Ultra-highspeed packet transfer ring network

• US 20010017866A1
• Filed: 02/28/2001
• Published: 08/30/2001
• Est. Priority Date: 02/28/2000
• Status: Abandoned Application

• Current Assignee: Nippon Telegraph and Telephone Corporation
• Original Assignee: Nippon Telegraph and Telephone Corporation
• Inventors: Yamabayashi, Yoshiaki, Park, Jin Hun, Takada, Atsushi, Imajuku, Wataru
• Application Number:
  US09/793,955
• Publication Number:
  US 20010017866A1
• Time in Patent Office: Days
• US Class Current: 370/535
• CPC Class Codes: H04Q 11/0003 Details
• CPC Class Codes: H04Q 11/0005 Switch and router aspects
• CPC Class Codes: H04Q 11/0066 Provisions for optical burst or packet networks
• CPC Class Codes: H04Q 2011/0041 Optical control
• CPC Class Codes: H04Q 2011/0073 Provisions for forwarding or routing, e.g. lookup tables
• CPC Class Codes: H04Q 2011/0092 Ring

Abstract

In the present ultra-highspeed packet transfer ring network, an add/drop multiplex type node apparatus adds an optical packet to the optical fiber transmission path by preparing a label signal containing information on an address of a destination node apparatus or a routing to the destination node apparatus, and outputs time-sequenced signals to the optical fiber transmission path by multiplexing the optical packet and the label signal by means of wavelength or polarization multiplexing. The add/drop multiplex type node apparatus also receives a label signal by separating and extracting the label signal from the optical fiber transmission path, and determines whether to drop an optical packet corresponding to the label signal to its own node apparatus or to pass the optical packet through with reference to an address or routing information contained in the label signal, and operates an optical switch accordingly. Also, in this ultra-highspeed packet transfer ring network, each node constantly monitors label signals so as to detect any fault developing in the transmission path and to divert the optical packets around the fault. Also, the ultra-highspeed packet transfer ring network enables optical packet compression using a simple circuit by modulating the optical pulses separated by an optical divider with respective data, and multiplexing the modulated pulses again. Also, highspeed optical packet decompression is achieved using a simple circuitry by converting the input optical packets in an OTDM/WDM conversion circuit to different wavelengths and inputting these waves in a wavelength-dependent delay circuit.

Claims

1. An ultra-highspeed optical packet transfer ring network comprised by connecting optical add/drop multiplex type node apparatuses in a ring network for optical packets to be added to, dropped from or passed through said ring network by means of an optical fiber transmission path, wherein a packet transfer control section is provided in each optical add/drop multiplex type node apparatus to manage a flow of incoming packets arriving through the optical fiber transmission path so that an optical packet not addressed to itself is allowed to pass through as an optical packet, and an optical packet addressed to its own node apparatus is dropped for further processing.

2. An ultra-highspeed optical packet transfer ring network according to

claim 1

, wherein said optical add/drop multiplex type node apparatus, when adding an optical packet to the optical fiber transmission path, prepares a label signal containing information on an address of a destination node apparatus or a routing path to the destination node apparatus, and forwards the optical packet together with the label signal by means of wavelength multiplexing or polarization multiplexing;

and

said packet transfer control section acquires an address of a destination node apparatus and routing information of a corresponding optical packet by accessing all the label signals arriving from the optical fiber transmission path by means of wavelength separating or polarization separating.

3. An ultra-highspeed optical packet transfer ring network according to

claim 2

, wherein said optical add/drop multiplex type node apparatus outputs a label signal to the optical fiber transmission path so as to precede a corresponding optical packet by a specific time interval.

4. An ultra-highspeed optical packet transfer ring network according to

claim 2

, wherein at least one of the optical add/drop multiplex type node apparatuses outputs, at given intervals, a label signal to authorize one designated optical node apparatus having a specified address, to add optical packets to the optical fiber transmission path, and any optical node apparatus other than said one designated optical node apparatus receiving said label signal is forbidden to add optical packets to the corresponding slot.

5. An ultra-highspeed optical packet transfer ring network according to

claim 1

, wherein at least one of the optical add/drop multiplex type node apparatuses has a packet compression circuit to compress packets at a compression ratio N, a packet decompression circuit to decompress packets at a packet decompression ratio N and M pieces of optical-to-electrical conversion sections;

and

each of the optical add/drop multiplex type node apparatuses controls adding of optical packet to the optical fiber transmission path so as not to output more than two optical packets addressed to a common address in any contiguous N/M number of slots.

