Optical communication system Number:7,522,837 from the United States Patent and Trademark Office (PTO) owispatent An optical communication system is constructed which enables highly reliable and flexible connection to communication nodes connected to a path establishment circuit, by utilizing wavelength-routing characteristics of a path establishment circuit such as an arrayed waveguide grating. The optical communication system has multiple communication nodes having a signal output port and signal input port pair, and a path establishment circuit having multiple optical input ports and multiple optical output ports which are set so that optical signals input from the respective optical input ports are output to predetermined optical output ports corresponding to the wavelengths of the optical signals.<H communication, Optical, Optical, communi, 7522837.html, Patent, pto, 7522837

Title: Optical communication system

Abstract: An optical communication system is constructed which enables highly reliable and flexible connection to communication nodes connected to a path establishment circuit, by utilizing wavelength-routing characteristics of a path establishment circuit such as an arrayed waveguide grating. The optical communication system has multiple communication nodes having a signal output port and signal input port pair, and a path establishment circuit having multiple optical input ports and multiple optical output ports which are set so that optical signals input from the respective optical input ports are output to predetermined optical output ports corresponding to the wavelengths of the optical signals.

Patent Number: 7,522,837 Issued on 04/21/2009 to Tanobe, et al.

Inventors: Tanobe; Hiromasa (Tokyo, JP), Okada; Akira (Tokyo, JP), Matsuoka; Morito (Atsugi, JP), Noguchi; Kazuto (Atsugi, JP), Sakamoto; Takashi (Zama, JP), Moriwaki; Osamu (Zama, JP)
Assignee: Nippon Telegraph and Telephone Corporation (Tokyo, JP)

Appl. No.: 10/717,225

Filed: November 19, 2003

Foreign Application Priority Data


Nov 21, 2002 [JP]			2002-338242
Sep 18, 2003 [JP]			2003-326317

Current U.S. Class: 398/63 ; 398/3; 398/48; 398/59

Current International Class: H04J 14/00 (20060101)

Field of Search: 398/3,7,45,48-50,55-59,63,66

References Cited [Referenced By]

U.S. Patent Documents


5663818	September 1997	Yamamoto et al.
6643463	November 2003	Suzuki et al.
6718140	April 2004	Kamei et al.
7181140	February 2007	Ovadia
2002/0154357	October 2002	Ozveren et al.

Foreign Patent Documents


56-111340	Sep., 1981	JP
58-120330	Jul., 1983	JP
58-123246	Jul., 1983	JP
58-161488	Sep., 1983	JP
06-216910	Aug., 1994	JP
8-242208	Sep., 1996	JP
11-041270	Feb., 1999	JP
2000-201112	Jul., 2000	JP
2000-232420	Aug., 2000	JP
2001-53760	Feb., 2001	JP
2001-346235	Dec., 2001	JP

Other References

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"32.times.32 full-mesh (1024 path) wavelength-routing WDM network based on uniform-loss cyclic-frequency arrayed-waveguide grating", K. Kato, et al., Electronics Letters, vol. 36, No. 15, pp. 1294-1296, Jul. 20, 2000. cited by other .
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"Logical Topology Dynamically-Reconfigurable Network with Wavelength Routing Full-mesh (AWG-STAR) Technology" by Hiromasa Tanobe, et al., http://www.ieice.org/; IEICE Technical Report, NS2002-260-332, Mar. 7, 2003, ISSN 0913-5685, vol. 102, No. 392; 7 pages. cited by other .
Takahashi et al., "Impact of Crosstalk in an Arrayed-Waveguide Multiplexer on NXN Optical Interconnection", Journal of Lightwave Technology, vol. 14, No. 6, Jun. 1996. cited by other .
Chang-Joon Chae, "A Flexible and Protected Virtual Optical Ring Network", IEEE Photonics Technology Letters, vol. 14, No. 11, Nov. 2002. cited by other .
Chang-Joon Chae, et al., "A Protected Optical Star-Shaped Ring Network Using an NxN Arrayed Waveguide Grating and Incoherent Light Sources", IEEE Photonics Technology Letters, vol. 13, No. 8, Aug. 2001, 3 pages. cited by other .
Charles A. Brackett, "Dense Wavelength Division Multiplexing Networks: Principles and Applications", IEEE Journal on Selected Areas in Communications, vol. 8, No. 6, Aug. 1990, 17 pages. cited by other .
Mansour I. Irshid, et al., "A WDM Cross-Connected Star Topology for Multihop Lightwave Networks", Journal of Lightwave Technology, vol. 10, No. 6, Jun. 1992, 8 pages. cited by other.

Primary Examiner: Singh; Dalzid
Attorney, Agent or Firm: Harness, Dickey & Pierce, P.L.C.

