Multimode communications systems

• US 20020021469A1
• Filed: 08/20/2001
• Published: 02/21/2002
• Est. Priority Date: 05/13/1997
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Agilent Technologies, Inc.
• Inventors: Cunningham, David George, Coles, Alistair Neil, Musk, Robert William, Nowell, Mark Charles
• Granted Patent: US 6,609,834 B2
• Time in Patent Office: Days
• US Class Current: 398/139
• CPC Class Codes: H04B 10/2581 Multimode transmission

Abstract

A method and apparatus is provided for connecting an optical source to a multimode optical fibre in a multimode optical fibre communications system. A single mode fibre length is provided such that optical radiation admitted from an optical source at one end of the single mode fibre length is provided to a multimode optical fibre at the other end of the single mode fibre length. This method and apparatus is used in a duplex patchcord for connecting an optical transceiver to a pair of installed multimode fibres. The second fibre in the patchcord is a multimode fibre for passing optical signals to the optical receiver of the transceiver.

Claims

1. Apparatus for connecting an optical transceiver to multimode optical fibre in a multimode optical fibre communications system, the apparatus comprising:

a transmission part adapted for receiving outgoing optical radiation admitted to the apparatus from an optical source of the optical transceiver at a radiation input into a single mode optical fibre of the transmission part and adapted for transmitting said outgoing radiation out into a first multimode optical fibre of the multimode optical fibre communications system after passage through the single mode optical fibre, and;

a reception part adapted for receiving incoming optical radiation admitted to the apparatus from a second multimode optical fibre of the communications system into a multimode optical fibre of the reception part and adapted for transmitting said incoming radiation into a receiver of the optical transceiver.

2. Apparatus as claimed in claim 1, wherein the optical source of the optical transceiver is a laser.

3. Apparatus as claimed in claim 2, wherein outgoing optical radiation is transmitted directly from the single mode optical fibre into the first multimode optical fibre of the multimode optical fibre communications system.

4. Apparatus as claimed in claim 2, wherein a mode conditioning means is provided in the transmission part such that chosen modes of the multimode fibre will be preferentially excited by the outgoing radiation so as to increase the operational bandwidth of the first multimode optical fibre of the communications system.

5. Apparatus as claimed in claim 4, wherein said mode conditioning means comprises means to launch the outgoing radiation from the single mode fibre into a launch multimode fibre, such that the outgoing radiation illuminates an end face of the launch multimode fibre away from the axis of the launch multimode fibre.

6. Apparatus as claimed in claim 5, wherein said launch multimode fibre is the first multimode fibre of the multimode fibre communications system.

7. Apparatus as claimed in claim 5, wherein said launch multimode fibre is comprised within the transmission part.

8. Apparatus as claimed in claim 7, wherein the single mode fibre has an internal termination at a first ferrule and and the launch multimode fibre has an internal termination at a second ferrule, wherein the illumination of the end face of the launch multimode fibre away from the axis of the launch multimode fibre is achieved by an offset of the second ferrule from the first ferrule.

9. Apparatus as claimed in claim 8, wherein the second ferrule and the first ferrule are coaxial, wherein the single mode fibre and the launch multimode fibre are each mounted within the first ferrule and the second ferrule respectively such that the axis of each fibre is offset from the axis of the ferrule, and wherein the first ferrule is rotationally offset from the second ferrule such that the single mode fibre is offset from the launch multimode fibre.

10. Apparatus as claimed in claim 1, wherein the multimode optical fibre of the reception part has a core size greater than or equal to the core size of the second multimode fibre.

11. Apparatus as claimed in claim 1, further comprising distinguishing means to distinguish connections to the transmission part from connections to the reception part, such that connection between the optical source and the first multimode fibre can only be provided by the transmission part and connection between the optical receiver and the second multimode fibre can only be provided by the reception part.

12. Apparatus as claimed in claim 11, wherein the distinguishing means is provided by a keying mechanism at each end of the transmission and reception parts.