6. An ultra-highspeed optical packet transfer ring network according to

claim 2

, wherein each of the optical add/drop multiplex type node apparatuses receives and sends label signals in a bit-synchronous mode.

7. An ultra-highspeed optical packet transfer ring network according to

claim 6

, wherein unmeaning bits are inserted between label signals.

26. A method for protecting an ultra-highspeed packet transfer ring network according to

claim 1

, wherein said ultra-highspeed packet transfer ring network is a label switched network for transferring packets between nodes according to address information included in label information of each packet;

and

monitors line quality of transmission paths by attaching a path code for detecting or correcting errors in transmission system to each frame of the label information for the node to monitor the label information.

42. An ultra-highspeed optical packet transfer ring network according to

claim 1

, wherein said add/drop multiplex type node apparatus is provided with an optical compression circuit according to

claim 33

, and adds optical packets compressed by a respective optical packet compression circuit to the optical fiber transmission path.

43. An ultra-highspeed optical packet transfer ring network according to

claim 1

, wherein said add/drop multiplex type node apparatus is provided with an optical decompression circuit according to

claim 37

, and decompresses optical packets dropped from the optical fiber transmission path using a respective optical packet decompression circuit.

44. An ultra-highspeed optical packet transfer ring network according to

claim 1

, wherein said add/drop multiplex type node apparatus is provided with an optical decompression circuit according to

claim 39

, and adds optical packets decompressed using a respective optical packet decompression circuit to the optical fiber transmission path.

8. An optical add/drop multiplex type node apparatus for optical packets to be dropped from, added to or cut-through an optical fiber transmission path disposed in a ring network, comprising:

a send packet terminating section for temporarily accumulating packets input from a user side, converting packets to optical packets and outputting, and preparing a label signal containing a n address of a destination node apparatus to correspond to a send-packet or routing information to the destination node apparatus;

an optical circuit section for separating an optical signal input from the optical fiber transmission path to obtain a separated optical packet and an optical label signal, as well as for switching between a bar-state and a cross-state, so that, in the bar-state, two groups of optical packets consisting of said separated optical packet input from the optical fiber transmission path and an optical packet output from the send packet terminating section are received, and said separated optical packet is cut-through without any change to the optical fiber transmission path, while in the cross-state, said separated optical packet input from the optical fiber path side is dropped and output, and said send-optical packet from the send packet terminating section is added to the optical fiber transmission path, and further, an optical add-label signal received is wavelength multiplexed or polarization multiplexed with either an optical pass-packet or an optical add-packet, and sent through to the optical fiber transmission path;

a packet send/receive control section for determining, according to an optical label signal retrieved by the optical circuit section, whether there is a corresponding optical packet, and controlling packet transmission in such a way that;

(a) if an optical packet is addressed to its own node apparatus or a pass-packet is not present and packets are accumulated in the send packet terminating section, a drive signal is output to maintain the optical circuit section in the cross-state, and when packets are accumulated in the send packet terminating section, an optical packet send command signal is output to the send packet terminating section and, at the same time, an optical label signal for a corresponding optical packet to be added to or cut-through the optical fiber transmission path is output at given intervals to the optical circuit section; and

(b) if an optical packet input from the optical fiber side is not addressed to its own node apparatus, a drive signal is output to the optical control section to maintain the bar-state, and an optical label signal relating to an optical pass-packet is output to the optical control section; and

a receive packet terminating section for optical-electrical converting an optical packet separated from the optical fiber path side and addressed to its own node apparatus, and, by accessing a destination user address or routing information to a destination node apparatus included in the packet information obtained by conversion, restoring the optical packet to a state before editing and outputting the restored packet to a specific output port.

9. An optical add/drop multiplex type node apparatus according to

claim 8

, wherein said send packet terminating section is comprised by:

not less than one terminating sections for terminating packets input from a user side according to a relevant interface;

a packet editing sending circuit section for receiving output signals from the terminating section and editing a plurality of packets addressed to node apparatuses having a common destination address into one packet and accumulating edited packets, and, in response to trigger signals from the packet send/receive control section, outputting an edited packets and preparing label signals relating to respective packets and containing addresses of senders and destination node apparatuses or routing information between the sender node apparatuses and the destination node apparatuses, and outputting label signals to the packet send/receive control section;

a first electrical/optical conversion section for converting a packet output from the packet receiving editing circuit section to an optical packet having a packet wavelength λ