Claims

What is claimed is:

1. An optical communication system comprising: an N.times.N wavelength path establishment circuit having N input ports and N output ports, N being an integer of at least 2, outputting light input from an input port to a different output port depending on the wavelength of the input light, and the wavelength of light output from an output port being different depending on the input port; n communication nodes, n being an integer at least 2 and not greater than N, for outputting information of an input optical signal, as is or after changing a part of the information, as an optical signal of a predetermined wavelength; and optical waveguides for connecting the input ports and the output ports of the N.times.N wavelength path establishment circuit, and the communication nodes, wherein for at least some of the n communication nodes, in order to form a first logical-ring transmission path where an optical signal transmitted from one communication node circulates in a clockwise direction and returns to the one communication node via other communication nodes or to form both the first logical-ring transmission path and a second logical-ring transmission path where an optical signal transmitted from the one communication node circulates in a counterclockwise direction and returns to the one communication node via the other communication nodes, a correlation of wavelengths for connecting between the input ports and the output ports of the N.times.N wavelength path establishment circuit, wavelengths of optical signals output from the respective communication nodes, and connections between the input ports and the output ports of the N.times.N wavelength path establishment circuit, and the respective communication nodes are set.

2. An optical communication system comprising: an N.times.N wavelength path establishment circuit having N input ports and N output ports, N being an integer of at least 2, outputting light input from an input port to a different output port depending on the wavelength of the input light and the wave length of light output from an output port being different depending on the input port; n communication nodes, n being an integer at least 2 and not greater than N, for outputting information of an input optical data signal, as is or after changing a part of the information, as an optical data signal of a predetermined wavelength; and optical waveguides for connecting the input ports and the output ports of the N.times.N wavelength path establishment circuit, and the communication nodes, wherein for at least some of the n communication nodes, in order to form at least two logical-ring transmission paths where an optical data signal transmitted from one communication node returns to the one communication node via other communication nodes, a correlation of wavelengths for connecting between the input ports and the output ports of the N.times.N wavelength path establishment circuit, wavelengths of at least two optical data signals output from the respective communication nodes, and connections between the input ports and the output ports of the N.times.N wavelength path establishment circuit, and the respective communication nodes are set.

3. An optical communication system according to claim 2, wherein each communication nodes is provided with: a device which transfers the optical data signal so that an optical data signal loaded with information of communication nodes circulates the respective communication nodes forming the logical-ring transmission path; a memory for storing information of the optical data signal which has been received; and a transfer device which writes the information of the optical data signal to the memory, and appends information to the optical data signal which is transmitted.

4. An optical communication system according to claim 3, further comprising a management device which monitors and controls the condition of the respective communication nodes, wherein a management signal for managing a communication node is: transferred between the management device and the communication node by an optical signal, of which wavelength is different from the wavelength of the optical data signal or the wavelengths of the optical data signal and the optical control signal; transferred via an optical waveguide which is different from an optical waveguide for transmitting the optical data signal or both the optical data signal and the optical control signal; or transferred via an electric signal.

5. An optical communication system according to claim 2, further comprising a management device which monitors and controls the condition of the respective communication nodes, wherein a management signal for managing a communication node is: transferred between the management device and the communication node by an optical signal, of which wavelength is different from the wavelength of the optical data signal or the wavelengths of the optical data signal and the optical control signal; transferred via an optical waveguide which is different from an optical waveguide for transmitting the optical data signal or both the optical data signal and the optical control signal; or transferred via an electric signal.

6. An optical communication system comprising: an N.times.N wavelength path establishment circuit having N input ports and N output ports, N being an integer of at least 2, outputting light input from an input port to a different output port depending on the wavelength of the input light, and the wavelength of light output from an output port being different depending on the input port; n communication nodes, n being an integer at least 2 and not greater than N, for outputting information of an input optical data signal, as is or after changing a part of the information, as an optical data signal of a predetermined wavelength; and optical waveguides for connecting the input ports and the output ports of the N.times.N wavelength path establishment circuit, and the communication nodes, wherein for at least some of the n communication nodes, in order to form at least one logical-ring transmission path where an optical data signal transmitted from one communication node returns to the one communication node via other communication nodes, a correlation of wavelengths for connecting between the input ports and the output ports of the N.times.N wavelength path establishment circuit, wavelengths of optical data signals out put from the respective communication nodes, and connections between the input ports and the output ports of the N.times.N wavelength path establishment circuit, and the respective communication nodes are set, and each communication node sets the wavelength of an optical control signal for link query between the communication nodes which is output so as to form the logical-ring transmission path where the optical control signal circulates in reverse to the optical data signal.

7. An optical communication system according to claim 6, wherein each communication node splits a part of an input optical data signal and transmits the split optical data signal as the optical control signal for link query.

8. An optical communication system according to claim 7, wherein a communication node which cannot receive the optical control signal for link query sets the output wavelength of the optical data signal to a wavelength corresponding to a communication node which skips at least the next communication node on the transmission path of the optical data signal.

9. An optical communication system according to claim 8, wherein each communication nodes is provided with: a device which transfers the optical data signal so that an optical data signal loaded with information of communication nodes circulates the respective communication nodes forming the logical-ring transmission path; a memory for storing information of the optical data signal which has been received; and a transfer device which writes the information of the optical data signal to the memory, and appends information to the optical data signal which is transmitted.