13. Apparatus as claimed in claim 1, wherein the apparatus is provided in the form of a patchcord.

14. Apparatus as claimed in claim 1, wherein the apparatus is provided in the form of a dongle.

15. Apparatus as claimed in claim 1, wherein the transmission part is adapted such that light admitted to the apparatus at the radiation input is provided as substantially single mode light after transmission through the single mode optical fibre of the transmission part.

17. Communications device as claimed in claim 16 wherein the optical source is a laser.

18. Communications device as claimed in claim 17, wherein outgoing optical radiation is transmitted directly from the single mode optical fibre into the first multimode optical fibre of the multimode optical fibre communications system.

19. Communications device as claimed in claim 17, wherein a mode conditioning means is provided in the transmission part such that chosen modes of the multimode fibre will be preferentially excited by the outgoing radiation so as to increase the operational bandwidth of the first multimode optical fibre of the communications system.

20. Communications device as claimed in claim 19, wherein said mode conditioning means comprises means to launch the outgoing radiation from the single mode fibre into a launch multimode fibre, such that the outgoing radiation illuminates an end face of the launch multimode fibre away from the axis of the launch multimode fibre.

21. Communications device as claimed in claim 20, wherein said launch multimode fibre is the first multimode fibre of the multimode fibre communications system.

22. Communications device as claimed in claim 20, wherein said launch multimode fibre is comprised within the transmission part.

23. Communications device as claimed in claim 22, wherein the single mode fibre has an internal termination at a first ferrule and and the launch multimode fibre has an internal termination at a second ferrule, wherein the illumination of the end face of the launch multimode fibre away from the axis of the launch multimode fibre is achieved by an offset of the second ferrule from the first ferrule.

24. Communications device as claimed in claim 23, wherein the second ferrule and the first ferrule are coaxial, wherein the single mode fibre and the launch multimode fibre are each mounted within the first ferrule and the second ferrule respectively such that the axis of each fibre is offset from the axis of the ferrule, and wherein the first ferrule is rotationally offset from the second ferrule such that the single mode fibre is offset from the launch multimode fibre.

25. Communications device as claimed in claim 16, wherein the transmission part is adapted such that light admitted to the apparatus at the radiation input is provided as substantially single mode light after transmission through the single mode optical fibre of the transmission part.

27. Communications system as claimed in claim 26, wherein the optical source is a laser.

28. Communications system as claimed in claim 27, wherein outgoing optical radiation is transmitted directly from the single mode optical fibre into the first multimode optical fibre.

29. Communications system as claimed in claim 27, wherein a mode conditioning means is provided in the transmission part such that chosen modes of the first multimode fibre will be preferentially excited by the outgoing radiation so as to increase the operational bandwidth of the communications system.

30. Communications system as claimed in claim 29, wherein said mode conditioning means comprises means to launch the outgoing radiation from the single mode fibre into a launch multimode fibre, such that the outgoing radiation illuminates an end face of the launch multimode fibre away from the axis of the launch multimode fibre.

31. Communications system as claimed in claim 30, wherein said launch multimode fibre is the first multimode fibre.

32. Communications system as claimed in claim 30, wherein said launch multimode fibre is comprised within the transmission part.

33. Communications system as claimed in claim 32, wherein the single mode fibre has an internal termination at a first ferrule and and the launch multimode fibre has an internal termination at a second ferrule, wherein the illumination of the end face of the launch multimode fibre away from the axis of the launch multimode fibre is achieved by an offset of the second ferrule from the first ferrule.

34. Communications system as claimed in claim 33, wherein the second ferrule and the first ferrule are coaxial, wherein the single mode fibre and the launch multimode fibre are each mounted within the first ferrule and the second ferrule respectively such that the axis of each fibre is offset from the axis of the ferrule, and wherein the first ferrule is rotationally offset from the second ferrule such that the single mode fibre is offset from the launch multimode fibre.

35. Communications system as claimed in claim 26, wherein distinguishing means are provided to ensure optical connection of the optical source to the first multimode optical fibre through the transmission part, and to ensure optical connection of the optical receiver to the second multimode optical fibre through the reception part.