P; and

a packet multiplexing section for multiplexing optical packets output from the first electrical/optical conversion section; and

said optical circuit section is comprised by;

an optical label separation section having an input port for connecting to an input optical fiber of the optical fiber transmission path into the optical node apparatus;

an optical label multiplexing section having an output port for connecting to an output optical fiber of the optical fiber transmission path from the optical node apparatus;

a 2×

2 optical switch operated by drive signals output from the packet send/receive control section, and having two input ports, one for receiving an input signal having a packet wavelength λ

P output from the optical label separation section and another for receiving an output signal from the packet multiplexing section, and two output ports, one for outputting an optical packet having a packet wavelength λ

P to the optical label multiplexing section and another for outputting an optical packet addressed to its own node apparatus to the receive packet terminating section; and

said packet send/receive control section is comprised by;

an optical label optical-electrical conversion section for receiving optical label signals having a label wavelength λ

L output from the optical circuit section and performing optical-electrical conversion;

a packet control circuit section for receiving label signals output from the label optical-electrical conversion section on the optical fiber path side and label signals from the send packet terminating section, and controlling packet transmission in such a way that;

(a) if an optical packet is addressed to its own node apparatus or a pass-packet is not present and packets are accumulated in the send packet terminating section, a drive signal is output to maintain the ×

2 optical switch of the optical circuit section in the cross-state, and when there are accumulated packets in the send packet terminating section, an optical packet send command signal is output to the send packet terminating section and, at the same time, an optical label signal relating to an optical packet to be added to or cut- through the optical fiber transmission path is output at given intervals to the optical circuit section; and

(b) if an optical packet input from the optical fiber transmission side is not addressed to its own node apparatus, a drive signal is output to the 2×

2 optical switch of the optical control section to maintain the bar-state and an optical label signal relating to an optical pass-packet is output to the optical control section; and

a second electrical-optical conversion section for converting a label output signal from the packet control circuit section to an optical label signal having a label wavelength λ

L and outputting as a label wavelength input signal to the optical label multiplexing section; and

said receive packet terminating section is comprised by;

a packet optical-electrical conversion section for receiving and performing optical-electrical conversion on an optical packet, separated from the optical circuit section and having a packet wavelength λ

P; and

a packet receiving editing circuit section for re-editing an edited packet to revert to a packet before editing according to a packet output from the packet optical-electrical conversion section by accessing a destination user address contained in the packet information, and sending to a specific output port.

10. An optical add/drop multiplex type node apparatus according to

claim 8

, wherein provided are:

an optical packet compression circuit disposed between the send packet terminating section and the optical circuit for shortening an optical packet duration by narrowing a time interval between optical pulses; and

an optical decompression circuit section disposed between the optical circuit and the receive packet terminating section for reverting an optical packet duration to a pre-compression level.

27. An add/drop multiplex type node apparatus according to

claim 8

, wherein a line quality of a transmission path is monitored by attaching a transmission code for detecting or correcting errors in transmission system to each frame of the label information for the node to monitor the label information.

11. A method for operating an optical add/drop multiplex type node apparatus disposed in an optical fiber transmission path arranged in a ring for an optical packet to be added to, dropped from or cut-through the optical fiber transmission path, comprising:

a step of separating and accessing an optical label signal from an optical signal input from the optical fiber transmission path to generate a separated optical label;

a step of label discriminating for determining, according to the optical label signal separated in the separating step, whether there is a corresponding optical packet and its destination address;

an optical packet sending step for converting a packet input from the user side to an optical packet and outputting the optical packet, when an optical packet in the optical fiber path side is addressed to its own node apparatus or when there is no optical pass-packet, according to a result of the label discriminating step;

an optical switch driving step for outputting a drive signal to the optical fiber transmission path, after a standby interval, to switch the optical switch in such a way that routing through the optical fiber transmission path for packet adding, dropping and passed-through would be different, depending on, as a result of the label discriminating step, whether an optical packet on the optical fiber path side is addressed to its own node apparatus, or there is no optical pass-packet and packets addressed to its own node apparatus are accumulated, or when an optical packet on the optical fiber path side is not addressed to its own node apparatus;

a label re-preparation step for preparing a new optical label when, as a result of the label discriminating step, the optical packet from the optical fiber transmission side is not addressed to its own node apparatus;

an optical label sending step for sending the optical label re-prepared in the label re-preparation step to the optical fiber transmission path through the optical switch;

a delaying step for delaying an optical packet arriving a specific time later than said separated optical label; and

an emitting step for outputting without any changes the optical packet that arrives after the delaying step to the optical fiber transmission path through the optical switch.

