Optical ring networks having node-to-node optical communication channels for carrying data traffic

Abstract

Techniques, apparatus and systems for optical communications, including fiber ring networks with protection switching to maintain optical communications when an optical failure occurs and to automatically revert to normal operation when the optical failure is corrected, fiber ring networks that provide a circulating optical probe signal at an optical probe wavelength within the gain spectral range of optical amplifiers used in a fiber ring network to detect an optical failure, and fiber ring networks that support broadcast-and-select optical WDM signals carrying communication traffic to the optical ring nodes without regeneration at each optical ring node and one or more overlaid in-band node-to-node optical signals carrying communication traffic with regeneration at each node.

1 . An optical communication system, comprising:
 a plurality of optical ring nodes connected to form an optical ring which support (1) broadcast-and-select optical WDM signals carrying communication traffic to the optical ring nodes without regeneration at each optical ring node, and (2) at least one node-to-node optical WDM signal carrying communication traffic from one optical ring node to an adjacent optical ring node by regeneration at each optical ring node, wherein the node-to-node optical WDM signal is at a wavelength different from wavelengths of the broadcast-and-select optical WDM signals; and   a plurality of optical amplifiers coupled in the optical ring and operable to amplify light in a gain spectral range covering optical wavelengths of the broadcast-and-select optical WDM signals.   
     
     
         2 . The system as in  claim 1 , comprising:
 an optical probe transmitter coupled to the optical ring network to supply to the optical ring network an optical probe signal at a probe wavelength which is inside or near one end of the gain spectral range to obtain a sufficient optical gain from the optical amplifiers to sustain a detectable signal level;   a probe monitor in at least one optical ring node to split a portion of the optical probe signal and to monitor the optical probe signal to detect an optical failure in the optical ring network; and   a protection switch in the optical ring network to create a default optical break point when the probe monitor indicates that there is no optical failure in the optical ring network and to close the default optical break point when the probe monitor indicates that there is an optical failure,   wherein the optical ring network is responsive to a status of the monitored optical probe signal to control the protection switch and the optical ring nodes to sustain communications in the optical ring network outside a location of the optical failure and to restore communications in the optical ring network after the optical failure is repaired.   
     
     
         3 . The system as in  claim 1 , wherein the at least one node-to-node optical WDM signal is within the gain spectral range of the optical amplifiers. 
     
     
         4 . The system as in  claim 1 , wherein the at least one node-to-node optical WDM signal is outside the gain spectral range of the optical amplifiers. 
     
     
         5 . The system as in  claim 1 , wherein the optical ring includes first and second fibers to connect two adjacent nodes to carry optical traffic in opposite directions, respectively. 
     
     
         6 . The system as in  claim 5 , wherein each node comprises:
 an optical add and drop module coupled to the first and second fibers to produce one or more of the broadcast-and-select optical WDM signals and to split a fraction of light in the broadcast-and-select optical WDM signals for detection while transmitting rest of the light in the broadcast-and-select optical WDM signals;   a first node-to-node optical module that is coupled to the first and second fibers downstream in the first fiber from the optical add and drop module and comprises:
 a first node-to-node optical transmitter to produce the node-to-node optical WDM signal for the first fiber to a downstream optical node in the first fiber; 
 a first optical add coupler coupled to the first fiber to direct the node-to-node optical WDM signal into the first fiber towards the downstream optical node in the first fiber; 
 a first optical drop coupler coupled to the second fiber upstream to the optical add and drop module to selectively couple light of the node-to-node optical WDM signal from an upstream optical node in the second fiber out of the second fiber while transmitting light of other wavelengths including the broadcast-and-select optical WDM signals; and 
 a first optical receiver coupled to receive the node-to-node optical WDM signal from the first optical drop coupler; and 
   a second node-to-node optical module that is coupled to the first and second fibers upstream in the first fiber to the optical add and drop module and comprises:
 a second node-to-node optical transmitter to produce the node-to-node optical WDM signal for the second fiber to a downstream optical node in the second fiber; 
 a second optical add coupler coupled to the second fiber to direct the node-to-node optical WDM signal into the second fiber towards the downstream optical node in the second fiber; 
 a second optical drop coupler coupled to the first fiber upstream to the optical add and drop module to selectively couple light of the node-to-node optical WDM signal from an upstream optical node in the first fiber out of the first fiber while transmitting light of other wavelengths including the broadcast-and-select optical WDM signals; and 
 a second optical receiver coupled to receive the node-to-node optical WDM signal from the second optical drop coupler. 
   