10. An optical communication system according to claim 9, further comprising a management device which monitors and controls the condition of the respective communication nodes, wherein a management signal for managing a communication node is: transferred between the management device and the communication node by an optical signal, of which wavelength is different from the wavelength of the optical data signal or the wavelengths of the optical data signal and the optical control signal; transferred via an optical waveguide which is different from an optical waveguide for transmitting the optical data signal or both the optical data signal and the optical control signal; or transferred via an electric signal.

11. An optical communication system according to claim 8, further comprising a management device which monitors and controls the condition of the respective communication nodes, wherein a management signal for managing a communication node is: transferred between the management device and the communication node by an optical signal, of which wavelength is different from the wavelength of the optical data signal or the wavelengths of the optical data signal and the optical control signal; transferred via an optical waveguide which is different from an optical waveguide for transmitting the optical data signal or both the optical data signal and the optical control signal; or transferred via an electric signal.

12. An optical communication system according to claim 7, wherein each communication nodes is provided with: a device which transfers the optical data signal so that an optical data signal loaded with information of communication nodes circulates the respective communication nodes forming the logical-ring transmission path; a memory for storing information of the optical data signal which has been received; and a transfer device which writes the information of the optical data signal to the memory, and appends information to the optical data signal which is transmitted.

13. An optical communication system according to claim 12, further comprising a management device which monitors and controls the condition of the respective communication nodes, wherein a management signal for managing a communication node is: transferred between the management device and the communication node by an optical signal, of which wavelength is different from the wavelength of the optical data signal or the wavelengths of the optical data signal and the optical control signal; transferred via an optical waveguide which is different from an optical waveguide for transmitting the optical data signal or both the optical data signal and the optical control signal; or transferred via an electric signal.

14. An optical communication system according to claim 7, further comprising a management device which monitors and controls the condition of the respective communication nodes, wherein a management signal for managing a communication node is: transferred between the management device and the communication node by an optical signal, of which wavelength is different from the wavelength of the optical data signal or the wavelengths of the optical data signal and the optical control signal; transferred via an optical waveguide which is different from an optical waveguide for transmitting the optical data signal or both the optical data signal and the optical control signal; or transferred via an electric signal.

15. An optical communication system according to claim 6, wherein each communication node configures a leading part of the optical data signal with an unmodulated signal, modulates the unmodulated part of the optical data signal input to each communication node, and transmits the modulated optical data signal as the optical control signal for link query.

16. An optical communication system according to claim 15, wherein a communication node which cannot receive the optical control signal for link query sets the output wavelength of the optical data signal to a wavelength corresponding to a communication node which skips at least the next communication node on the transmission path of the optical data signal.

17. An optical communication system according to claim 16, wherein each communication nodes is provided with: a device which transfers the optical data signal so that an optical data signal loaded with information of communication nodes circulates the respective communication nodes forming the logical-ring transmission path; a memory for storing information of the optical data signal which has been received; and a transfer device which writes the information of the optical data signal to the memory, and appends information to the optical data signal which is transmitted.

18. An optical communication system according to claim 17, further comprising a management device which monitors and controls the condition of the respective communication nodes, wherein a management signal for managing a communication node is: transferred between the management device and the communication node by an optical signal, of which wavelength is different from the wavelength of the optical data signal or the wavelengths of the optical data signal and the optical control signal; transferred via an optical waveguide which is different from an optical waveguide for transmitting the optical data signal or both the optical data signal and the optical control signal; or transferred via an electric signal.

19. An optical communication system according to claim 16, further comprising a management device which monitors and controls the condition of the respective communication nodes, wherein a management signal for managing a communication node is: transferred between the management device and the communication node by an optical signal, of which wavelength is different from the wavelength of the optical data signal or the wavelengths of the optical data signal and the optical control signal; transferred via an optical waveguide which is different from an optical waveguide for transmitting the optical data signal or both the optical data signal and the optical control signal; or transferred via an electric signal.

20. An optical communication system according to claim 15, wherein each communication nodes is provided with: a device which transfers the optical data signal so that an optical data signal loaded with information of communication nodes circulates the respective communication nodes forming the logical-ring transmission path; a memory for storing information of the optical data signal which has been received; and a transfer device which writes the information of the optical data signal to the memory, and appends information to the optical data signal which is transmitted.

21. An optical communication system according to claim 20, further comprising a management device which monitors and controls the condition of the respective communication nodes, wherein a management signal for managing a communication node is: transferred between the management device and the communication node by an optical signal, of which wavelength is different from the wavelength of the optical data signal or the wavelengths of the optical data signal and the optical control signal; transferred via an optical waveguide which is different from an optical waveguide for transmitting the optical data signal or both the optical data signal and the optical control signal; or transferred via an electric signal.

22. An optical communication system according to claim 15, further comprising a management device which monitors and controls the condition of the respective communication nodes, wherein a management signal for managing a communication node is: transferred between the management device and the communication node by an optical signal, of which wavelength is different from the wavelength of the optical data signal or the wavelengths of the optical data signal and the optical control signal; transferred via an optical waveguide which is different from an optical waveguide for transmitting the optical data signal or both the optical data signal and the optical control signal; or transferred via an electric signal.

23. An optical communication system according to claim 6, wherein a communication node which cannot receive the optical control signal for link query sets the output wavelength of the optical data signal to a wavelength corresponding to a communication node which skips at least the next communication node on the transmission path of the optical data signal.