12. A method for protecting a label switched network for transferring packets between nodes according to address data included in label information, wherein a path code is attached to a frame of the label information to detect or correct errors in a transmission system so as to enable the nodes to monitor a line quality of the transmission system by monitoring the label information.

13. A method for protecting a label switched network according to

claim 12

, wherein said label switched network is an optical packet transfer network for transferring packets as optical packets;

and

in said optical packet transfer network, an optical packet is multiplexed with label information and transferred; and

said node extracts multiplexed label information only, and monitoring is performed by converting extracted label information to an electrical signal.

14. A method for protecting a label switched network according to

claim 12

, wherein said label switched network is a 2-fiber 1:

1 uni-directional type ring network and has a working path and a protection path as transmission paths, in which signals propagate uni-directionally but opposite to each other in the working path and the protection path so that, during normal operation, packets are directed only to the working path and each node monitors label information in the working path, and when an abnormal state is detected by a monitor, an abnormality report is issued to upper nodes in the working path by using one of either the working path, the protection path or an operational network; and

upon receiving an abnormality report, upper nodes divert packets to the protection path.

16. A method for protecting a label switched network according to

claim 12

, wherein said label switched network is a 2-fiber 1+1 ring network and has a working path and a protection path as transmission paths, in which signals propagate uni-directionally either in one direction or in opposite directions in the working path and the protection path according to destination node addresses so that, during normal operation, packets are directed to both the working path and the protection path, and a receiving terminal of a node receives packets from the working path and the label information is monitored by nodes;

and

upon detecting an abnormal state in label information by monitoring in the working path, the receiving terminal is switched to the protection path to receive packets.

17. A node apparatus for performing the method according to

claim 16

by transferring optical packets to be dropped from, added to or cut-through a ring network comprised by connecting a plurality of said node apparatuses in a ring shaped optical fiber transmission path, wherein said node apparatus has a working path and a protection path;

and each of said working path and said protection path is provided with;

an optical label extraction circuit section for extracting a label signal that contains at least address information relating to an optical packet in the optical fiber transmission path;

an optical label attaching circuit section for attaching a pass-label signal for an optical packet to be cut-through its own node and attaching an add-label signal for an optical packet to be added from its own node to the optical fiber transmission path;

an optical switch for switching optical packets so as to drop an optical packet in the optical fiber transmission path side addressed to its own node, or to add an optical packet from its own node to the optical fiber transmission path, or to cut-through an optical packet in the optical fiber transmission path side not addressed to its own node;

a label receiving circuit section for receiving label signals extracted by the optical label extraction circuit section;

a monitor for monitoring a path code included in a received label signal, and issuing a trigger signal to report an abnormal state when detected;

a control circuit section for issuing a packet send command signal to add an optical packet to the optical fiber transmission path by matching timing according to a label signal received, and receiving trigger signals issued by the monitor;

a packet editing sending circuit section for editing a plurality of packets addressed to node apparatuses having a common destination address into one packet and accumulating edited packets, and outputting a label signal containing at least node information on a destination node of a packet or routing information to the control circuit section;

not less than one packet sending circuit section for adding a packet sent from the packet editing sending circuit section to the optical fiber transmission path according to a packet send command issued from the control circuit section;

not less than one packet receiving circuit section for receiving optical packets addressed to its own node and dropped from the optical fiber transmission path;

a packet editing receiving circuit section for editing a packet received from the packet receiving circuit section into original pre-edited packets and accumulating original packets and transferring to user destinations;

and is further provided with;

not less than one terminating section for terminating data input from the user side and packetizing according to respective interfaces; and

a bridge/selector for sending packets sent from the terminating section to both the working path and the protection path during normal operation, and, during ring cut, sending packets sent from the terminating section by selecting either the working path or the protection path; and

a selector for transferring packets edited and accumulated by the packet editing receiving circuit section through either the working path or the protection path to users.

18. A method according to

claim 12

for protecting a label switched network, wherein said label switched network is a 2-fiber 1+1 ring network and has a working path and a protection path in the optical fiber transmission path, in which signals propagate uni-directionally, and during normal operation, said node sends packets through the working path and the protection path, and a receiving terminal of the node receives packets from both the working path and the protection path and compares and records packets received from both paths, and the label information is monitored by nodes;

and

when an abnormal state is detected by monitoring, the node switches the receiving terminal between the working path or the protection path for each packet.

19. A node apparatus according to

claim 17

for performing the method according to

claim 18

by having a packet comparison section for comparing and recording packets received in the packet editing receiving circuit section provided in the working path and the protection path.