     
     
         7 . The system as in  claim 6 , wherein each node comprises an electronic switching protection mechanism to provide switching for the node-to-node communication traffic. 
     
     
         8 . The system as in  claim 6 , comprising:
 an optical supervision channel (OSC) mechanism operable to produce an OSC signal at an OSC wavelength between two adjacent two optical ring nodes in each of the first and second fibers to communicate information on the ring network other than data traffic, the OSC mechanism comprising:   in each optical ring node,   a first OSC optical module that is coupled to the first and second fibers downstream in the first fiber from the optical add and drop module and comprises:
 a first OSC optical transmitter to produce the OSC signal for the first fiber to a downstream optical node in the first fiber; 
 a first OSC add coupler coupled to the first fiber to direct the OSC signal into the first fiber towards the downstream optical node in the first fiber; 
 a first OSC drop coupler coupled to the second fiber upstream to the optical add and drop module to selectively couple light of the OSC optical WDM signal from an upstream optical node in the second fiber out of the second fiber while transmitting light of other wavelengths; and 
 a first OSC receiver coupled to receive the OSC signal from the first OSC drop coupler; and 
   a second OSC optical module that is coupled to the first and second fibers upstream in the first fiber to the optical add and drop module and comprises:
 a second OSC transmitter to produce the OSC signal for the second fiber to a downstream optical node in the second fiber; 
 a second OSC add coupler coupled to the second fiber to direct the OSC signal into the second fiber towards the downstream optical node in the second fiber; 
 a second OSC drop coupler coupled to the first fiber upstream to the optical add and drop module to selectively couple light of the OSC signal from an upstream optical node in the first fiber out of the first fiber while transmitting light of other wavelengths; and 
 a second OSC receiver coupled to receive the OSC signal from the second optical drop coupler. 
   
     
     
         9 . The system as in  claim 8 , comprising:
 an optical probe transmitter coupled to the optical ring network to supply to the optical ring network an optical probe signal at a probe wavelength which is inside or near one end of the gain spectral range to obtain a sufficient optical gain from the optical amplifiers to sustain a detectable signal level;   a probe monitor in at least one optical ring node to split a portion of the optical probe signal and to monitor the optical probe signal to detect an optical failure in the optical ring network; and   a protection switch in the optical ring network to create a default optical break point when the probe monitor indicates that there is no optical failure in the optical ring network and to close the default optical break point when the probe monitor indicates that there is an optical failure,   wherein the optical ring network is responsive to both a status of the monitored optical probe signal and a status of the OSC signal to control the protection switch and the optical ring nodes to sustain communications in the optical ring network outside a location of the optical failure and to restore communications in the optical ring network after the optical failure is repaired.   
     
