METHOD AND DEVICE FOR TRANSMISSION OF OPTICAL DATA BETWEEN TRANSMITTER STATION AND RECEIVER STATION VIA OF A MULTI-MODE LIGHT WAVE GUIDE

• US 20120121220A1
• Filed: 06/14/2010
• Published: 05/17/2012
• Est. Priority Date: 06/13/2009
• Status: Active Grant

• Current Assignee: Technische Universitaet Dortmund
• Original Assignee: Technische Universitaet Dortmund
• Inventors: Krummrich, Peter
• Granted Patent: US 8,582,932 B2
• Time in Patent Office: Days
• US Class Current: 385/28
• CPC Class Codes: H04B 10/2581 Multimode transmission
• CPC Class Codes: H04J 14/02 Wavelength-division multiplex systems
• CPC Class Codes: H04J 14/04 Mode multiplex systems

Abstract

The invention relates to a method for transmitting optical information between an emitter station (7) and a receiving station (6) via a multi-mode optical wave guide (3) using a wave length multiplex method. According to the invention, several optical emitters (OS) generate a respective signal (TX) for each of the wave lengths to be transmitted, and the signals (TX) are fed to the multi-mode optical wave guide (3) in the form of a number of modes via mode multiplexers (MM) and wavelength multiplexers (WM), the multi-mode optical wave guide (3) having its own mode that can propagate within the multi-mode optical wave guide (3) for each of the modes to be transmitted and after the transmission and optionally the regeneration and/or amplification of the signal via the multi-mode optical wave guide (3), the transmitted signals are broken down via the wavelength multiplexer (WD) into groups of signals having the same wavelength and via the mode demultiplexer (MD) into signals having the same mode, and subsequently, the interference signals are extracted from the transmitted demultiplexed signals (RX), the interference signals being formed due to over coupling between the individual modes during the transmission via the multi-mode optical wave guide (3).

Claims

1. Method for transmission of optical data between a transmitter station (7) and a receiver station (6), by way of a multi-mode light waveguide (3), using a wavelength multiplex method,

wherein

multiple optical transmitters (OS) generate a signal (TX), in each instance, for each of the wavelengths to be transmitted, and these signals (TX) are applied, in the form of a plurality of modes, to the multi-mode light waveguide (3), by way of mode multiplexer(s) (MM) and wavelength multiplexer(s) (WM), wherein the multi-mode light waveguide (3) has a separate mode capable of propagation within the multi-mode light waveguide (3) for each of the modes to be transmitted,

after transmission and, if applicable, regeneration and/or amplification of the signal by way of the multi-mode light waveguide (3), the transmitted signals are split up into groups of signals having the same wavelength, by way of wavelength demultiplexer(s) (WD), and into signals having the same mode, by way of mode demultiplexer(s) (MD),

the interference signals that resulted from over-coupling between the individual modes during transmission by way of the multi-mode light waveguide (3) are removed from the transmitted demultiplexed signals (RX).

2. Method according to claim 1, wherein during multiplexing, the signals (TX) for each of the wavelengths to be transmitted are first applied to a number of mode multiplexers (MM) and subsequently to a common wavelength multiplexer (WM).

3. Method according to claim 2, wherein the signals (TX) are passed to the mode multiplexers (MM) in the basic mode of a single-mode light waveguide (1) or in the form of a free beam, in each instance, for multiplexing in the mode multiplexers (MM).

4. Method according to claim 3, wherein transformation of the field distributions takes place in the mode multiplexers (MM), during which each incoming signal (TX) excites a mode of the multi-mode light waveguide (3) disposed on the output side of the mode multiplexer (MM), in each instance.

5. Method according to claim 3, wherein at least as many modes are capable of propagation in the multi-mode light waveguides (3), between mode multiplexers (MM) and wavelength multiplexer (WM), as the number of signals (TX) to be transmitted between mode multiplexers (MM) and wavelength multiplexer (WM).

6. Method according to claim 5, wherein the multi-mode light waveguide (3) transmits the signals that have been multiplexed together and that all have the same wavelength, between mode multiplexers (MM) and wavelength multiplexer (WM).

7. Method according to claim 2, wherein all the signal groups at the different wavelengths are brought together in the wavelength multiplexer (WM), in a single multi-mode light waveguide (3), for transmission to the receiver station (6).