20. A method according to

claim 12

, wherein said label switched network is a 4-fiber 1:

1 bi-directional label switched ring network, and has a working path and the protection path in the optical fiber transmission path, in which signals propagate in two opposing directions according to destination addresses of packets, and during normal operation, the node sends packets to the working path and the label information for the working path is monitored by nodes, and when an abnormal state is detected, the node diverts a packet addressed to a node that is not accessible because of the abnormal state through the protection path.

21. A node apparatus for performing the method according to

claim 20

by transferring optical packets to be dropped from, added to or cut-through a ring network comprised by connecting a plurality of said node apparatuses in a ring shaped optical fiber transmission path, wherein said node apparatus has a working path and a protection path which are bi-directional, and said working path is provided with:

an optical label extraction circuit section for extracting a label signal that contains at least address information relating to an optical packet in the optical fiber transmission path;

an optical label attaching circuit section for attaching a pass-label signal for an optical packet to be passed through its own node and attaching an add-label signal for an optical packet to be added from its own node to the optical fiber transmission path;

an optical switch for switching optical packets so as to drop an optical packet in the optical fiber transmission path side when the optical packet is addressed to its own node, or to add an optical packet from its own node to the optical fiber transmission path, or to cut-through an optical packet in the optical fiber transmission path side that is not addressed to its own node;

a label receiving circuit section for receiving a label signal extracted by the optical label extraction circuit section;

a monitor for monitoring a path code included in a received label signal, and issuing a trigger signal to report an abnormal state when detected;

a control circuit section for issuing a packet send command signal to add an optical packet to the optical fiber transmission path by matching timing according to a label signal received, and receiving trigger signals issued by the monitor;

not less than one terminating section for packetizing data input from the user side according to a relevant interface;

a packet editing sending circuit section for editing a plurality of packets addressed to node apparatuses having a common destination address into one packet and accumulating edited packets, and outputting a label signal containing at least node information on a destination node of a packet or routing information to the control circuit section;

not less than one packet sending circuit section for adding a packet sent from the packet editing sending circuit section to the optical fiber transmission path according to a packet send command issued from the control circuit section;

not less than one packet receiving circuit section for receiving optical packets addressed to its own node and dropped from the optical fiber transmission path;

a packet editing receiving circuit section for editing a packet received from the packet receiving circuit section into original pre-edited packets and accumulating original packets and transferring to user destinations; and

said protection path is provided with;

an optical label extraction section for extracting a label signal;

an optical switch for switching optical packets so as to drop an optical packet in the optical fiber transmission path side when the optical packet is addressed to its own node, or to add an optical packet from its own node to the optical fiber transmission path, or to cut-through an optical packet in the optical fiber path side that is not addressed to its own node;

an optical label receiving section for receiving label signals extracted by the optical label extraction circuit section;

a monitor for monitoring a path code included in a received label signal, and issuing a trigger signal to report an abnormal state when detected;

a control circuit section for receiving information contained in a received label signal and receiving trigger signals issued by the monitor;

not less than one packet receiving circuit section for receiving optical packets addressed to its own node apparatus and dropped from the optical fiber transmission path;

a packet editing receiving circuit section for separating a packet received from the packet receiving circuit section into original pre-edited packets and accumulating original packets and transferring to user destinations; and

for each pair of paths comprised by the working path and the protection path that are bi-directional and opposing, said node apparatus is further provided with;

a second optical switch controlled by the control circuit section to pass a packet through without any change to the working path of the optical fiber transmission path or to switch to the protection path of the optical fiber transmission path by reversing the direction of transmission; and

an input buffer provided in front of an input section of the second optical switch for connecting to the protection path of the optical fiber transmission path.

22. A method for protecting a label switched network according to

claim 12

, wherein said label switched network is a 4-fiber 1+1 ring network and has a working path and a protection path as transmission paths, in which signals propagate bi-directionally either in one direction or in opposite directions in the working path and the protection path according to destination node addresses so that, during normal operation, packets are directed to both the working path and the protection path, and a receiving terminal of a node receives packets from the working path and the label information is monitored by nodes;

and

upon detecting an abnormal state in label information in the working path by monitoring, the receiving terminal is switched to the protection path for receiving packets;

when an abnormal state is detected by monitoring in both the working path and the protection path, if the transfer direction in the working path is opposite to that in the protection path, the receiving terminal is switched to the protection path and a location of abnormality is notified to other nodes, and if the transfer direction in the working path is the same as that in the protection path, a node adjacent to an abnormal location drops all packets in the working path and the protection path temporarily, and the packets are transferred in respective opposite directions of the optical fiber transmission path to prevent loss of packets and a location of abnormality is notified to other nodes, and upon receiving a note specifying a location of abnormality from the node adjacent to the location of abnormality, each node determines a direction of sending packets so as to avoid the abnormal location.

