Optical communication network

• US 6,626,590 B1
• Filed: 12/06/1999
• Issued: 09/30/2003
• Est. Priority Date: 12/08/1998
• Status: Expired due to Fees

• Current Assignee: Nippon Telegraph and Telephone Corporation
• Original Assignee: Nippon Telegraph and Telephone Corporation
• Inventors: Koga, Masafumi, Nagatsu, Naohide
• Primary Examiner(s): Pascal, Leslie
• Assistant Examiner(s): Phan, Hanh
• Application Number:
  US09/455,463
• Time in Patent Office: 1,394 Days
• Field of Search: 398/59, 398/82, 398/83, 398/9, 398/45, 398/50, 398/91, 398/79, 398/87
• US Class Current: 398/59
• 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 14/0212 using optical switches or wavelength selective switches [WSS]
• CPC Class Codes: H04J 14/0217 Multi-degree architectures, e.g. having a connection degree greater than two
• CPC Class Codes: H04J 14/0219 Modular or upgradable architectures
• CPC Class Codes: H04J 14/0283 WDM ring architectures
• CPC Class Codes: H04J 14/0295 Shared protection at the optical channel (1:1, n:m)
• CPC Class Codes: H04Q 11/0062 Network aspects
• CPC Class Codes: H04Q 11/0071 Provisions for the electrical-optical layer interface
• CPC Class Codes: H04Q 2011/0015 using splitting combining
• CPC Class Codes: H04Q 2011/0018 using tunable transmitters or receivers
• CPC Class Codes: H04Q 2011/0081 Fault tolerance; Redundancy; Recovery; Reconfigurability

Abstract

A wavelength division multiplexing ring network is constructed using a simple architecture and a fewer number of hardwares between the nodes compared with the conventional ring network. Each node is structured so that any number of multiple waves can be processed, and a fault in the network or within a node is resolved by providing a path-based protection so that switching can be performed without disrupting other nodes or even within one node. The network uses two or four lines of optical fibers, and a half of the fibers are used for communicating in a clockwise direction and a other half of the fibers are used for communicating in a counter-clockwise direction to form a logical network by optical paths contained in optical fibers so as to provide an equal number of relay nodes between two adjacent pairs of nodes throughout the network, where each node includes: multiple optical add/drop circuits; an optical path transmit end and an optical path receive end for freely selecting and outputting multiple combinations of wavelengths to be inserted in each node; and transmission lines provided between the optical add/drop circuits and the optical path transmit end, as well as between the optical add/drop circuits and the optical path receive end for transmitting any multiple waves to be processed within the node so as to establish mutual communication by transmitting processed multiple waves to other nodes. This network design enables to reduce the number of connections between the optical path transmit and receive ends, and also to reduce the number of optical signal op termination circuits.

Claims

1. A wavelength division multiplexing ring network, based on a plurality of lines of optical fibers to connect a plurality of nodes into a ring network architecture, using a half of the fibers for operating in a clockwise direction and a remaining half of the fibers for operating in a counter-clockwise direction to form a logical network comprised by signal channels contained in the optical fibers, wherein each node comprises:

a plurality of optical add/drop circuits connected with the adjacent nodes via optical fibers;

a transmit end which comprises;

an optical sender for selecting and outputting optical signals having different wavelengths to be processed within said node; and

a plurality of wavelength multiplexers, respectively connected to said plurality of optical add/drop circuits, for wavelength-multiplexing the optical signals and sending wavelength-multiplexed signals to the optical add/drop circuits; and

a receive end which comprises a plurality of wavelength de-multiplexers for receiving wavelength-multiplexed signals which are sent from the optical add/drop circuits and include the different wavelengths to be processed within said node, and de-multiplexing the wavelength-multiplexed signals,

wherein the optical add/drop circuits are capable of selecting, for an optical signal of each wavelength used in the wavelength division multiplexing ring network, one of a first mode of receiving the optical signal from an adjacent node and outputting the received signal to the receive end, a second mode of receiving the optical signal from the transmit end and outputting the received signal to an adjacent node, and a third mode of receiving the optical signal from an adjacent node and outputting the received signal to another adjacent node, based on the wavelengths of the optical signals selected and output by the transmit end.