36. Communications system as claimed in claim 35, wherein said distinguishing means are keys to determine relative spatial orientiations of the optical transceiver and the apparatus, and the apparatus and the first and second multimode optical fibres, respectively, on connection.

37. Communications system as claimed in claim 26, wherein the transmission part is adapted such that light admitted to the apparatus at the radiation input is provided as substantially single mode light after transmission through the single mode optical fibre of the transmission part.

39. A method as claimed in claim 38, wherein the step of measuring an output property comprises measuring a coupled power ratio into the multimode fibre.

16. Communications device for use in an multimode fibre optical communications system, comprising an optical transceiver and an apparatus comprising:

a transmission part adapted for receiving outgoing optical radiation admitted to the apparatus from an optical source of the optical transceiver at a radiation input into a single mode optical fibre of the transmission part and adapted for transmitting said outgoing radiation out into a first multimode optical fibre of the multimode optical fibre communications system after passage through the single mode optical fibre, and;

a reception part adapted for receiving incoming optical radiation admitted to the apparatus from a second multimode optical fibre of the communications system into a multimode optical fibre of the reception part and adapted for transmitting said incoming radiation into a receiver of the optical transceiver.

26. Communications system comprising an optical transceiver and first and second multimode optical fibres for receiving outgoing optical radiation from and supplying incoming optical radiation to the optical transceiver respectively, the optical transceiver and the first and second multimode optical fibres being connected by a connecting apparatus, the connecting apparatus comprising:

a transmission part adapted for receiving outgoing optical radiation admitted to the connecting apparatus from an optical source of the optical transceiver at a radiation input into a single mode optical fibre of the transmission part and adapted for transmitting said outgoing radiation out into the first multimode optical fibre after passage through the single mode optical fibre, and;

a reception part adapted for receiving incoming optical radiation admitted to the connecting apparatus from the second multimode optical fibre into a multimode optical fibre of the reception part and adapted for transmitting said incoming radiation into a receiver of the optical transceiver.

38. A method of constructing a connection apparatus for connecting an optical transceiver to multimode optical fibre in a multimode optical fibre system, comprising:

providing a length of single mode fibre terminating in a first ferrule, and providing a length of multimode fibre terminating in a second ferrule,

wherein the wherein the second ferrule and the first ferrule are coaxial,

wherein the single mode fibre and the multimode fibre are each mounted within the first ferrule and the second ferrule respectively such that the axis of each fibre is offset from the axis of the ferrule;

rotating the first ferrule with respect to the second ferrule such that the single mode fibre is offset from the launch multimode fibre, measuring an output property of light from the multimode fibre, and fixing the first ferrule with respect to the second ferrule when a satisfactory value of the output property is achieved;

providing a further length of multimode fibre, and adding connectors to the fibres, such that a first fibre path comprising the length of single mode fibre and the length of multimode fibre is formed for connection between a source of an optical transceiver and a first fibre of a multimode fibre network, and such that a second fibre path comprising the further length of multimode fibre is formed for connection between a receiver of the optical transceiver and a second fibre of the multimode fibre network.

40. A method for connecting an optical transceiver to multimode optical fibre in a multimode optical fibre communications system, comprising connecting the optical transceiver to first and second multimode optical fibres of the multimode optical fibre communications system with a connecting apparatus comprising a transmission part adapted for receiving outgoing optical radiation admitted to the apparatus from an optical source of the optical transceiver at a radiation input into a single mode optical fibre of the transmission part and adapted for transmitting said outgoing radiation out into a first multimode optical fibre of the multimode optical fibre communications system after passage through the single mode optical fibre and a reception part adapted for receiving incoming optical radiation admitted to the apparatus from a second multimode optical fibre of the communications system into a multimode optical fibre of the reception part and adapted for transmitting said incoming radiation into a receiver of the optical transceiver,

wherein outgoing radiation is transmitted from an optical source of the optical transceiver through the transmission part of the connecting apparatus to a first multimode fibre of the multimode optical fibre communications system, and incoming radiation is transmitted from a second multimode optical fibre of the multimode optical fibre communications system through the reception part of the connecting apparatus to an optical receiver of the optical transceiver.