BIDIRECTIONAL AND CONFIGURABLE DIRECTIONAL RAMAN PUMPING APPARATUS

Abstract

A Raman pumping device (10) for amplifying a data optical signal in a fiber optic transmission system, comprising first and second ports (12a, 12b) through which the data optical signal may respectively enter and exit the Raman pumping device (10), a Raman pump source (14) for generating a Raman pump signal, and at least one combiner (16) for combining the Raman pump signal with the data optical signal. The Raman pumping device (10) allows for selectively combining the Raman pump signal generated by the same Raman pump source (14), or at least parts of the same Raman pump source (14) codirectionally or counterdirectionally with the data optical signal.

Claims

1. A Raman pumping device for amplifying a data optical signal in a fiber optic transmission system, comprising: first and second ports through which the data optical signal may respectively enter and exit the Raman pumping device; a Raman pump source for generating a Raman pump signal; and at least one combiner for combining the Raman pump signal with the data optical signal; wherein the Raman pumping device allows for selectively combining the Raman pump signal generated by the same Raman pump source, or at least parts of the same Raman pump source codirectionally or counterdirectionally with the data optical signal.

2. The Raman pumping device of claim 1, wherein the Raman pumping device allows for selectively combining the Raman pump signal generated by the same Raman pump source, or at least parts of the same Raman pump source codirectionally or counterdirectionally with the data optical signal without disconnecting the Raman pumping device from the fiber optic transmission system.

3. The Raman pumping device of claim 1, wherein the Raman pumping device further allows for selectively combining a first part of the Raman pump signal codirectionally with the data optical signal and a second part of the Raman pump signal counterdirectionally with the data optical signal.

4. The Raman pumping device of claim 3, wherein the power ratio of the first and second parts of the Raman pump signal is selectively adjustable.

5. The Raman pumping device of claim 1, wherein the Raman pumping device comprises an optical tunable splitter or an optical switch for selectively directing the Raman pump signal to one or both of: a first combiner arranged to combine the Raman pump signal and the data optical signal codirectionally; and a second combiner arranged to combine the Raman pump signal and the data optical signal counterdirectionally.

6. The Raman pumping device of claim 5, wherein the first and second combiners are integrated in a four-port combiner having first and second ports respectively arranged to combine the Raman pump signal and the data optical signal codirectionally and counterdirectionally.

7. The Raman pumping device of claim 5, wherein the Raman pump source and the optical tunable splitter or the optical switch are comprised in an integrated device.

8. The Raman pumping device of claim 5, further comprising a controlling unit, wherein the controlling unit is configured for controlling the operation of the optical tunable splitter or the optical switch and of the Raman pump source.

9. The Raman pumping device of claim 8, further comprising a spectral filtering structure, wherein the spectral filtering structure is configured for directing at least part of the data optical signal to an analyzing unit, wherein the analyzing unit is part of or in communication with the controlling unit.

10. The Raman pumping device of claim 1, wherein the Raman pumping device is symmetrical to an extent that it allows for an installation in a fiber optic transmission system in a first and a second installation orientation, wherein in the first and second installation orientations, the roles of the first and second ports are interchanged.

11. The Raman pumping device of claim 1, wherein the Raman pump source comprises: a fiber amplifier having a first end coupled with the first port and a second end coupled with the second port; an amplifier pump source for pumping a fiber amplifying signal into the fiber amplifier; and first and second seed light sources for providing seed light to be amplified by the fiber amplifier to thereby generate the Raman pump signal; wherein the first and second seed light sources are coupled to inject their corresponding seed light into the fiber amplifier in opposite directions.

12. The Raman pumping device of claim 11, wherein the data signal is transmitted between the first and second ports through the fiber amplifier, wherein the fiber amplifier forms the at least one combiner for combining the Raman pump signal with the data optical signal.

13. The Raman pumping device of claim 12, wherein the amplifier pump provides light with a power at least 3 times higher than the light provided by the first or second seed light sources.

14. The Raman pumping device of claim 11, wherein the first and second seed light sources provide light with different wavelengths.

15. The Raman pumping device of claim 11, wherein the fiber amplifier comprises a thulium-doped fiber.

16. The Raman pumping device of claim 1, further comprising a signal tap and a first extraction port, wherein the signal tap is configured for extracting at least part of the data optical signal and directing it to the first extraction port, wherein the first extraction port is configured for being connected to a further component.

17. Raman pumping device of claim 16, further comprising a second extraction port, wherein the signal tap is configured for extracting at least part of the data optical signal and for directing the extracted part of the data optical signal to the first extraction port when the data optical signal propagates from the first port to the second port and for directing the extracted part of the data optical signal to the second extraction port when the data optical signal propagates from the second port to the first port, wherein the second extraction port is configured for being connected to a further component, in particular with a photodetector or with a light source.