8. Method according to claim 1, wherein during multiplexing, the signals (TX) for each of the wavelengths to be transmitted are first applied to a wavelength multiplexer (WM) and subsequently to a common mode multiplexer (MM).

9. Method according to claim 8, wherein the signals (TX) are passed to the wavelength multiplexers in the basic mode of a single-mode light waveguide (1) or in the form of a free beam, in each instance, for multiplexing in the wavelength multiplexers (WM).

10. Method according to claim 9, excitation of the modes of a multi-mode light waveguide (3) by the wavelength groups generated by the wavelength multiplexers (WM), in each instance, takes place in the mode multiplexer (MM) that follows the wavelength multiplexers (WM).

11. Method according to claim 1, wherein during demultiplexing, the transmitted signals are first applied to a wavelength demultiplexer (WD) and subsequently to a number of mode demultiplexers (MD).

12. Method according to claim 11, wherein the wavelength demultiplexer (WD) separates the channel groups at the individual wavelengths, and passes a group of channels having the same wavelength, in each instance, to the mode demultiplexers (MD) by way of multi-mode light waveguides (4).

13. Method according to claim 11, wherein separation of the signals into the individual modes takes place in the mode demultiplexers (MD).

14. Method according to claim 1, wherein during demultiplexing, the transmitted signals are first applied to a mode demultiplexer (MD) and subsequently to a number of wavelength demultiplexers (WD).

15. Method according to claim 14, wherein separation of the signal groups into the individual modes takes place in the mode demultiplexer (MD).

16. Method according to claim 14, wherein the wavelength demultiplexers (WD) separate the signals at the individual wavelengths.

17. Method according to claim 1, wherein optical amplification and transmission of the signals takes place in multi-mode technology, by way of the multi-mode light waveguide (3), between transmitter station (7) and receiver station (6).

18. Method according to claim 1, wherein the multi-mode light waveguide (3) has an increased number of carried modes in a step light waveguide (3), by means of an increase in the core diameter and/or an increase in the index jump at the core/mantle boundary.

19. Method according to claim 1, wherein the multi-mode light waveguide (3) has an increased number of carried modes, as the result of an increase in the size of the fiber parameter V, in the case of index of refraction profiles having dissimilar shapes.

20. Method according to claim 1, wherein the method utilizes every mode of the multi-mode light waveguide (3) that is capable of propagation, between transmitter station (7) and receiver station (6), for transmission of a separate signal (TX) or channel, if applicable combined with polarization multiplex operation.

21. Device for transmission of optical data between a transmitter station (7) and a receiver station (6), by way of a multi-mode light waveguide (3), using a wavelength multiplex method, particularly for implementing the method according to claim 1,

wherein

the device has a transmitter station (7) having multiple optical transmitters (OS) for each of the wavelengths to be transmitted, which transmitters each produce a signal (TX) and apply these signals (TX) to the multi-mode light waveguide (3) by way of mode multiplexers (MM) and wavelength multiplexers (WM), wherein the multi-mode light waveguide (3) has a separate mode capable of propagation within the multi-mode light waveguide (3) for each of the modes to be transmitted,

the device has a receiver station (6) having multiple optical receivers (OE) that split the transmitted signals (RX) up into groups of signals having the same wavelength, by way of wavelength demultiplexers (WD), and into signals having the same mode, by way of mode demultiplexers (MD).

22. Device according to claim 21, wherein the transmitter station (7) has a mode multiplexer (MM), in each instance, for multiplexing the signals (TX) for each of the wavelengths or wavelength channels to be transmitted, and a common wavelength multiplexer (WM) that processes the output signals (TX′

) of the mode multiplexers (MM).

23. Device according to claim 21, wherein the transmitter station (7) has a wavelength multiplexer (WM) for multiplexing the signals (TX) for each of the wavelengths or wavelength channels, in each instance, and a common mode multiplexer (MM) that processes the output signals (TX′

) of the wavelength multiplexers (WM).

24. Device according to claim 21, wherein the receiver station (6) has a common wavelength demultiplexer (WD) for demultiplexing the signals (RX) for all the transmitted wavelengths or wavelength channels, and a number of mode demultiplexers (MD) that process the output signals (RX′

) of the wavelength demultiplexer (WD).