23. A node apparatus for performing the method according to

claim 22

, by transferring optical packets to be dropped from, added to or cut-through a ring network comprised by connecting a plurality of said node apparatuses in a ring shaped optical fiber transmission path, wherein said node apparatus has a working path and a protection path;

and each of said working path and said protection path is provided with;

an optical label extraction circuit section for extracting a label signal that contains at least address information relating to an optical packet in the optical fiber transmission path;

an optical label attaching circuit section for attaching a pass-label signal for an optical packet to be passed through its own node and attaching an add-label signal for an optical packet to be added from its own node to the optical fiber transmission path;

an optical switch for switching optical packets so as to drop an optical packet in the optical fiber transmission path side when the optical packet is addressed to its own node, or to add an optical packet from its own node to the optical fiber transmission path, or to cut-through an optical packet in the optical fiber transmission path side that is not addressed to its own node;

a label receiving circuit section for receiving label signals extracted by the optical label extraction circuit section;

a monitor for monitoring a path code included in a received label signal, and issuing a trigger signal to report an abnormal state when detected;

a control circuit section for issuing a packet send command signal to add an optical packet to the optical fiber transmission path by matching timing according to a label signal received, and receiving trigger signals issued by the monitor;

a packet editing sending circuit section for editing a plurality of packets addressed to node apparatuses having a common destination address into one packet and accumulating edited packets, and outputting a label signal containing at least node information on a destination node of a packet or routing information to the control circuit section;

not less than one packet sending circuit section for adding a packet sent from the packet editing sending circuit section to the optical fiber transmission path according to a packet send command issued from the control circuit section;

not less than one packet receiving circuit section for receiving optical packets addressed to its own node and dropped from the optical fiber transmission path;

a packet editing receiving circuit section for editing a packet received from the packet receiving circuit section into original pre-edited packets and accumulating original packets and transferring to user destinations;

and is further provided with the optical label extraction circuit section, the optical label attaching circuit section, the optical switch, the label receiving circuit section, the monitor, the packet sending circuit section and the packet receiving circuit section, for use in both directions of packet transfer; and

further, not less than one terminating section for terminating data input from the user side and packetizing according to respective interfaces; and

a bridge/selector for sending packets sent from the terminating section to both the working path and the protection path during normal operation, and, during ring cut, sending packets sent from the terminating section by selecting either the working path or the protection path; and

a selector for transferring packets edited and accumulated by the packet editing receiving circuit section through either the working path or the protection path to users.

24. A method for protecting a label switched network of a 4-fiber 1+1 bi-directional type according to

claim 22

, wherein said node receives a packet from the working path and the protection path, and compares and records each packet, and the label signals are monitored by the node;

and

when an abnormal state is detected by monitoring, the node switches the receiving terminal between the working path or the protection path for each packet.

25. A node apparatus according to

claim 23

for performing the method for protecting a packet switching network recited in

claim 24

, wherein said node apparatus has a packet comparison circuit section for comparing and recording packets dropped from the working path and the protection path;

and

said selector determines for each packet whether to select the working path or the protection path according to a trigger signal output from the packet comparison circuit section.

15. A node apparatus for transferring optical packets to be dropped from, added to or cut-through a ring network comprised by connecting a plurality of said node apparatuses in a ring shaped optical fiber transmission path, wherein said node apparatus has a working path and a protection path;

and said working path is provided with;

an optical label extraction circuit section for extracting a label signal that contains at least address information relating to an optical packet in the optical fiber transmission path;

an optical label attaching circuit section for attaching a pass-label signal for an optical packet to be passed through its own node and attaching an add-label signal for an optical packet to be added from its own node to the optical fiber transmission path;

an optical switch for switching optical packets so as to drop an optical packet arriving in the optical fiber path side when the optical packet is addressed to its own node, or to add an optical packet from its own node to the optical fiber transmission path, or to cut-through an optical packet arriving in the optical fiber transmission path side that is not addressed to its own node;

a label receiving circuit section for receiving label signals extracted by the optical label extraction circuit section;

a monitor for monitoring a transmission code included in a received label signal, and issuing a trigger signal to report an abnormal state when detected;