24. An optical communication system according to claim 23, wherein each communication nodes is provided with: a device which transfers the optical data signal so that an optical data signal loaded with information of communication nodes circulates the respective communication nodes forming the logical-ring transmission path; a memory for storing information of the optical data signal which has been received; and a transfer device which writes the information of the optical data signal to the memory, and appends information to the optical data signal which is transmitted.

25. An optical communication system according to claim 24, further comprising a management device which monitors and controls the condition of the respective communication nodes, wherein a management signal for managing a communication node is: transferred between the management device and the communication node by an optical signal, of which wavelength is different from the wavelength of the optical data signal or the wavelengths of the optical data signal and the optical control signal; transferred via an optical waveguide which is different from an optical waveguide for transmitting the optical data signal or both the optical data signal and the optical control signal; or transferred via an electric signal.

26. An optical communication system according to claim 23, further comprising a management device which monitors and controls the condition of the respective communication nodes, wherein a management signal for managing a communication node is: transferred between the management device and the communication node by an optical signal, of which wavelength is different from the wavelength of the optical data signal or the wavelengths of the optical data signal and the optical control signal; transferred via an optical waveguide which is different from an optical waveguide for transmitting the optical data signal or both the optical data signal and the optical control signal; or transferred via an electric signal.

27. An optical communication system according to claim 6, wherein each communication nodes is provided with: a device which transfers the optical data signal so that an optical data signal loaded with information of communication nodes circulates the respective communication nodes forming the logical-ring transmission path; a memory for storing information of the optical data signal which has been received; and a transfer device which writes the information of the optical data signal to the memory, and appends information to the optical data signal which is transmitted.

28. An optical communication system according to claim 27, further comprising a management device which monitors and controls the condition of the respective communication nodes, wherein a management signal for managing a communication node is: transferred between the management device and the communication node by an optical signal, of which wavelength is different from the wavelength of the optical data signal or the wavelengths of the optical data signal and the optical control signal; transferred via an optical waveguide which is different from an optical waveguide for transmitting the optical data signal or both the optical data signal and the optical control signal; or transferred via an electric signal.

29. An optical communication system according to claim 6, further comprising a management device which monitors and controls the condition of the respective communication nodes, wherein a management signal for managing a communication node is: transferred between the management device and the communication node by an optical signal, of which wavelength is different from the wavelength of the optical data signal or the wavelengths of the optical data signal and the optical control signal; transferred via an optical waveguide which is different from an optical waveguide for transmitting the optical data signal or both the optical data signal and the optical control signal; or transferred via an electric signal.

30. An optical communication system comprising: an N.times.N wavelength path establishment circuit having N input ports and N output ports, N being an integer of at least 2, outputting light input from an input port to a different output port depending on the wavelength of the input light, and the wavelength of light output from an output port being different depending on the input port; n communication nodes, n being an integer at least 2 and not greater than N, for outputting information of an input optical data signal, as is or after changing a part of the information, as an optical data signal of a predetermined wavelength; and optical waveguides for connecting the input ports and the output ports of the N.times.N wavelength path establishment circuit, and the communication nodes, wherein for at least some of the n communication nodes, in order to form at least one logical-ring transmission path where an optical data signal transmitted from one communication node returns to the one communication node via other communication nodes, a correlation of wavelengths for connecting between the input ports and the output ports of the N.times.N wavelength path establishment circuit, wavelengths of o optical data signals out put from the respective communication nodes, and connections between the input ports and the output ports of the N.times.N wavelength path establishment circuit, and the respective communication nodes are set, and each communication nodes is provided with: a device which transfers the optical data signal so that an optical data signal loaded with information of communication nodes circulates the respective communication nodes forming the logical-ring transmission path; a memory for storing information of the optical data signal which has been received; and a transfer device which writes the information of the optical data signal to the memory, and appends information to the optical data signal which is transmitted.

31. An optical communication system according to claim 30, further comprising a management device which monitors and controls the condition of the respective communication nodes, wherein a management signal for managing a communication node is: transferred between the management device and the communication node by an optical signal, of which wavelength is different from the wavelength of the optical data signal or the wavelengths of the optical data signal and the optical control signal; transferred via an optical waveguide which is different from an optical waveguide for transmitting the optical data signal or both the optical data signal and the optical control signal; or transferred via an electric signal.

32. An optical communication system comprising: an N.times.N wavelength path establishment circuit having N input ports and N output ports, N being an integer of at least 2, outputting light input from an input port to a different output port depending on the wavelength of the input light, and the wavelength of light output from an output port being different depending on the input port; n communication nodes, n being an integer at least 2 and not greater than N, for outputting information of an input optical data signal, as is or after changing a part of the information, as an optical data signal of a predetermined wavelength; and optical waveguides for connecting the input ports and the output ports of the N.times.N wavelength path establishment circuit, and the communication nodes, a management device which monitors and controls the condition of the respective communication nodes, wherein for at least some of the n communication nodes, in order to form at least one logical-ring transmission path where an optical data signal transmitted from one communication node returns to the one communication node via other communication nodes, a correlation of wavelengths for connecting between the input ports and the output ports of the N.times.N wavelength path establishment circuit, wavelengths of optical data signals output from the respective communication nodes, and connections between the input ports and the output ports of the N.times.N wavelength path establishment circuit, and the respective communication nodes are set, and a management signal for managing a communication node is: transferred between the management device and the communication node by an optical signal, of which wavelength is different from the wavelength of the optical data signal or the wavelengths of the optical data signal and the optical control signal; transferred via an optical waveguide which is different from an optical waveguide for transmitting the optical data signal or both the optical data signal and the optical control signal; or transferred via an electric signal.