     
         10 . The system as in  claim 5 , wherein each node comprises:
 an optical add and drop module coupled to the first and second fibers to produce one or more of the broadcast-and-select optical WDM signals and to split a fraction of light in the broadcast-and-select optical WDM signals for detection while transmitting rest of the light in the broadcast-and-select optical WDM signals;   a first node-to-node optical transmitter to produce the node-to-node optical WDM signal at a first node-to-node WDM wavelength;   a first optical coupler to receive the node-to-node optical WDM signal from the first node-to-node optical transmitter and to split the node-to-node optical WDM signal into a first part of the node-to-node optical WDM signal and a second part of the node-to-node optical WDM signal;   a second node-to-node optical transmitter to produce a second node-to-node optical WDM signal at a second node-to-node WDM wavelength different from the first node-to-node WDM wavelength;   a second optical coupler to receive the second node-to-node optical WDM signal from the second node-to-node optical transmitter and to split the second node-to-node optical WDM signal into a first part of the second node-to-node optical WDM signal and a second part of the second node-to-node optical WDM signal;   a first optical add module to combine the first part of the node-to-node optical WDM signal and the first part of the second node-to-node optical WDM signal into a first add signal;   a second optical add module to combine the second part of the node-to-node optical WDM signal and the second part of the second node-to-node optical WDM signal into a second add signal;   a first optical add coupler coupled to the first fiber to direct the first add signal to the first fiber;   a second optical add coupler coupled to the second fiber to direct the second add signal to the second fiber;   a first optical drop coupler coupled to the first fiber upstream from the first optical add coupler to selectively couple light of the node-to-node optical WDM signal and the second node-to-node optical WDM signal out of the first fiber while transmitting light of the broadcast-and-select optical WDM signals;   a first optical drop module to separate the light of the node-to-node optical WDM signal and the second node-to-node optical WDM signal from the first optical drop coupler into a first drop part of the node-to-node optical WDM signal and a first drop part of the second node-to-node optical WDM signal;   a second optical drop coupler coupled to the second fiber upstream from the second optical add coupler to selectively couple light of the node-to-node optical WDM signal and the second node-to-node optical WDM signal out of the second fiber while transmitting light of the broadcast-and-select optical WDM signals;   a second optical drop module to separate the light of the node-to-node optical WDM signal and the second node-to-node optical WDM signal from the second optical drop coupler into a second drop part of the node-to-node optical WDM signal and a second drop part of the second node-to-node optical WDM signal; and   a first optical receiver to receive the first and second drop parts of the node-to-node optical WDM signal; and   a second optical receiver to receive the first and second drop parts of the second node-to-node optical WDM signal.   
     
     
         11 . The system as in  claim 10 , wherein each node comprises an electronic switching protection mechanism to provide switching for the node-to-node communication traffic. 
     
     
         12 . The system as in  claim 1 , wherein:
 the optical ring nodes comprise reconfigurable optical add and drop multiplexers each operable to add or drop one or more of optical WDM channels; and   the node-to-node optical WDM signal is at a WDM wavelength that is different from WDM wavelengths of the optical WDM channels of the reconfigurable optical add and drop multiplexers.   
     
     
         13 . An optical communication system, comprising:
 a plurality of optical ring nodes connected to form an optical ring having a first optical ring path to carry light through the optical ring nodes along a first direction and a second optical ring path to carry light through the optical ring nodes along a second, opposite direction,   wherein the optical ring is configured to support (1) broadcast-and-select optical WDM signals carrying communication traffic to the optical ring nodes without regeneration at each optical ring node in each of the first and second optical ring paths, and (2) at least one node-to-node optical WDM signal carrying communication traffic from one optical ring node to an adjacent optical ring node by regeneration at each optical ring node in each of the first and second optical ring paths, and   wherein each ring node comprises:   a broadcast-and-select add and drop module to produce at least one of the broadcast-and-select optical WDM signals and to split a fraction of light in the broadcast-and-select optical WDM signals for detection while transmitting rest of the light in the broadcast-and-select optical WDM signals;   a node-to-node optical transmitter to produce the node-to-node optical WDM signal;   an optical coupler to receive the node-to-node optical WDM signal from the node-to-node optical transmitter and to split the node-to-node optical WDM signal into a first node-to-node optical WDM signal and a second node-to-node optical WDM signal;   a first optical add coupler coupled to the first optical ring path to direct the first node-to-node optical WDM signal to the first optical ring path;   a second optical add coupler coupled to the second optical ring path to direct the second node-to-node optical WDM signal to the second optical ring path; a first optical drop coupler coupled to the first optical ring path upstream from the first optical add coupler to selectively couple light of the first node-to-node optical WDM signal out of the first optical ring path while transmitting light of the broadcast-and-select optical WDM signals;   a second optical drop coupler coupled to the second optical ring path upstream from the second optical add coupler to selectively couple light of the second node-to-node optical WDM signal out of the second optical ring path while transmitting light of the broadcast-and-select optical WDM signals; and   an optical receiver coupled to receive the first and second node-to-node optical WDM signals from the first and second optical drop couplers.   
     
