Method and apparatus for enabling a single fiber-working on an optical fiber
A method and apparatus for transporting data through a single optical fiber (SOF) the method comprising the steps of providing (S 1 ) transmission Tx, wavelength division multiplexed, WDM, data channels and reception Rx, wavelength division multiplexed, WDM, data channels having the same frequency grid with frequency gaps between the WDM data channels; frequency shifting (S 2 ) the Tx-WDM data channels and/or the Rx-WDM data channels to avoid spectral overlap between the Tx-WDM data channels and the Rx-WDM data channels; combining (S 3 ) the frequency shifted Tx-WDM data channels and the frequency shifted Rx-WDM data channels; and transporting (S 4 ) data via the combined WDM data channels through said single optical fiber (SOF) in opposite directions.
1. A method for transporting data through a single optical fiber the method comprising the steps of:
providing transmission of wavelength division multiplexed Tx-WDM data channels and reception of wavelength division multiplexed Rx-WDM data channels having the same frequency grid with frequency gaps between the WDM data channels;
frequency shifting the Tx-WDM data channels and/or the Rx-WDM data channels to avoid spectral overlap between the Tx-WDM data channels and the Rx-WDM data channels;
combining the frequency shifted Tx-WDM data channels and the frequency shifted Rx-WDM data channels; and
transporting data via the combined WDM data channels through said single optical fiber (SOF) in opposite directions,
wherein the frequency shifted Tx-WDM data channels and the frequency shifted Rx-WDM data channels are combined by interleaving the frequency shifted Tx-WDM data channels and the frequency shifted Rx-WDM data channels, and
wherein the frequency shifted Tx-WDM data channels and the frequency shifted Rx-WDM data channels are combined by coupling the frequency shifted Tx-WDM data channels and the frequency shifted Rx-WDM data channels by means of a passive optical interleaver or a passive optical coupler.
2. The method according to claim 1 wherein the Tx-WDM data channels and the Rx-WDM data channels are frequency shifted with a frequency shift of at least the Nyquist spectral bandwidth of the respective WDM data channels.
3. The method according to claim 1 wherein all Tx-WDM data channels and/or all Rx-WDM data channels are frequency shifted simultaneously to avoid spectral overlap between the Tx-WDM data channels and the Rx-WDM data channels on said single optical fiber.
4. The method according to claim 1 wherein the Tx-WDM data channels and the Rx-WDM data channels are frequency shifted by a frequency shifter.
5. The method according to claim 1 wherein the Tx-WDM data channels are frequency upshifted by a frequency shifter on a transmission side of the single optical fiber to avoid spectral overlap between the Tx-WDM data channels and the Rx-WDM data channels.
6. The method according to claim 1 wherein the Tx-WDM data channels are frequency upshifted positively with a frequency shift by a first frequency shifter on a transmission side of said single optical fiber and frequency downshifted back negatively with the same frequency shift by a second frequency shifter on the reception side of said single optical fiber.
7. The method according to claim 1 wherein both the Tx-WDM data channels and the Rx-WDM data channels are frequency shifted relative to each other by a first frequency shifter on a transmission side of said single optical fiber and by a second frequency shifter on a reception side of said single optical fiber.
8. The method according to claim 1 wherein the frequency shift is realized by an IQ Mach-Zehnder modulator, by four-wave mixing in a highly non-linear fiber and/or by cascaded frequency shifting using a Chi2 non-linearity in periodically poled lithium niobate.
9. The method according to claim 1 wherein the frequency shift is adjusted in response to a control signal received from a network management system.
10. The method according to claim 1 wherein the Tx-WDM data channels are provided by transmit ports of multiple transponders and multiplexed or coupled to provide a first frequency spectrum forming a transponder frequency grid with frequency gaps between the Tx-WDM data channels.
11. The method according to claim 1 wherein the frequency shifted Tx-WDM data channels and the frequency shifted Rx-WDM data channels are combined to provide a second frequency spectrum forming a fiber frequency grid without frequency gaps between the WDM data channels on said single optical fiber.
12. The method according to claim 11 wherein a frequency distance between two adjacent Tx-WDM data channels in said first frequency spectrum is at least twice the frequency distance between a Tx-WDM data channel and an Rx-WDM data channel in said second signal spectrum on said single optical fiber.
13. An SFW-apparatus for enabling a single fiber working, SFW, where data is transportable through a single optical fiber, said SFW-apparatus comprising:
an optical transponder interface adapted to provide transmission of wavelength division multiplexed Tx-WDM data channels and reception of wavelength division multiplexed Rx-WDM data channels having the same frequency grid with frequency gaps between the WDM data channels;
a frequency shifter adapted to perform frequency shifting of the Tx-WDM data channels and/or the Rx-WDM data channels to avoid a spectral overlap between the Tx-WDM data channels and the Rx-WDM data channels;
an optical combiner adapted to combine the frequency shifted Tx-WDM data channels and the frequency shifted Rx-WDM data channels for the single optical fiber,
wherein the frequency shifted Tx-WDM data channels and the frequency shifted Rx-WDM data channels are combined by interleaving the frequency shifted Tx-WDM data channels and the frequency shifted Rx-WDM data channels, and
wherein the frequency shifted Tx-WDM data channels and the frequency shifted Rx-WDM data channels are combined by coupling the frequency shifted Tx-WDM data channels and the frequency shifted Rx-WDM data channels by means of a passive optical interleaver or a passive optical coupler.
14. The SFW-apparatus according to claim 13 wherein the frequency shift is realized by an IQ Mach-Zehnder modulator, by four-wave mixing in a highly non-linear fiber and/or by cascaded frequency shifting using Chi2 non-linearity in periodically poled lithium niobate.
15. An optical network comprising network nodes connected to each other via a single optical fiber wherein each network node of said optical network comprises an SFW-apparatus comprising:
an optical transponder interface adapted to provide transmission of wavelength division multiplexed Tx-WDM data channels and reception of wavelength division multiplexed Rx-WDM data channels having the same frequency grid with frequency gaps between the WDM data channels;
a frequency shifter adapted to perform frequency shifting of the Tx-WDM data channels and/or the Rx-WDM data channels to avoid a spectral overlap between the Tx-WDM data channels and the Rx-WDM data channels;
an optical combiner adapted to combine the frequency shifted Tx-WDM data channels and the frequency shifted Rx-WDM data channels for the single optical fiber,
wherein the frequency shifted Tx-WDM data channels and the frequency shifted Rx-WDM data channels are combined by interleaving the frequency shifted Tx-WDM data channels and the frequency shifted Rx-WDM data channels, and
wherein the frequency shifted Tx-WDM data channels and the frequency shifted Rx-WDM data channels are combined by coupling the frequency shifted Tx-WDM data channels and the frequency shifted Rx-WDM data channels by means of a passive optical interleaver or a passive optical coupler.