33. An optical communication system for communicating between multiple communication nodes for outputting information of an input optical data signal, as is or after changing a part of the information, as an optical data signal of a predetermined wavelength, comprising: an N.times.N wavelength path establishment circuit, which has N input ports and N output ports, N being any integer which satisfies 2.ltoreq.n.ltoreq.N where n is the number of the communication nodes, connected to the communication nodes via an optical waveguide, and light input from an input port is output to a different output port depending on the wavelength of the input light, and the wavelength of light output from an output port is different depending on the input port; a database prestored with output wavelengths used in the case in which a signal is routed from a predetermined input port to a predetermined output port in the N.times.N wavelength path establishment circuit; and a controlling device which receives control information including a connection request from a communication node, refers to the database and reads out an output wavelength which should be set by the communication node, and transmits control information for instructing the output wavelength to the communication node which transmitted the connection request, wherein for at least some of the n communication nodes, in order to form a logical-ring transmission path where an optical data signal transmitted from one communication node returns to the one communication node via other communication nodes, a correlation of wavelengths for connecting between the input ports and the output ports of the N.times.N wavelength path establishment circuit, wavelengths of optical data signals output from respective communication nodes, and connections between the input ports and the output ports of the N.times.N wavelength path establishment circuit, and the respective communication nodes are set.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an optical communication system for connecting communication nodes. Specifically, the present invention relates to an optical communication system (optical network system) for flexibly connecting multiple communication nodes at low cost and with high reliability by utilizing the wavelength-routing characteristics of an arrayed waveguide grating, and for sharing memories loaded in respective communication nodes at low cost. More specifically, the present invention relates to an optical communication system which enables flexible connection of communication nodes with high reliability, by utilizing the wavelength-routing characteristics used in an arrayed waveguide grating or the like.

Priority is claimed on Japanese Patent Application No. 2002-338242 filed on Nov. 21, 2002 and Japanese Patent Application No. 2003-326317 filed on Sep. 18, 2003, the contents of which are incorporated herein by reference.

2. Description of the Related Art

With the developments in computerized offices and computerized administration, a demand for sharing information between respective communication nodes (nodes), for delivering information to a specific communication node, or for distributed processing of the specific information between respective communication nodes is increasing in intranets and networks in organizations. Therefore, a method for realizing this with low cost, easily, and stably has been desired.

As a method for realizing this, as shown in FIG. 53, it is considered to annularly connect by optical fibers, shared memory which is loaded in respective communication nodes on the network, and to sequentially transmit frames loaded with communication data between these communication nodes. FIG. 53 shows a system comprising four communication nodes 5201 to 5204. Communication modules 5012 loaded with optical transceivers and shared memories, are installed in the communication nodes 5201 to 5204, and the flow of frames F1 to F4 loaded with the respective data of the communication nodes 5201 to 5204, forms a logical ring topology. The frames F1 to F4 loaded with the respective data of the communication nodes 5201 to 5204, circulate the logical ring topology so that the data is shared between the communication nodes (for example, refer to "optical channel-enabled PMC card", <URL: http://avaldata.com/avaldata/product/module_product/giga/apm425/apm425.ht- ml>)

Here, as a method for configuring a network by connecting communication nodes, as shown in FIG. 54A to FIG. 54B, there is so called a ring-shaped network system which physically and annularly connects respective communication nodes, represented by a token ring (for example, refer to "IEEE 802.5 Documents, 802.5c-1991(R1997) Supplement to IEEE Std 802.5-1989", especially, chapter 2, <URL: http://www.8025.org/documents/>). In FIG. 54A, reference symbols 13001 to 1300n denote nodes.

Regarding the token ring scheme shown in FIG. 54A and FIG. 54B, by only arranging a transmission/reception circuit (transceiver) in respective communication nodes, and simply chain connecting sequentially all the communication nodes by an optical waveguide such as an optical fiber, it is possible to connect many communication nodes by transmission processing, with low cost. Therefore, it is suitable as a network which can be configured easily.

According to this scheme, as shown in FIG. 53, it is possible to share data of the memories, which all the connected communication nodes have, so that delivering, circulating, and distributed processing of signals between all the communication nodes becomes feasible.

However, in the abovementioned scheme, the problem is such that, in the case where any fault such as disconnection of an optical fiber or failure of a communication node occurs, all the other connected communication nodes are affected. That is to say, in the case where a fault occurs, the communication node that detected the fault outputs a fault signal, the respective communication nodes temporarily withdraw from the network to which they belong, and attempt automatic diagnosis in order to reconfigure the network around the faulty area. When they attempt automatic diagnosis, all the other communication nodes connected to the network are affected, and communication disconnection occurs. Furthermore, another problem is such that, in the case where a communication node is to be added to the same ring, the overall network must be paused.