     
         14 . The system as in  claim 15 , comprising:
 an optical probe transmitter coupled to the optical ring network to supply to the optical ring network an optical probe signal at a probe wavelength which is different from wavelengths of the broadcast-and-select optical WDM signals and the node-to-node optical WDM signal;   a probe monitor in at least one optical ring node to split a portion of the optical probe signal and to monitor the optical probe signal to detect an optical failure in the optical ring network; and   a protection switch in the optical ring network to create a default optical break point when the probe monitor indicates that there is no optical failure in the optical ring network and to close the default optical break point when the probe monitor indicates that there is an optical failure,   wherein the optical ring network is responsive to a status of the monitored optical probe signal to control the protection switch and the optical ring nodes to sustain communications in the optical ring network outside a location of the optical failure and to restore communications in the optical ring network after the optical failure is repaired.   
     
     
         15 . The system as in  claim 14 , comprising:
 an optical supervision channel (OSC) mechanism operable to produce an OSC signal at an OSC wavelength between two adjacent two optical ring nodes in each of the first and second fibers to communicate information on the ring network other than data traffic, and   wherein the optical ring network is responsive to a status of the OSC signal, in addition to the status of the monitored optical probe signal, to control the protection switch and the optical ring nodes to sustain communications in the optical ring network outside a location of the optical failure and to restore communications in the optical ring network after the optical failure is repaired.   
     
     
         16 . The system as in  claim 13 , wherein:
 the optical ring nodes comprise reconfigurable optical add and drop multiplexers each operable to add or drop one or more of optical WDM channels; and   the node-to-node optical WDM signal is at a WDM wavelength that is different from WDM wavelengths of the optical WDM channels of the reconfigurable optical add and drop multiplexers.   
     
     
         17 . A method for optical communication in a ring network, comprising:
 using broadcast-and-select optical WDM signals at different wavelengths to carry communication traffic to optical ring nodes in the ring network, each optical ring node splitting a fraction of the broadcast-and-select optical WDM signals for detection while transmitting rest of light of the broadcast-and-select optical WDM signals to a next optical ring node;   using at least one node-to-node optical WDM signal carrying node-to-node communication traffic from one optical ring node to an adjacent optical ring node by regeneration at each optical ring node, wherein the node-to-node optical WDM signal is at a wavelength different from wavelengths of the broadcast-and-select optical WDM signals;   designating each broadcast-and-select optical WDM signal to a selected optical ring node for sending data from the selected optical ring node to one or more other optical ring nodes; and   operating the optical ring nodes to share a bandwidth of the node-to-node optical WDM signal to transmit data from one optical ring node to one or more other optical ring nodes through the node-to-node communication traffic.   
     
     
         18 . The method as in  claim 17 , comprising:
 selecting an optical ring node that has a node traffic less than a threshold value to transmit data to one or more other optical ring nodes through the shared bandwidth of the node-to-node optical WDM signal only without designating a broadcast-and-select optical WDM signal to the selected optical ring node.   
     
     
         19 . The method as in  claim 17 , comprising:
 selecting an optical ring node that has a node traffic higher than a threshold value to designate a broadcast-and-select optical WDM signal to the selected optical ring node for transmitting data to one or more other optical ring nodes.   
     
     
         20 . The method as in  claim 18 , comprising:
 operating the selected optical ring node to use, in addition to the designated broadcast-and-select optical WDM signal, the shared bandwidth of the node-to-node optical WDM signal to transmit data to one or more other optical ring nodes.   
     
     
         21 . The method as in  claim 17 , comprising:
 selecting an optical ring node, based on a level of quality of service or a level of communication latency associated with the selected optical ring node, to designate a broadcast-and-select optical WDM signal to the selected optical ring node for transmitting data to one or more other optical ring nodes.   
     
     
         22 . The method as in  claim 21 , comprising:
 operating the selected optical ring node to use, in addition to the designated broadcast-and-select optical WDM signal, the shared bandwidth of the node-to-node optical WDM signal to transmit data to one or more other optical ring nodes.   
     
