Optical add/drop node and method

• US 6,842,562 B2
• Filed: 05/30/2002
• Issued: 01/11/2005
• Est. Priority Date: 05/30/2002
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Network Communications Incorporated (Fujitsu Limited)
• Inventors: Takeguchi, Koji, Kinoshita, Susumu
• Primary Examiner(s): Bovernick, Rodney
• Assistant Examiner(s): PAK, SUNG H
• Application Number:
  US10/159,307
• Publication Number:
  US 20030223682A1
• Time in Patent Office: 957 Days
• Field of Search: 385/24, 385/31, 398/43, 398/66, 398/68, 398/72
• US Class Current: 385/24
• CPC Class Codes: H04J 14/0204 Broadcast and select arrangements, e.g. with an optical splitter at the input before adding or dropping
• CPC Class Codes: H04J 14/0205 Select and combine arrangements, e.g. with an optical combiner at the output after adding or dropping
• CPC Class Codes: H04J 14/0206 Express channels arrangements
• CPC Class Codes: H04J 14/0209 Multi-stage arrangements, e.g. by cascading multiplexers or demultiplexers
• CPC Class Codes: H04J 14/021 Reconfigurable arrangements, e.g. reconfigurable optical add/drop multiplexers [ROADM] or tunable optical add/drop multiplexers [TOADM]
• CPC Class Codes: H04J 14/0212 using optical switches or wavelength selective switches [WSS]
• CPC Class Codes: H04J 14/0213 Groups of channels or wave bands arrangements
• CPC Class Codes: H04J 14/0227 Operation, administration, maintenance or provisioning [OAMP] of WDM networks, e.g. media access, routing or wavelength allocation
• CPC Class Codes: H04J 14/0241 Wavelength allocation for communications one-to-one, e.g. unicasting wavelengths
• CPC Class Codes: H04J 14/0283 WDM ring architectures
• CPC Class Codes: H04J 14/0287 Protection in WDM systems
• CPC Class Codes: H04J 14/0289 Optical multiplex section protection
• CPC Class Codes: H04J 14/0291 Shared protection at the optical multiplex section (1:1, n:m)
• CPC Class Codes: H04J 14/0294 Dedicated protection at the optical channel (1+1)
• CPC Class Codes: H04J 14/0295 Shared protection at the optical channel (1:1, n:m)
• CPC Class Codes: H04J 14/0297 Optical equipment protection

Abstract

An add/drop node (OADN) comprises a network optical fiber carrying a signal on an optical network. A network drop splitter is coupled to the network optical fiber and to stages of drop splitters, the stages of drop splitters being operable to passively split an optical signal from the network drop splitter into multiple copies of the signal. The OADN further comprises at least one filter operable to receive at least a copy of the signal from at least one drop splitter to create a filtered copy, and further comprises at least one broadband receiver operable to receive the filtered copy from the filter.

Claims

1. An add/drop node for an optical network, comprising:

a network drop splitter operable to be coupled to a network optical fiber and to stages of drop splitters, the network drop splitter operable to passively split an optical signal received from the network optical fiber into multiple copies of the signal, the stages of drop splitters operable to passively split at least one of the copies of the optical signal from the network drop splitter into additional copies of the signal;

a plurality of filters, each of the filters operable to filter at least one copy of the signal from at least one drop splitter of the stages of drop splitters so as to pass a specific traffic channel to a coupled receiver; and

a channel reuse module operable to be coupled to the network optical fiber and further operable to selectively terminate portions of the signal on the network optical fiber, wherein the channel reuse module comprises a demultiplexer, a multiplexer, and a plurality of optical switches operable to terminate selected wavelengths from the signal, the optical switches coupled between the demultiplexer and the multiplexer and operable to forward non-terminated channels to the multiplexer.

2. The add/drop node of claim 1, wherein the filter comprises a tunable filter.

3. The add/drop node of claim 1, wherein the receiver comprises a broadband receiver.

4. The add/drop node of claim 1, further comprising a network add splitter coupled to the network optical fiber and to stages of add splitters, the stages of add splitters operable to passively combine optical signals from a plurality of transmitters onto the network optical fiber via the network add splitter.

5. The add/drop node of claim 4, further comprising a plurality of amplifiers operable to amplify the signal from the transmitters.