Hence, in a ring-shaped network, a method for avoiding the influence of a communication fault by using a reverse route is used. For example, there is an FDDI (Fiber Distributed Data Interface) as a token ring optical communication system which duplicates a ring network by an optical fiber. In the FDDI, when a fault occurs, the reverse route can be realized by using a redundant optical fiber. However, not only is there a problem in that the fault avoiding system becomes extremely large scale, but also a redundant configuration of the transmission optical fiber is indispensable. Moreover, a token ring does not function as a shared memory network unless the ring is completed. Therefore, a convenient and stable optical communication system alternative has been desired.

Furthermore, even if the redundant configuration is employed, if a communication faults occur at more than one communication node, it becomes impossible to form a logical ring topology. Therefore, there is the drawback in that communication nodes where no fault has occurred are isolated.

Moreover, it is also considered to share the memory which the respective communication nodes accommodated in a ring network have. However, due to the abovementioned problems, there is a need for a highly reliable optical communication system as an alternative to this.

SUMMARY OF THE INVENTION

The present invention takes into consideration the abovementioned problems, with an object of realizing an optical communication system which can connect multiple communication nodes at low cost and with high reliability, and which can share memory loaded in respective communication nodes at low cost.

Also, an object of the present invention is to construct an optical communication system which enables highly reliable and flexible connection to communication nodes connected to a path establishment circuit such as an arrayed waveguide grating, by utilizing wavelength-routing characteristics of a path establishment circuit such as an arrayed waveguide grating.

In order to solve the abovementioned problem, an optical communication system according to a first aspect of the present invention comprising: an N.times.N wavelength path establishment circuit having N input ports and N output ports, N being an integer of at least 2, outputting light input from an input port to a different output port depending on the wavelength of the input light, and the wavelength of light output from an output port being different depending on the input port; n communication nodes, n being an integer at least 2 and not greater than N, for outputting information of an input optical data signal, as is or after changing a part of the information, as an optical data signal of a predetermined wavelength; and optical waveguides for connecting the input ports and the output ports of the N.times.N wavelength path establishment circuit, and the communication nodes, wherein for at least some of the n communication nodes, in order to form at least one logical-ring transmission path where an optical data signal transmitted from one communication node returns to the one communication node via other communication nodes, a correlation of wavelengths for connecting between the input ports and the output ports of the N.times.N wavelength path establishment circuit, wavelengths of optical data signals output from the respective communication nodes, and connections between the input ports and the output ports of the N.times.N wavelength path establishment circuit, and the respective communication nodes are set.

Moreover, in an optical communication system according to a second aspect of the present invention, in the abovementioned optical communication system, for at least some of the n communication nodes, in order to form at least two logical-ring transmission paths where an optical data signal transmitted from one communication node returns to the one communication node via other communication nodes, a correlation of wavelengths for connecting between the input ports and the output ports of the N.times.N wavelength path establishment circuit, wavelengths of at least two optical data signals output from the respective communication nodes, and connections between the input ports and the output ports of the N.times.N wavelength path establishment circuit, and the respective communication nodes are set.

Furthermore, in an optical communication system according to a third aspect of the present invention, in the abovementioned optical communication system of the first aspect, each communication node sets the wavelength of an optical control signal for link query between the communication nodes which is output so as to form the logical-ring transmission path where the optical control signal circulates in reverse to the optical data signal. In an optical communication system according to a fourth aspect of the present invention, in the optical communication system according to the third aspect, each communication node splits a part of an input optical data signal and transmits the split optical data signal as the optical control signal for link query. In an optical communication system according to a fifth aspect of the present invention, in the optical communication system according to the third aspect, each communication node configures a leading part of the optical data signal with an unmodulated signal, modulates the unmodulated part of the optical data signal input to each communication node, and transmits the modulated optical data signal as the optical control signal for link query.

Furthermore, in an optical communication system according to a sixth aspect of the present invention, in the optical communication system according to any one of the third to the fifth aspects, a communication node which cannot receive the optical control signal for link query sets the output wavelength of the optical data signal to a wavelength corresponding to a communication node which skips at least the next communication node on the transmission path of the optical data signal.

Furthermore, in an optical communication system according to a seventh aspect of the present invention, in an optical communication system according to any one of the abovementioned aspects, each communication nodes is provided with: a device which transfers the optical data signal so that an optical data signal loaded with information of communication nodes circulates the respective communication nodes forming the logical-ring transmission path; a memory for storing information of the optical data signal which has been received; and a transfer device which writes the information of the optical data signal to the memory, and appends information to the optical data signal which is transmitted.

Moreover, in an optical communication system according to an eighth aspect of the present invention, in an optical communication system according to any one of the abovementioned aspects, further comprising a management device which monitors and controls the condition of the respective communication nodes, wherein a management signal for managing a communication node is: transferred between the management device and the communication node by an optical signal, of which wavelength is different from the wavelength of the optical data signal or the wavelengths of the optical data signal and the optical control signal; transferred via an optical waveguide which is different from an optical waveguide for transmitting the optical data signal or both the optical data signal and the optical control signal; or transferred via an electric signal.