25. Device according to claim 21, wherein the receiver station (6) has a common mode demultiplexer (MD) for demultiplexing the signals (RX) for all the transmitted wavelengths or wavelength channels, and a number of wavelength demultiplexers (WD) that process the output signals (RX′

) of the mode demultiplexer (MD).

26. Device according to claim 21, wherein the mode multiplexer (MM) has a number of gradient lenses (GL_ein) on the input side that corresponds to the number of signal channels to be transmitted, which lenses convert the field distribution of the signals (TX) in the basic mode of single-mode light waveguides (1) into parallel beams, and wherein mode converters (MK) follow the gradient lenses (GL_ein), which convert the field distribution of the signals (TX) in such a manner that each signal, after they are brought together in semi-transparent mirrors (TS) and focused using a subsequent gradient lens (GL_aus), excites precisely one mode of the multi-mode light waveguide (2) disposed on the output side of the mode multiplexer (MM).

27. Device according to claim 26, wherein holograms or suitable spatial filters are present in the mode converters (MK), with which transformation of the field distribution takes place.

28. Device according to claim 21, wherein the mode multiplexer (MM) has a gradient lens (GL_ein) on the input side that transforms the output signal of the multi-mode waveguide (3) into a parallel beam, wherein semi-transparent mirrors (TS) follow the gradient lens (GL_ein), which multiply the parallel beam and pass it to mode converters (MK) that undertake transformation of the field distribution of the desired mode into a field distribution that excites the basic mode of the single-mode light waveguide (4) on the output side after focusing in a subsequent gradient lens (GL_aus).

29. Device according to claim 28, wherein the mode converters (MK) are configured in such a manner that they maintain the orthogonality of the field distributions.

30. Device according to claim 28, wherein the mode demultiplexer (MD) couples each mode of the multi-mode light waveguide (3) on the input side into precisely one single-mode light waveguide (4) on the output side, in each instance.

31. Device according to claim 28, wherein the mode demultiplexer (MD) is followed by a cross-mode interference canceller (XMIC), which undertakes separation of the interference components that occurred along the transmission segment (3), by means of mode coupling.

32. Device according to claim 31, wherein the cross-mode interference canceller (XMIC) uncouples part of the signal per input, multiplies it by a coefficient that influences the amount and the phase of the signal, and passes it to another output.

33. Device according to claim 28, wherein an electrical module follows the mode demultiplexer (MD), which removed the interference components from the demultiplexed signals after conversion to the electrical plane, wherein the output signals of the mode demultiplexer (MD) are coherently detected using superimposition receivers, and subsequently converted to digital signals.

34. Device according to claim 33, wherein means for digital signal processing are provided in the electrical module, which means perform cancellation of the interference components in accordance with the principle of the cross-mode interference canceller.

35. Device according to claim 21, wherein a waveguide arrangement for coherent detection is disposed behind the output (MM-LWL) of the multi-mode light waveguide (3), having a coupling zone (KZ), which arrangement makes a transition into a number of single-mode light waveguides (SM-LWL).

36. Device according to claim 35, wherein the number of outgoing single-mode light waveguides (SM-LWL) is selected in such a manner that at least one single-mode light waveguide (SM-LWL) is provided per mode carried in the multi-mode light waveguide (MM-LWL).

37. Device according to claim 35, wherein an electrical circuit is provided, which performs separation of the signals after coherent detection, preferably using a cross-mode interference canceller (XMIC).

38. Device according to claim 35, wherein a free-beam arrangement having lenses or other imaging elements such as curved mirrors or holograms is provided in the coupling zone (KZ).

39. Device according to claim 28, wherein the mode demultiplexer (MD) performs superimposition of the signal of the local oscillator (LO) with the signal to be detected.

40. Device according to claim 39, wherein a gradient lens (GL_LO) is provided, which converts the output signal of the local oscillator (LO) into a parallel beam and brings it together with the signal to be detected in a semi-transparent mirror (TS), wherein subsequently, coupling the two signals into a single-mode light waveguide (4) takes place using a gradient lens (GL_aus).

41. Device according to claim 40, wherein the device implements phase diversity and/or polarization diversity.

42. Device according to claim 39, wherein the signal of the local oscillator (LO) can be passed in perpendicular to the plane of the beam guidance of the other signals in the mode demultiplexer (MD).

43. Device according to claim 39, wherein the signal of the local oscillator (LO) is divided up using semi-transparent mirrors (TS) and passed to multiple gradient lenses (GL_LO).