18. The Raman pumping device of claim 16, wherein the signal tap comprises an optical filter configured for extracting at least part of the data optical signal lying within a predefined wavelength range.

19. The Raman pumping device of claim 17, further comprising an extraction switch, wherein the extraction switch allows for selectively connecting one of the first extraction port and the second extraction port with the further component, in particular with the photodetector or with the light source.

20. The Raman pumping device of claim 17, further comprising an extraction combiner, wherein the extraction combiner is configured for connecting the first extraction port and the second extraction port with a further component.

21. The Raman pumping device of claim 16, further comprising a connection interface allowing for interchangeably connecting one of a photodetector and a light source with the Raman pumping device, such that the one of a photodetector and a light source be connected with at least one of the first extraction port and second extraction port.

22. The Raman pumping device of claim 1, further comprising an optical measuring device and a first connection node, wherein the first connection node is arranged upstream with respect to the propagation direction of the data optical signal from the at least one combiner and connected to the measuring device; and/or a second connection node, wherein the second connection node is arranged downstream with respect to the propagation direction of the data optical signal from the at least one combiner and connected to the measuring device.

23. The Raman pumping device of claim 22, further comprising a measuring switching device, wherein the measuring switching device is configured to selectively connect the measuring device to one of the first and second connection nodes.

24. The Raman pumping device of claim 23, wherein the measuring device and the measuring switching device are comprised in an integrated device.

25. The Raman pumping device of claim 22, wherein one or both of the first connection node and the second connection node comprises an optical filter.

26. The Raman pumping device of claim 25, wherein the measuring device is an optical time-domain reflectometer.

27. The Raman pumping device of claim 22, wherein the measuring device is an optical frequency-domain reflectometer.

28. A method for selectively amplifying a data optical signal in a fiber optic transmission system codirectionally or counterdirectionally with the Raman pump device of claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0049] FIG. 1 shows a Raman pumping device according to embodiments of the invention.

[0050] FIG. 2 shows a Raman pumping device according to an embodiment of the invention comprising an optical tunable splitter.

[0051] FIG. 3 shows a Raman pumping device according to an embodiment of the invention comprising an optical switch.

[0052] FIG. 4 shows a Raman pumping device according to an embodiment of the invention comprising a fiber amplifier.

[0053] FIG. 5 shows a Raman pumping device according to an embodiment of the invention comprising an optical switch, a controlling unit, a spectral filtering, a measuring device and a measuring switching device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0054] For the purposes of promoting an understanding of the principles of the invention, reference will now be made to a preferred embodiment illustrated in the drawings, and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated apparatus and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur now or in the future to one skilled in the art to which the invention relates.

[0055] FIG. 1a shows a representation of a Raman pumping device 10 for amplifying a data optical signal in a fiber optic transmission system according to a preferred embodiment of the invention. The Raman pumping device 10 comprises first and second ports 12a, 12b through which the data optical signal may respectively enter and exit the Raman pumping device 10. The device 10 also comprises a Raman pump source 14 for generating a Raman pump signal and at least one combiner 16 for combining the Raman pump signal generated by the Raman pump source 14, or at least parts of the same, codirectionally or counterdirectionally with the data optical signal.

[0056] The Raman pump signal generated by the Raman pump source 14 is combined with the data optical signal by the combiner 16 such that the data optical signal is amplified in the fiber optic transmission system by means of Raman scattering. The Raman pumping device 10 can be installed in a fiber optic transmission system according to a first installation orientation such that the data optical signal is transmitted from the first port 12a to the second port 12b and the Raman pump signal is combined with the data optical signal by the combiner 16 counterdirectionally. According to a second installation orientation, resulting for example from a physical inversion of the Raman pumping device 10 with respect to the first installation orientation, the data optical signal is transmitted from the second port 12b to the second port 12a and the Raman pump signal is combined with the data optical signal by the combiner 16 codirectionally.

[0057] In the embodiment shown in FIG. 1b, the Raman pumping device 10 further comprises a signal tap 20 and a first extraction port 22. The signal tap 20 is an optical filter configured for extracting at least part of the data optical signal lying within a predefined wavelength range and directing it to the first extraction port 22.

[0058] Additionally, as shown in FIG. 1c, other preferred embodiments of the invention comprise a second extraction port 23. The signal tap 20 is configured for extracting at least part of the data optical signal and for directing the extracted part of the data optical signal to the first extraction port 22 when the data optical signal propagates from the first port 12a to the second port 12b. When the data optical signal propagates from the second port 12b to the first port 12a, the signal tap 20 directs the extracted part of the data optical signal to the second extraction port 23. The first and second extraction ports 22, 23 are configured as part of a connection interface for being interchangeably connected to further components, in particular with a photodetectors and/or a light source. An example of this is shown in FIG. 1d, where photodetectors 24 are connected to the first and second extraction ports 22, 23

[0059] The Raman pumping device 10 of FIG. 1 can also comprise an extraction switch or an extraction combiner (not shown in the figure, see FIG. 5) allowing the connection of the first and second extraction ports 22, 23 with a single further component of equipment 24, such that the extracted part of the data optical signal reaches said component of equipment 24 irrespectively of the propagation direction of the data optical signal. Furthermore, an optical isolator with switchable transmission direction as described in DE 196 532 76 A1 may be arranged between the ports 12a and 12b.