Furthermore, an optical communication system according to a ninth aspect of the present invention is an optical communication system for communicating between multiple communication nodes for outputting information of an input optical data signal, as is or after changing a part of the information, as an optical data signal of a predetermined wavelength, comprising: an N.times.N wavelength path establishment circuit, which has N input ports and N output ports, N being any integer which satisfies 2.ltoreq.n.ltoreq.N where n is the number of the communication nodes, connected to the communication nodes via an optical waveguide, and light input from an input port is output to a different output port depending on the wavelength of the input light, and the wavelength of light output from an output port is different depending on the input port; a database prestored with output wavelengths used in the case in which a signal is routed from a predetermined input port to a predetermined output port in the N.times.N wavelength path establishment circuit; and a controlling device which receives control information including a connection request from a communication node, refers to the database and reads out an output wavelength which should be set by the communication node, and transmits control information for instructing the output wavelength to the communication node which transmitted the connection request, wherein for at least some of the n communication nodes, in order to form a logical-ring transmission path where an optical data signal transmitted from one communication node returns to the one communication node via other communication nodes, a correlation of wavelengths for connecting between the input ports and the output ports of the N.times.N wavelength path establishment circuit, wavelengths of optical data signals output from respective communication nodes, and connections between the input ports and the output ports of the N.times.N wavelength path establishment circuit, and the respective communication nodes are set.

According to the above-described optical communication systems, multiple communication nodes (nodes) can be connected at low cost and with high reliability, and sharing of the memories of the respective communication nodes becomes possible.

Moreover, an optical communication system according to a tenth aspect of the present invention comprising: multiple communication nodes each having a pair of a signal output port and a signal input port; and multiple path establishment circuits each having multiple optical input ports and multiple optical output ports which are set so that an optical signal input from an optical input port is output to a predetermined optical output port corresponding to the wavelength of the input optical signal, wherein the signal output port and the signal input port of the pair of each communication node are connected to an optical input port and an optical output port of one of the multiple path establishment circuits, an optical input port of one path establishment circuit is connected to an optical output port of another path establishment circuit, and an optical output port of the one path establishment circuit is connected to an optical input port of the other path establishment circuit.

Moreover, in an optical communication system according to an eleventh aspect of the present invention, in the optical communication system of the tenth aspect, the wavelengths of the optical signals from the signal output ports of the respective communication nodes are arranged so that the connection of the multiple communication nodes forms a logical ring topology.

Moreover, in an optical communication system according to a twelfth aspect of the present invention, in the optical communication system according to the tenth or eleventh aspects, an optical output port of the one path establishment circuit and an optical input port of the other path establishment circuit is connected via a communication node.

An optical communication system according to a thirteenth aspect of the present invention comprising multiple units, each of which comprises: multiple communication nodes each having a pair of a signal output port and a signal input port; multiple optical switches, each of which sets the direction of an optical signal in which the optical signal from one optical input port is output to any of multiple optical output ports; multiple optical multiplexers, each of which multiplexes optical signals from multiple optical input ports, and each of which outputs a multiplexed signal to one optical output port; and a path establishment circuit having multiple optical input ports and multiple optical output ports which is set so that an optical signal input from an input port is output to a predetermined optical output port depending on the wavelength of the input optical signal, wherein, in each of the multiple units, a signal output port of a communication node is connected to an optical input port of the corresponding optical switch, an optical output port of the optical switch is connected to an optical input port of the corresponding optical multiplexer, an optical output port of the optical multiplexer is connected to an optical input port of the corresponding path establishment circuit, and an output port of the path establishment circuit is connected to a signal input port of the corresponding communication node.

An optical communication system according to a fourteenth aspect of the present invention comprising multiple units, each of which comprises: multiple communication nodes each having a pair of a signal output port and a signal input port; multiple optical splitters, each of which splits an optical signal from one optical input port, and each of which outputs split optical signals to multiple optical output ports; multiple optical switches, each of which sets the direction of an optical signal in which the optical signal from any of multiple input ports is output to one optical output port; and a path establishment circuit having multiple optical input ports and multiple optical output ports which is set so that an optical signal input from an optical input port is output to a predetermined optical output port depending on the wavelength of the input optical signal, wherein, in each of the multiple units, a signal output port of a communication node is connected to an optical input port of the corresponding optical splitter, an optical output port of the optical splitter is connected to an optical input port of the corresponding optical switch, an optical output port of the optical switch is connected to an optical input port of the corresponding path establishment circuit, and an output port of the path establishment circuit is connected to a signal input port of the corresponding communication node.

In an optical communication system according to a fifteenth aspect of the present invention, in the optical communication system according to the thirteenth or the fourteenth aspects, the wavelengths of the optical signals from the signal output ports of the respective communication nodes are arranged and the directions of the optical switches are set so that the connection of the multiple communication nodes forms a logical ring topology.

In an optical communication system according to a sixteenth aspect of the present invention, in the optical communication system according to any one of the thirteenth through fifteenth aspects, each of the path establishment circuits comprises an arrayed waveguide grating.

