members have been fixed to the fibre or to the first and second fibre mounting means and to the baseplate. The method of fixing the ball bearings is preferably resistive welding. However, as will be appreciated, other suitable fixing means or methods could be used, such as laser welding. The optical assembly may include a lens disposed between the optical fibre and the optical device. As will be appreciated, the optical assembly may include other optical elements, such as an optical isolator. Advantageously, the present invention reduces or eliminates the need for tweaking the alignment of the optical fibre after fixing in order to re-establish maximum coupling efficiency between the optical fibre and the optical device. The present invention also reduces or eliminates the chances of movement of the optical fibre during the fixing or welding process. Advantageously, by using mount means with an angled surface all tolerances associated with the individual components of the optical assembly and their alignment with respect to each other are removed. Once fixing has taken place, the present invention provides a continuous joint in which there are no fixing or weld gaps. While the principle advantages and features of the invention have been described above, a greater understanding and appreciation of the invention may be obtained by referring to the drawings and detailed description of the preferred embodiments, presented by way of example only, in which; Figure 1 is a side view of the optical assembly according to a first embodiment of the present invention, Figure 2 is a side view of the optical assembly according to a second embodiment of the present invention, Figure 3 is an end view the optical assembly shown in either figures 1 or 2 and includes a groove in the baseplate, Figure 4 is a more detailed diagram of the optical assembly shown in figure 2, Figures 5 is a side view of the optical assembly according to a third embodiment of the present invention, Figure 6 is an end view of the optical assembly shown in figure 5, and Figure 7 shows yet a further alternative embodiment of the present invention. In figure 1 the optical assembly 1 is shown comprising an optical fibre 2 mounted in a fibre tube 3. One end of the optical fibre 4 is aligned to an optical device (not shown). The fibre tube has a mount means 5 disposed around the fibre. Support member 7 is disposed between the mount means 5 and a baseplate 9. In this embodiment the support member is preferably a ball bearing. The ball bearing is fixed to the mount member and baseplate, preferably by resistive welding. However, as will be appreciated other fixing methods can be used, such as laser welding. In figure 2, where parts also appearing in figure 1 bear identical numerical designation, the optical assembly 20 is shown comprising an optical fibre 2 mounted in a fibre tube 3. One end of the optical fibre 4 is aligned to an optical device (not shown). The fibre tube has a mount means 5 disposed proximate the optical device and a further mount means 6 disposed at the opposite end of the fibre tube. Support members 7 and 8 are disposed between the mount means 5 and 6 respectively and a baseplate 9. As in the previous embodiment, the support members are preferably ball bearings. The ball bearings are fixed to the mount members and baseplate, preferably by resistive welding. Accurate alignment of end 4 of the fibre to an optical device is achieved as follows. Rough alignment of end 4 of the fibre to the optical device is done using conventional micro alignment equipment. Then the first ball bearing 7 is inserted between the fibre mount means 5 and welded in place. Next accurate alignment of the fibre to the optical device is achieved by manipulating the distal end 10 of the fibre using conventional micropositioning equipment. As is known in the art, optimum alignment is determined by powering the optical device and monitoring the output from the distal end of the fibre. Once optimum alignment is detected, the second ball bearing 8 is inserted between the second mount means 6 and the baseplate 9 and welded in place. In figure 3, where parts also appearing in figures 1 and 2 bear identical numerical designation, baseplate 9 is shown comprising a groove 12. Advantageously, the groove allows for the ball bearings to be rolled into place prior to welding. In figure 4, in which parts also appearing in figures 1-3 bear identical numerical designation, an optical device 15 is located at end 4 of the optical fibre. As clearly seen in figure 4, the lower surfaces 25 and 26 of mount means 5 and 6 respectively are angled with respect to the baseplate. Angles 35, 36 enable the ball bearings 7, 8 to be rolled into place along the groove 12 and stop when contact is made with the mount means 5, 6. These angles enable a variety of alignment positions to be accommodated for using the same pieceparts. The presence of the angled lower surfaces on the mount means significantly improves the flexibility and ease of use of this present invention. Figures 5 and 6 show a further embodiment in which the baseplate 9 includes a raised member 20. The raised member may be part of the baseplate or a separate piecepart attached to the baseplate. Instead of ball bearings an elongated arm 21 is inserted between the raised member 20 and the fibre 2. As with the previously described embodiments, the elongated arm is welded in place after optimum alignment is achieved. In figure 7, where parts also appearing in the previous figures bear identical numerical designation, the optical assembly 70 has a baseplate 9 which is arranged to include angled portions 41, 42. These angled portions function in the same way as angles 35 and 36 shown in figure 4 above. However, instead of being located on the lower surface of mount means the angels are disposed in the baseplate. It is not intended that the present invention be limited to the above embodiments and other modifications and variations are envisaged within the scope of the claims.

Claims: Claims 1. An optical assembly comprising an optical fibre (2) mounted in a tube (3), a baseplate (9), and a support member (7) fixedly disposed between said fibre and said baseplate. 2. An optical assembly as claimed in Claim 1, further comprising a further support member (8) fixedly disposed between said fibre and said baseplate. 3. An optical assembly as claimed in Claim 2, wherein said support member (7) and/or said further support member (8) is a ball bearing. 4. An optical assembly as claimed in any preceding Claim, wherein said baseplate (9) includes a groove (12). 5. An optical assembly as claimed in any preceding Claim, wherein said optical fibre (2) is disposed in a first mount means (5) proximate to an optical device (15). 6. An optical assembly as claimed in Claim.5, wherein said optical fibre (2) is further disposed in a second mount means (6) distal to said optical device. 7. An optical assembly as claimed in Claim 5, wherein said first mount means (5) includes an angled surface (35) to which said support member (7) is fixed. An optical assembly as claimed in Claim 6, wherein said second mount means (6) includes an angled surface (36) to which said further support member (8) is fixed. 9. An optical assembly as claimed in any preceding Claim, wherein said baseplate includes at least one angled portion (41, 42) to which said support member (7, 8) is fixedly attached. 10. An optical assembly as claimed in any preceding Claim, wherein said optical device (15) is a laser. 11. An optical assembly comprising an optical fibre (2) mounted in a tube (3), a baseplate (9), said baseplate including a raised member (20) fixedly disposed thereon, and an elongated arm (21) inserted between said raised member and said tube. 12. An optical telecommunications system using an optical assembly as claimed in any preceding Claim. 13. A method of aligning an optical fibre (2) to an optical device (15) comprises the steps of: pre-aligning the optical fibre to the optical device, inserting a support member (7) between the optical fibre and a baseplate (9), fixing the support member to the optical fibre and to the baseplate, adjusting the alignment of the optical fibre to the optical device, inserting a further support member (8) between the optical fibre and the baseplate, and fixing said further support member to the optical fibre and to the baseplate.

Inventors: MEADOWCROFT SIMON, MEADOWCROFT, SIMON
Applicants: AGILENT TECHNOLOGIES INC, MEADOWCROFT SIMON, AGILENT TECHNOLOGIES, INC., MEADOWCROFT, SIMON
Application year: 2001
Main classification: G02B6
IPC codes: G02B6