[0060] FIG. 2 shows another preferred embodiment of the Raman pumping device 10 comprising an optical tunable splitter 30, a first combiner 16a arranged to combine the Raman pump signal and the data optical signal counterdirectionally and a second combiner 16b arranged to combine the Raman pump signal and the data optical signal codirectionally. The Raman pumping device 10 of FIG. 2 allows for selectively combining a first part of the Raman pump signal generated by the Raman pump source 14 counterdirectionally with the data optical signal at the first combiner 16a. A second part of the Raman pump signal generated by the Raman pump source 14 is combined codirectionally with the data optical signal and the second combiner 16b. By operating the optical tunable splitter 30, the power ratio of the first and second parts of the Raman pump signal can be selectively adjusted. The optical tunable splitter 30 is wavelength independent, such that the first and second parts of the Raman pump signal comprise equal wavelengths. The device 10 also comprises a signal tap 20 for extracting at least part of the data optical signal and directing it to a further component 24, which in the example shown is a photodetector.

[0061] FIG. 3a shows a related embodiment of the Raman pumping device 10 of FIG. 2 in which the first and second combiners 16a, 16b are integrated in a single four-port combiner 16 which allows to combine the Raman pump signal and the data optical signal counterdirectionally and/or codirectionally. The device 10 comprises an optical switch 32, which allows for selectively combining the Raman pump signal generated by the Raman pump source 14 with the data optical signal codirectionally or counterdirectionally at the combiner 16. The optical switch 32 can also be switched to an OFF position, such that the Raman pump signal from the Raman pump source 14 is not transmitted to the combiner 16 and the device 10 is hence deactivated. Furthermore, as shown in FIG. 3b, a signal tap 20 for extracting at least part of the data optical signal and directing it to a further component 24, in the example shown a photodetector, may be incorporated in the device 10.

[0062] FIG. 4a shows a Raman pumping device 10 comprising a fiber amplifier 40, an amplifier pump source 42 for pumping a fiber amplifying signal into the fiber amplifier 40 and first and second seed light sources 44a, 44b for providing seed light to be amplified in the fiber amplifier 40 to thereby generate the Raman pump signal. The seed light generated by the seed light sources 44a, 44b is directed to the fiber amplifier 40 by corresponding combiners 48a, 48b. The fiber amplifying signal generated by the amplifier pump source 42 is directed to the fiber amplifier 40 by a combiner 46. The data optical signal, the seed light and the fiber amplifying signal are combined in the fiber amplifier 40.

[0063] The seed light sources 44a, 44b are low-power pumps providing light with a power of 200 mW only. The first seed light source 44a provides light with a wavelength of 1453 nm whereas the second seed light source 44b provides light with a wavelength of 1438 nm. The combiners 48a, 48b are wavelength-selective and are configured such that no seed light from one seed light source 44a, 44b is directed to of the other seed light source 44b, 44a, respectively. For example, the combiner 48a is configured such that seed light generated by the seed light source 44b and amplified by the fiber amplifier 40 is not directed to the seed light source 44a, but is just allowed to pass towards a first end 41b of the fiber amplifier 40. Similarly, the combiner 48b is configured such that the seed light generated by the seed light source 44a and amplified by the fiber amplifier 40 is not directed to the seed light source 44b, but is just allowed to pass towards a second end 41b of the fiber amplifier 40. The amplifier pump 42 is a high-power pump providing light with a power of 3 W and a wavelength of 1020 nm. Alternatively, the light provided by the seed light sources can comprise a combination of wavelengths around 800 nm (e.g. 798 nm) and around 1400 nm.

[0064] The fiber amplifier 40 comprises a thulium-doped fiber that enables amplification of the seed light generated by the seed light sources 44a, 44b in the fiber amplifier 40. The data optical signal, however, is not amplified in the fiber amplifier 40, due to its higher wavelength. Once it has been amplified in the fiber amplifier 40 by the fiber amplifying signal generated by the amplifier pump 42, the seed light generated by the seed light sources 44a and/or 44b constitutes the Raman pump signal which amplifies the data optical signal in the fiber optic transmission system by means of Raman scattering. Note that the fiber amplifying signal is likewise a pump signal for pumping the thulium-doped fiber, but is not referred to as a pump signal herein, such as not to be confused with the Raman pump signal.