a control circuit section for issuing a packet send command signal to add an optical packet to the optical fiber transmission path by matching timing according to a label signal received, and receiving trigger signals issued by the monitor;

not less than one terminating section for packetizing data input from the user side according to a relevant interface;

a packet editing sending circuit section for editing a plurality of packets addressed to node apparatuses having a common destination address into one packet and accumulating edited packets, and outputting a label signal containing at least node information on a destination node of a packet or routing information to the control circuit section;

not less than one packet sending circuit section for adding a packet sent from the packet editing sending circuit section to the optical fiber transmission path according to a packet send command issued from the control circuit section;

not less than one packet receiving circuit section for receiving optical packets addressed to its own node and dropped from the optical fiber transmission path;

a packet editing receiving circuit section for editing a packet received from the packet receiving circuit section into original pre-edited packets and accumulating original packets and transferring to user destinations;

according to user side interface, and said protection path is provided with;

an optical label extraction section for extracting a label signal;

an optical switch for switching optical packets so as to drop an optical packet arriving in the optical fiber transmission path side when the optical packet is addressed to its own node, or to cut-through an optical packet arriving in the optical fiber transmission path side that is not addressed to its own node;

an optical label receiving section for receiving label signals extracted by the optical label extraction circuit section;

a monitor for monitoring a transmission code included in a received label signal, and issuing a trigger signal to report an abnormal state when detected;

a control circuit section for receiving information contained in received label signals and trigger signals issued by the monitor;

not less than one packet receiving circuit section for receiving optical packets addressed to its own node apparatus and dropped from the optical fiber transmission path;

a packet editing receiving circuit section for separating a packet received from the packet receiving circuit section into original pre-edited packets and accumulating original packets and transferring to user destinations; and

the node apparatus is further provided with;

a second optical switch controlled by the control circuit section to pass a packet through without any change to the working path of the optical fiber transmission path or to switch to the protection path of the optical fiber transmission path by reversing the direction of transmission; and

an input buffer provided in front of an input section of the second optical switch for connecting to the protection path of the optical fiber transmission path.

28. A method for identifying a fault location of an optical switch disposed in an optical fiber transmission path formed by connecting add/drop multiplex type node apparatuses in a ring network for optical packets to be added to, or dropped from, or passed through the ring network, wherein at least one of the optical add/drop multiplex type node apparatuses is a master node apparatus that outputs, at given intervals, a label signal indicating only a designated optical node apparatus, having a specified address, is allowed to add optical packets to the optical fiber transmission path, and an optical node apparatus receiving the label signal recognizes according to the label that only said designated optical node apparatus as a dispatch node apparatus is allowed to add optical packets, wherein said master node apparatus outputs a pilot packet as a specific data train;

and

an add/drop multiplex type node apparatus receiving the pilot packet determines whether or not data have been received correctly by examining whether the received pilot packet represents the specific data train, and a normal/abnormal report is issued to the master node apparatus, and the master node apparatus determines which optical switch in the ring network is faulty according to the normal/abnormal report received.

29. A node apparatus, for transferring optical packets to be dropped from, added to or cut-through a ring network comprised by connecting a plurality of said node apparatuses in a ring shaped optical fiber transmission path, wherein said node apparatus has a working path and a protection path;

and each of said working path and said protection path is provided with;

an optical label extraction circuit section for extracting a label signal that contains at least address information relating to said optical packet in the optical fiber transmission path;

a monitor for monitoring extracted label signals and, if an abnormal state is found by monitoring, generating a trigger signal to notify that abnormality exists;

a control circuit section for discriminating whether an optical packet relating to an extracted label signal is to be dropped or passed through its own node apparatus according to the extracted label signal;

an optical label attaching circuit section for sending to the optical fiber transmission path a pass-label signal for an optical packet to be cut-through its own node, according to a result of discrimination by the control circuit section;

an optical switch for switching a path for optical packets according to a result of discrimination by the control circuit section;

a packet receiving circuit section for receiving optical packets dropped into its own node apparatus by way of the optical switch; and

further, in the working path, a sending circuit section is provided to send an optical packet input from the user side to the optical fiber transmission path through the optical switch, and the control circuit section switches the optical switch at same intervals as the optical packets sent through the sending circuit section; and

the control circuit section switches between the working path and the protection path according to a trigger signal issued by a monitor circuit section.