6. The add/drop node of claim 5, further comprising at least one filter operable to reduce the noise of the amplifier.

7. The add/drop node of claim 1, further comprising a redundant tunable filter operable to pass a specific traffic channel to a broadband receiver in the event of a failure of the specific traffic channel to pass to its normally intended receiver.

21. The add/drop node of claim 1, wherein the network drop splitter is operable to passively split the optical signal into a first copy of the optical signal communicated to the stages of drop splitters and a second copy that is continued along the optical fiber.

8. An optical network, comprising:

a network optical fiber carrying a signal on the optical network; and

at least one add/drop node, the add/drop node comprising;

a network drop splitter operable to be coupled to the network optical fiber and to stages of drop splitters and operable to passively split the signal received from the network optical fiber into multiple copies of the signal, the stages of drop splitters operable to passively split at least one of the copies of the optical signal from the network drop splitter into additional copies of the signal;

a plurality of filters, each of the filters operable to receive at least one copy of the signal from at least one drop splitter of the stages of drop splitters and to filter the copy to pass a specific traffic channel to a coupled broadband receiver; and

a channel reuse module operable to be coupled to the network optical fiber and further operable to selectively terminate portions of the signal on the network optical fiber, wherein the channel reuse module comprises a demultiplexer, a multiplexer, and a plurality of optical switches operable to terminate selected wavelengths from the signal, the optical switches coupled between the demultiplexer and the multiplexer and operable to forward non-terminated channels to the multiplexer.

9. The optical network of claim 8, wherein the add/drop node further comprises a network add splitter coupled to the network optical fiber and to stages of add splitters, the stages of add splitters operable to passively combine optical signals from a plurality of transmitters onto the network optical fiber via the network add splitter.

22. The optical network of claim 8, wherein the network drop splitter is operable to passively split the optical signal into a first copy of the optical signal communicated to the stages of drop splitters and a second copy that is continued along the optical fiber.

10. A method of managing signals on an optical network, comprising:

transmitting a plurality of optical signals from a plurality of transmitters;

passively combining the plurality of optical signals into an add signal;

passively combining the add signal to a passthrough signal to generate an egress signal for transport on an optical network;

passively splitting an ingress optical signal from the network into a transport signal and a drop signal;

passively splitting the drop signal into multiple copies of the drop signal;

filtering each of the multiple drop signals to pass from each of the multiple drop signals a selected drop channel;

receiving the selected drop channels at receivers; and

selectively passing by a channel reuse module at least selected channels of the transport signal as the passthrough signal, wherein the channel reuse module comprises a demultiplexer, a multiplexer, and a plurality of optical switches operable to terminate selected wavelengths from the signal, the optical switches coupled between the demultiplexer and the multiplexer and operable to forward non-terminated channels to the multiplexer.

11. The method of claim 10, further comprising amplifying at least one of the optical signals transmitted from the plurality of transmitters.

12. The method of claim 10, wherein the passing of at least selected channels of the transport signal comprises filtering the signal.

13. The method of claim 10, wherein the passing of at least selected channels of the transport signal comprises terminating the signal with an optical switch.

14. The method of claim 10, wherein the passing of at least a selected channels of the transport signal comprises terminating selected grouping paths.

15. An add/drop node for an optical network, comprising:

a transport element operable to passively drop local drop traffic from an ingress signal to a distributor and to passively add local add traffic from a combiner to a passthrough signal to generate an egress signal; and

a channel reuse module operable to selectively terminate one or more channels of the ingress signal to generate the passthrough signal, wherein the channel reuse module comprises a demultiplexer, a multiplexer, and a plurality of optical switches operable to terminate selected wavelengths from the signal, the optical switches coupled between the demultiplexer and the multiplexer and operable to forward non-terminated channels to the multiplexer.

16. An add/drop node for an optical network, comprising:

means for transmitting a plurality of optical signals;

means for passively combining the plurality of optical signals into an add signal;

means for passively combining the add signal to a passthrough signal to generate an egress signal for transport on an optical network;

means for passively splitting an ingress optical signal from the network into a transport signal and a drop signal;

means for passively splitting the drop signal into multiple copies of the drop signal;

means for filtering each of the multiple drop signals to pass from each of the multiple drop signals a selected drop channel;

means for receiving the selected drop channels; and

means for selectively passing by a channel reuse module at least selected channels of the transport signal as the passthrough signal, wherein the channel reuse module comprises a demultiplexer, a multiplexer, and a plurality of optical switches operable to terminate selected wavelengths from the signal, the optical switches coupled between the demultiplexer and the multiplexer and operable to forward non-terminated channels to the multiplexer.