[0065] The seed light generated by the first seed light source 44a is injected into the fiber amplifier 40 in the direction from the first end 41a to the second end 41b of the fiber amplifier 40. The seed light generated by the second seed light source 44b is injected into the fiber amplifier 40 in the direction from the second end 41b to the first end 41a of the fiber amplifier 40, that is, in the opposite direction. While not shown in FIG. 4, the first end 41a of the fiber amplifier 40 is coupled to the first port 12a and the second end 41b is coupled to the second port 12b of the Raman pumping device 10. This coupling can be such that the data optical signal is transmitted through the fiber amplifier 40 itself or such that the data optical signal is transmitted through an additional fiber that would be arranged in parallel to the fiber of the fiber amplifier 40. An example of such an arrangement with an additional fiber 47 comprising an optional isolator 49 is shown in FIG. 4b. In any case, by selectively operating the seed light sources 44a, 44b, the data optical signal may be amplified codirectionally, counterdirectionally or in both directions. Furthermore, the power of the seed light sources 44a, 44b can be adjusted such that a desired power ratio between codirectional and counterdirectional amplification is given.

[0066] FIG. 5 shows a Raman pumping device 10 of FIG. 3a in which the Raman pump source 14 and the optical switch 32 are comprised in an integrated device 33. The device 10 further comprises a wavelength independent splitter 18, a controlling unit 50 and a spectral filtering structure 52. The wavelength independent splitter 18 is configured for extracting at least part of the data optical signal and/or at least part of the Raman pump signal and directing it to the spectral filtering structure 52. The spectral filtering structure 52 is configured for receiving the part of the data optical signal and/or the part of the Raman pump signal extracted by the wavelength independent splitter 18 and for directing said extracted part of the data optical signal and/or of the Raman pump signal to an internal analyzing unit, which is in communication with the controlling unit 50, and which in the embodiment shown is comprised in the controlling unit 50. The controlling unit 50 is configured for controlling the operation of the optical switch 32 and of the Raman pump source 14.

[0067] The device 10 further comprises an optical measuring device 56, first and second connection nods 54a, 54b and a measuring switching device 58. The measuring device 56 and the measuring switching device 58 are comprised in an integrated device 60. The first connection nod 54a is arranged after the first port 12a, upstream with respect to the propagation direction of the data optical signal from the combiner 16 and selectively connectable to the measuring device 56 via the measuring switch 58. The second connection nod 54b is arranged before the second port 12b, downstream with respect to the propagation direction of the data optical signal from the combiner 16 and selectively connectable to the measuring device 56 via the measuring switch 58. The measuring switching device 58 is configured to selectively connect the measuring device 56 to one of the first and second connection nod 54a and 54b, such that the measuring device 56 can selectively and independently measure properties of the parts of the fiber optic transmission system connected to the connection nods 54a and 54b.

[0068] The controlling unit 50 can then determine whether Raman pumping should take place or not, and if so, in which direction and with which power it should take place by adjusting the optical switch 32 and the Raman pump source 14. This is done based on the information provided by the measuring device 56 and the spectral filtering structure 52. Such information may comprise tilt/ripple information, laser safety supervision information, traffic channels measurement, information about the physical characteristics of the fiber, and information about the channel powers and their spectral distribution.

[0069] In FIGS. 2, 3, and 5, either an optical switch 32 or a tunable splitter 30 is shown. However, in all embodiments of the invention shown in these figures, the tunable splitter 30 can be substituted by an optical switch 32 and vice versa. Using an optical switch, the data optical signal can be selectively amplified either codirectionally or counterdirectionally, whereas a tunable splitter further allows to selectively amplify the data optical signal both codirectionally and counterdirectionally.

[0070] Although a preferred exemplary embodiment is shown and specified in detail in the drawings and the preceding specification, these should be viewed as purely exemplary and not as limiting the invention. It is noted in this regard that only the preferred exemplary embodiment is shown and specified, and all variations and modifications should be protected that presently or in the future lie within the scope of protection of the invention as defined in the claims.

LIST OF REFERENCE SIGNS

[0071] 10 Raman pumping device

[0072] 12a first port

[0073] 12b second port

[0074] 14 Raman pump source

[0075] 16, 16a, 16b combiners

[0076] 18 wavelength independent splitter

[0077] 20 signal tap

[0078] 22, 23 extraction ports

[0079] 24, 26 component of equipment (e.g. photodetectors)

[0080] 30 optical tunable splitter

[0081] 32 optical switch

[0082] 40 fiber amplifier

[0083] 42 amplifier pump source

[0084] 44a, 44b seed light sources

[0085] 46, 48a, 48b combiners

[0086] 50 controlling unit

[0087] 52 spectral filter

[0088] 54a, 54b connection nods

[0089] 56 measuring device

[0090] 58 switching device

[0091] 60 integrated device