In an optical communication system according to a seventeenth aspect of the present invention, in the optical communication system according to any one of the thirteenth through sixteenth aspects, an optical light source of the communication node comprises a wavelength-tunable optical light source.

In an optical communication system according to an eighteenth aspect of the present invention, in an optical communication system according to any one of the twelfth through seventeenth aspects, a part of the communication nodes is replaced by a repeater having a function for converting wavelength.

In an optical communication system according to a nineteenth aspect of the present invention, in an optical communication system according to the eleventh or fifteenth aspects, each communication node is provided with: a device which transfers an optical data signal loaded with information of communication nodes so that the optical data signal circulates the respective communication nodes on the logical ring topology; a memory for storing information of the optical data signal which has been received; and a transfer device which writes the information of the received optical data signal to the memory, and appends information to an optical data signal which is transmitted.

In an optical communication system according to a twentieth aspect of the present invention, in an optical communication system according to any of the tenth through nineteenth aspects, further comprising a management node which monitors and controls the condition of the respective communication nodes, wherein the respective communication nodes and the management node communicate using an optical signal, of which the wavelength is different from the wavelength of an optical data signal loaded with information of communication nodes.

An optical communication system according to a twenty first aspect of the present invention is an optical communication system for communicating between multiple communication nodes each having a pair of a signal output port and a signal input port, comprising: a path establishment circuit having multiple optical input ports and multiple optical output ports which is previously set so that an optical signal input from an optical input port is output to a predetermined optical output port depending on the wavelength of the input optical signal; a database prestored with output wavelengths used in the case in which a signal is routed from a predetermined optical input port to the predetermined optical output port in the path establishment circuit; and a controlling device which receives control information including a connection request from a communication node, refers to the database and reads out an output wavelength which should be set by the communication node, and transmits control information for instructing the output wavelength to the communication node which transmitted the connection request, wherein the signal output port and the signal input port of the pair of each multiple communication node are connected to an optical input port and an optical output port of the path establishment circuit, and an optical input port of one path establishment circuit is connected to an optical output port of another path establishment circuit, and an optical output port of the one path establishment circuit is connected to an optical input port of the other path establishment circuit.

An optical communication system according to a twenty second aspect of the present invention is an optical communication system for communicating between multiple communication nodes each having a pair of a signal output port and a signal input port, comprising: multiple units, each of which comprises multiple optical switches, each of which sets the direction of an optical signal in which the optical signal from one optical input port is output to any of multiple optical output ports, multiple optical multiplexers, each of which multiplexes optical signals from multiple optical input ports, and each of which outputs a multiplexed optical signal to one optical output port, and a path establishment circuit having multiple optical input ports and multiple optical output ports which is set so that an optical signal input from an optical input port is output to a predetermined optical output port depending on the wavelength of the input optical signal; a database prestored with information of devices connected to the optical input ports and the optical output ports of the optical switches, and output wavelengths used in the case in which an optical signal is routed from a predetermined optical input port to a predetermined optical output port in the path establishment circuits; and a controlling device which receives control information including a connection request from a communication node, refers to the database and reads out an output wavelength which should be set by the communication node, and transmits control information for instructing the output wavelength to the communication node which transmitted the connection request, and also which controls the setting of the directions of the optical switches, wherein, in each of the multiple units, a signal output port of a communication node is connected to an optical input port of the corresponding optical switch, an optical output port of the optical switch is connected to an optical input port of the corresponding optical multiplexer, an optical output port of the optical multiplexer is connected to an optical input port of the corresponding path establishment circuit, and an output port of the path establishment circuit is connected to a signal input port of the corresponding communication node.

An optical communication system according to a twenty third aspect of the present invention is an optical communication system for communicating between multiple communication nodes each having a pair of a signal output port and a signal input port, comprising: multiple units, each of which comprises multiple optical splitters, each of which splits an optical signal from one optical input port, and each of which outputs split optical signals to multiple optical output ports, multiple optical switches, each of which sets the direction of an optical signal in which the optical signal from any of the multiple input ports is output to one optical output port, and a path establishment circuit having multiple optical input ports and multiple optical output ports which is set so that an optical signal input from an input port is output to a predetermined optical output port depending on the wavelength of the input optical signal; a database prestored with information of devices connected to the optical input ports and the optical output ports of the optical switches, and output wavelengths used in the case in which an optical signal is routed from a predetermined optical input port to a predetermined optical output port in the path establishment circuits; and a controlling device which receives control information including a connection request from a communication node, refers to the database and reads out an output wavelength which should be set by the communication node, and transmits control information for instructing the output wavelength to the communication node which transmitted the connection request, and also which controls the setting of the directions of the optical switches, wherein, in each of the multiple units, a signal output port of a communication node is connected to an optical input port of the corresponding optical splitter, an optical output port of the optical splitter is connected to an optical input port of the corresponding optical switch, an optical output port of the optical switch is connected to an optical input port of the corresponding path establishment circuits, and an output port of the path establishment circuit is connected to a signal input port of the corresponding communication node.

Furthermore, the respective configur