30. A node apparatus according to

claim 29

, wherein said node apparatus is a 1+1 type node apparatus that adds a same packet to both the working path and the protection path during normal operation, and the protection path has a sending circuit section for sending data input from the user side as optical packets to the optical fiber transmission path, and the control circuit section switches the optical switch at a same rate as optical packets output by the sending circuit section.

31. A node apparatus according to

claim 29

, wherein said node apparatus is a 2-fiber uni-directional node apparatus having one working path and one protection path in the optical fiber transmission path, and optical packets are transferred in one direction regardless of destination node apparatuses.

32. A node apparatus according to

claim 29

, wherein said node apparatus is a 4-fiber bi-directional node apparatus having two working paths and two protection paths in the optical fiber transmission path so that optical packets are sent in opposite directions and a direction of transfer is determined according to addresses of destination node apparatuses.

33. An optical packet compression circuit comprising:

an optical pulse generation section for generating optical pulses at Δ

T intervals;

an optical divider for separating optical pulses output from the optical pulse generation section into N pieces of signal lines, where N is a natural number;

a buffering circuit for temporarily storing serially input data and outputting N parallel trains;

N pieces of modulators, one modulator for each of N signal lines, for modulating optical signals output from the optical divider individually according to N pieces of data output from the buffering circuit;

an optical delay line provided in a back stage of the modulator in each signal line for delaying output signals of the modulator by an amount equal to a whole multiple of Δ

t; and

an optical coupler for outputting modulated optical pulses so that each optical pulse is shifted by an interval Δ

t by means of the optical delay line.

34. An optical packet compression circuit according to

claim 33

, wherein provided are:

a plurality of input signal lines;

a plurality of buffering circuits corresponding to each of the input signal lines;

a read control circuit for outputting read-signals so as to successively read data from the plurality of buffering circuits; and

N pieces of OR circuits for selecting data so as to drive respective modulators in association with the plurality of buffering circuits.

35. An optical packet compression circuit according to

claim 34

, wherein said buffering circuit has a serial/parallel conversion circuit for converting serial input data into N parallel trains and a memory for temporarily storing data and outputting the data according to signals from the read control circuit;

and

said OR circuit is a logical sum circuit.

36. An optical packet compression circuit according to

claim 34

, wherein said buffering circuits are provided in N pieces so that N-lines of input data trains are compressed and output as one line.

37. An optical packet decompression circuit comprising:

an optical serial/parallel conversion circuit for converting continual input optical pulse signals into N parallel trains of optical pulses, where N is a natural number;

N pieces of photo detectors for optical/electrical conversion of respective optical pulse signals produced by the serial/parallel conversion circuit;

not less than one start-bit detection circuit for detecting a start-bit of electrical signals output from the N pieces of photo detectors;

N pieces of switches for directing electrical signals output from the N pieces of photo detectors to respective buffers;

N² pieces of memories for temporarily storing each bit of N pieces of electrical signals directed to N pieces of switches;

a read circuit for generating a read-signal, when a start-bit is detected by a start-bit detection circuit-1, for each bit of the N² pieces of memories so that N² pieces of signals are successively read out from the memories, beginning with a memory corresponding to said start-bit detection circuit-1; and

N pieces of multiplexing circuit sections for multiplexing each group of N data read from the N² pieces of memories according to a read-signal, and outputting resulting groups of multiplexed signals to output signal lines.

38. An optical packet decompression circuit according to

claim 37

, wherein said serial/parallel conversion circuit is comprised by an OTDM/WDM conversion circuit for converting pulses in continually input optical pulses located at different time positions into different wavelengths, and a waveguide for separating each wavelength of a multiplexed signal output from the OTDM/WDM conversion circuit into N waves.

39. An optical packet decompression circuit comprising:

an OTDM/WDM conversion circuit for converting pulses in continually input optical pulses located at different time positions into different wavelengths; and

a dispersive medium for receiving signals from the OTDM/WDM conversion circuit, and generating different values of time delay according to signal wavelengths.

40. An optical packet decompression circuit according to

claim 39

, wherein said dispersive medium is comprised by a chirped fiber grating to reflect input light signals at different delay times according to input wavelengths, and an optical circuit to direct an optical signal output from the OTDM/WDM conversion circuit to the chirped fiber grating and to direct an optical signal reflected from the chirped fiber grating to an output side.

41. An optical decompression circuit comprised by connecting decompression circuits, each of which is according to

claim 39

, in series, so that each stage of optical decompression circuit divides an input optical pulse train into a plurality of partial pulse trains so as to result in an input optical pulse signal being divided in each stage into partial trains of decreasing units by the plurality of stages connected in series.