     
         23 . The method as in  claim 17 , comprising:
 in the optical ring network, circulating an optical probe signal at a probe wavelength which is different from wavelengths of the broadcast-and-select optical WDM signals and the node-to-node optical WDM signal;   in at least one optical ring node, splitting a portion of the optical probe signal to monitor the optical probe signal to detect an optical failure in the optical ring network; and   operating a protection switch in the optical ring network to create a default optical break point when the optical probe signal indicates that there is no optical failure in the optical ring network and to close the default optical break point when the optical probe signal indicates that there is an optical failure.   
     
     
         24 . The method as in  claim 23 , comprising:
 operating an optical supervision channel (OSC) mechanism to produce an OSC signal at an OSC wavelength between two adjacent two optical ring nodes to communicate information on the ring network other than data traffic; and   operating the optical ring network in response to a status of the OSC signal, in addition to the status of the monitored optical probe signal, to control the protection switch and the optical ring nodes.   
     
     
         25 . An optical communication system, comprising:
 a plurality of optical ring nodes connected to form an optical ring which support (1) broadcast-and-select optical WDM signals carrying communication traffic to the optical ring nodes without regeneration at each optical ring node, and (2) at least one node-to-node optical WDM signal carrying communication traffic from one optical ring node to an adjacent optical ring node by regeneration at each optical ring node, wherein the node-to-node optical WDM signal is at a wavelength different from wavelengths of the broadcast-and-select optical WDM signals; and   a central node connected to the optical ring and structured to comprise an optical-to-electrical-to-optical (OEO) block which converts received broadcast-and-select optical WDM signals into electrical signals and to regenerate the broadcast-and-select optical WDM signals that travel to the optical ring nodes, the central node structured to support the one node-to-node optical WDM signal carrying communication traffic from an adjacent optical ring node to another adjacent optical ring node by regeneration of the one node-to-node optical WDM signal.   
     
     
         26 . The system as in  claim 25 , comprising:
 a plurality of optical amplifiers coupled in the optical ring and operable to amplify light in a gain spectral range covering optical wavelengths of the broadcast-and-select optical WDM signals.   
     
     
         27 . The system as in  claim 25 , wherein:
 the optical ring includes first and second fibers to connect two adjacent nodes to carry optical traffic in opposite directions, respectively, and   the system comprising:   an optical supervision channel (OSC) mechanism operable to produce an OSC signal at an OSC wavelength between two adjacent two optical ring nodes in each of the first and second fibers to communicate information on the ring network other than data traffic, the OSC mechanism comprising:   in each optical ring node and the central node,   a first OSC optical module that is coupled to the first and second fibers downstream in the first fiber from the optical add and drop module and comprises:
 a first OSC optical transmitter to produce the OSC signal for the first fiber to a downstream optical node in the first fiber; 
 a first OSC add coupler coupled to the first fiber to direct the OSC signal into the first fiber towards the downstream optical node in the first fiber; 
 a first OSC drop coupler coupled to the second fiber upstream to the optical add and drop module to selectively couple light of the OSC optical WDM signal from an upstream optical node in the second fiber out of the second fiber while transmitting light of other wavelengths; and 
 a first OSC receiver coupled to receive the OSC signal from the first OSC drop coupler; and 
   a second OSC optical module that is coupled to the first and second fibers upstream in the first fiber to the optical add and drop module and comprises:
 a second OSC transmitter to produce the OSC signal for the second fiber to a downstream optical node in the second fiber; 
 a second OSC add coupler coupled to the second fiber to direct the OSC signal into the second fiber towards the downstream optical node in the second fiber; 
 a second OSC drop coupler coupled to the first fiber upstream to the optical add and drop module to selectively couple light of the OSC signal from an upstream optical node in the first fiber out of the first fiber while transmitting light of other wavelengths; and 
 a second OSC receiver coupled to receive the OSC signal from the second optical drop coupler. 
   
     
     
         28 . The system as in  claim 27 , wherein the central node is responsive to a status of the OSC signal to control a protection switching mechanism within the OEO block to sustain communications in the optical ring network when the OSC signal indicates an optical failure. 
     
     
         29 . The system as in  claim 25 , wherein:
 each optical ring node comprises a reconfigurable optical add and drop multiplexer; and   the node-to-node optical WDM signal is at a WDM wavelength that is different from WDM wavelengths of the optical WDM channels of the reconfigurable optical add and drop multiplexers.