2. A wavelength division multiplexing ring network according to claim 1, wherein said optical sender has a shared spectral source for producing light of a plurality of different fixed-wavelengths;

and an optical switching device for selecting the wavelengths to be processed within the node from said different fixed-wavelengths.

3. A wavelength division multiplexing ring network according to claim 2, wherein said shared spectral source is separated into a plurality of shared spectral sources and each shared spectral source emits a plurality of different wavelengths, and said optical switching device includes a plurality of optical switches for connecting the shared spectral sources in parallel and selecting the wavelengths to be processed within the node.

4. A wavelength division multiplexing ring network according to claim 2, wherein the number of said different fixed-wavelengths is the necessary number of wavelengths for connecting the nodes in a full mesh configuration, or greater.

5. A wavelength division multiplexing ring network according to claim 1, wherein said optical sender has a plurality of wavelength tunable optical senders for outputting the optical signals having the different wavelengths to be processed within the node.

6. A wavelength division multiplexing ring network according to claim 1, wherein electrical signals to be superimposed on each of a plurality of freely selected wavelengths are duplicated to produce first electrical signals and second electrical signals, and if a first signal channel modulated with said first electrical signals, having first wavelength and transmitting in one direction is interrupted, said second electrical signals are used to modulate a wavelength identical to said first wavelength to be inserted in an optical add/drop circuit connected to another optical fiber transmitting in opposite direction to said one direction.

7. A wavelength division multiplexing ring network according to claim 6, wherein said network is operating without a fault on an original signal channel, a new signal channel is created by superimposing new electrical signals, different from said electrical signals, on a wavelength identical to said first wavelength, for inserting in an optical add/drop circuit connected to an optical fiber transmitting optical signals in said reverse direction, and when a fault is developed in said network, said new signal channel is interrupted and said original signal channel is restored.

8. A wavelength division multiplexing ring network according to claim 1, wherein each of a plurality of freely selected wavelengths is duplicated to produce first wave signals and second wave signals to be modulated by electrical signals, and if a first signal channel transmitting in one direction and having a first wavelength modulated with said electrical signals is interrupted, said second wave signals are inserted in an optical add/drop circuit connected to another optical fiber transmitting in opposite direction to said one direction.

9. A wavelength division multiplexing ring network according to claim 8, wherein when said network is operating without a fault on an original signal channel, a new signal channel is created by superimposing said second electrical signals on a wavelength identical to said first wavelength, for inserting in an optical add/drop circuit connected to an optical fiber transmitting optical signals in said reverse direction, and when a fault is developed in said network, said new signal channel is interrupted and said original signal channel is restored.

10. A wavelength division multiplexing ring network according to claim 1, wherein said optical add/drop circuit is comprised by an integrated circuit including one device or two devices selected from the group consisting of optical coupler, wavelength multiplexer, wavelength discriminator and wavelength multi/de-multiplexer.

11. A wavelength division multiplexing ring network according to claim 1, wherein any two adjacent nodes are connected by two optical fibers, each of which transmits multiplexed optical signals from one node to other node based on an equal number of normal-use waves and emergency-use waves;

and wherein each of said two optical fibers provides either a clockwise transmission or a counter-clockwise transmission of optical signals, and said normal-use waves and said emergency-use waves are combined in such a way that an optical fiber transmitting optical signals in one direction contain one identical set of wave combinations for all node connections, while a set of normal-use waves in one direction is used as a set of emergency-use waves in opposite direction, and vice versa.

12. A wavelength division multiplexing ring network according to claim 11, wherein transmission lines are allocated to separate said normal-use waves and said emergency-use waves propagating in signal channels connecting said optical add/drop circuits to said transmit end, and in signal channels connecting said optical add/drop circuits to said receive end.

13. A wavelength division multiplexing ring network according to claim 11, wherein, when said network is operating normally, said emergency-use waves are superimposed with information different from information transmitted during normal operation.

14. A wavelength division multiplexing ring network according to claim 11, wherein a plurality of wavelength multiplexing networks are cross connected to form an enlarged optical communication network.

15. A wavelength division multiplexing ring network according to claim 14, wherein a plurality of wavelength multiplexing networks are cross connected according to a four-fiber ring, network architecture.

16. A wavelength division multiplexing ring network according to claim 14, wherein a plurality of wavelength multiplexing networks are cross connected in such a way that one network being connected to other network will not disrupt optical communication in said other network.