17. The add/drop node of claim 16, further comprising means for amplifying at least one of the optical signal transmitted from the means for transmitting.

18. The method of claim 16, wherein the means for passing the at least selected channels of the transport signal comprises a filter.

19. The method of claim 16, wherein the means for passing the at least selected channels of the transport signal comprises an optical switch.

20. An add/drop node for an optical network, comprising:

a network drop splitter operable to passively drop from the optical network a combined signal, the combined signal comprising a plurality of traffic channels;

a passive distributor coupled to the network drop splitter, the passive distributor comprising a plurality of stages of drop splitters, each of the stages operable to passively split each of one or more copies of the combined signal provided to the stage into a plurality of copies of the combined optical signal;

the passive distributor further comprising a plurality of filters coupled to the stages of drop splitters, each filter operable to filter a copy of the combined signal so as to pass a specific traffic channel to a coupled receiver; and

a channel reuse module operable to be coupled to the network optical fiber and further operable to selectively terminate portions of the signal on the network optical fiber, wherein the channel reuse module comprises a demultiplexer, a multiplexer, and a plurality of optical switches operable to terminate selected wavelengths from the signal, the optical switches coupled between the demultiplexer and the multiplexer and operable to forward non-terminated channels to the multiplexer.

23. An add/drop node for an optical network, comprising:

a network drop splitter operable to be coupled to a network optical fiber and to stages of drop splitters, the network drop splitter operable to passively split an optical signal received from the network optical fiber into multiple copies of the signal, the stages of drop splitters operable to passively split at least one of the copies of the optical signal from the network drop splitter into additional copies of the signal;

a plurality of filters, each of the filters operable to filter at least one copy of the signal from at least one drop splitter of the stages of drop splitters so as to pass a specific traffic channel to a coupled receiver; and

a channel reuse module operable to be coupled to the network optical fiber and further operable to selectively terminate portions of the signal on the network optical fiber, wherein the channel reuse module comprises;

a circulator;

a demultiplexer coupled to the circulator;

a plurality of tunable filters coupled to the demultiplexer, at least one tunable filter being operable to attenuate a demultiplexed signal; and

a plurality of mirrors coupled to the plurality of tunable filters and operable to reflect the attenuated signals in order to terminate selected wavelengths from the signal on the network optical fiber.

24. An add/drop node for an optical network, comprising:

a transport element operable to passively drop local drop traffic from an ingress signal to a distributor and to passively add local add traffic from a combiner to a passthrough signal to generate an egress signal; and

a channel reuse module operable to selectively terminate one or more channels of the ingress signal to generate the passthrough signal, wherein the channel reuse module comprises;

a circulator;

a demultiplexer coupled to the circulator;

a plurality of tunable filters coupled to the demultiplexer, at least one tunable filter being operable to attenuate a demultiplexed signal; and

a plurality of mirrors coupled to the plurality of tunable filters and operable to reflect the attenuated signals in order to terminate selected wavelengths from the signal on the network optical fiber.

25. An add/drop node for an optical network, comprising:

a network drop splitter operable to passively drop from the optical network a combined signal, the combined signal comprising a plurality of traffic channels;

a passive distributor coupled to the network drop splitter, the passive distributor comprising a plurality of stages of drop splitters, each of the stages operable to passively split each of one or more copies of the combined signal provided to the stage into a plurality of copies of the combined optical signal;

the passive distributor further comprising a plurality of filters coupled to the stages of drop splitters, each filter operable to filter a copy of the combined signal so as to pass a specific traffic channel to a coupled receiver; and

a channel reuse module operable to be coupled to the network optical fiber and further operable to selectively terminate portions of the signal on the network optical fiber, wherein the channel reuse module comprises;

a circulator;

a demultiplexer coupled to the circulator;

a plurality of tunable filters coupled to the demultiplexer, at least one tunable filter being operable to attenuate a demultiplexed signal; and

a plurality of mirrors coupled to the plurality of tunable filters and operable to reflect the attenuated signals in order to terminate selected wavelengths from the signal on the network optical fiber.