OSNR Model For Optical Engineering Rules Used In A Planning Tool

Abstract

Increasing data rates in next-generation optical networks requires a change in the type of optical modulation used to encode optical signals carried by the optical networks. Different types of optical modulation incur different optical impairments, which may degrade the fidelity of the optical signals by reducing the optical signal-to-noise ratio (OSNR). A method or corresponding apparatus in an example embodiment of the present invention provides a planning tool for deploying an optical network in a manner based on the optical modulation that reduces the cost and complexity of the deployed network. In one embodiment, the disclosed planning tool may adjust a model of the optical network to be deployed by changing the topology and/or the number and/or type of optical network elements in response to optical impairments for a given optical modulation.

What is claimed is: 
     
         1 . A method of planning deployment of an optical network, the method comprising:
 enabling modeling of an optical network, including a model representing a topology of optical network elements (ONEs), models of ONEs, and models of optical signals with optical modulation, and enabling selection of an optical modulation to be used to support communications between respective ONEs on the optical network;   computing optical signal-to-noise ratio (OSNR) penalties as a function of the optical modulation selected;   iteratively adjusting the model of the optical network to change the OSNR penalties in a manner known to enable detection of the optical signals to support the communications between the ONEs; and   reporting indications of the model of the optical network.   
     
     
         2 . The method of  claim 1  wherein enabling modeling of the optical network includes enabling selection of an on/off keying optical modulation or a differential quadrature phase-shift keying optical modulation to be used to support communications between respective ONEs on the optical network. 
     
     
         3 . The method of  claim 1  wherein enabling modeling of the optical network includes models of any of optical amplifiers, transponders, optical regenerators, and reconfigurable optical add/drop multiplexers. 
     
     
         4 . The method of  claim 1  wherein computing the OSNR penalties includes computing the OSNR as a function of the optical modulation selected and as a function of optical impairments associated with the model of the optical network. 
     
     
         5 . The method of  claim 1  wherein computing OSNR penalties includes calculating optical impairments due to any of chromatic dispersion, polarization mode dispersion, four-wave mixing, self-phase modulation, and cross-phase modulation. 
     
     
         6 . The method of  claim 5  wherein computing OSNR penalties includes calculating lower optical impairments due to polarization mode dispersion for differential quadrature phase-shift keying than for on/off keying and calculating higher optical impairments due to four-wave mixing, self-phase modulation, and cross-phase modulation for differential quadrature phase-shift keying than for on/off keying. 
     
     
         7 . The method of  claim 1  wherein iteratively adjusting the model of the optical network includes:
 replacing models of a first type of ONE with models of a second type of ONE; 
 adding or removing models of nodes from the topology of ONEs, including adding models of regenerating lasers and receivers between transmission end points; 
 bounding the OSNR penalties to remaing below a threshold throughout the model of the optical network; or 
 enabling any combination of thereof. 
 
     
     
         8 . The method of  claim 1  wherein reporting indications of the model of the optical network includes reporting indications of the topology of ONEs indications of the ONEs. 
     
     
         9 . The method of  claim 1  wherein reporting indications of the model of the optical network includes reporting of changes in the topology of ONEs and indications of changes in the ONEs. 
     
     
         10 . The method of  claim 1  wherein reporting indications of the model of the optical network includes reporting after a given number of iterations, the number of iterations being selected from: a fixed number, a convergence of at least a subset of the OSNR penalties, a number performed in a period of time, and a user-determined number. 
     
     
         11 . An apparatus to plan deployment of an optical network, the apparatus comprising:
 a modeling unit configured to enable a model of an optical network including a model representing a topology of optical network elements (ONEs), models of ONEs, and models of optical signals with optical modulation, and to enable selection of an optical modulation to be used to support communications between respective ONEs on the optical network;   a computing unit configured to compute optical signal-to-noise ratio (OSNR) penalties as a function of the optical modulation selected;   an adjustment unit configured to iteratively adjust the model of the optical network to change the OSNR penalties in a manner known to enable detection of the optical signals to support the communications between the ONEs; and   a reporting unit configured to report indications of the model of the optical network.   
     
     
         12 . The apparatus of  claim 11  wherein the modeling unit is further configured to enable selection of an on/off keying optical modulation or a differential quadrature phase-shift keying optical modulation to be used to support communications between respective ONEs on the optical network. 
     
     
         13 . The apparatus of  claim 11 , wherein the modeling unit is further configured to enable models of any of optical amplifiers, transponders, optical regenerators, and reconfigurable optical add/drop multiplexers. 
     
     
         14 . The apparatus of  claim 11  wherein the computing unit is further configured to compute the OSNR penalties as the function of the optical modulation selected and as a function of optical impairments associated with the model of the optical network. 
     
     
         15 . The apparatus of  claim 11  wherein the computing unit is further configured to calculate optical impairments due to any of chromatic dispersion, polarization mode dispersion, four-wave mixing, self-phase modulation, and cross-phase modulation. 
     
     
         16 . The apparatus of  claim 15  wherein the computing unit is further configured to calculate lower optical impairments due to polarization mode dispersion for differential quadrature phase-shift keying than for on/off keying, and to calculate higher optical impairments due to four-wave mixing, self-phase modulation, and cross-phase modulation for differential quadrature phase-shift keying than for on/off keying. 
     
     
         17 . The apparatus of  claim 11  wherein the adjustment unit is further configured to:
 replace models of a first type of ONE with models of a second type of ONE; 
 add or remove nodes from the topology of ONEs, including adding regenerating lasers and receivers between transmission end points of the optical network; 
 bound the OSNR penalties to remain below a threshold throughout the model of the optical network; or 
 any combination thereof 
 
     
     
         18 . The apparatus of  claim 11  wherein the reporting unit is further configured to report indications of the topology of ONEs and indications of the ONEs. 
     
     
         19 . The apparatus of  claim 11  wherein the reporting unit is further configured to report indications of changes in the topology of ONEs and indications of changes in the ONEs. 
     
     
         20 . The apparatus of  claim 11  wherein the reporting unit is further configured to report after a given number of iterations, the number of iterations being selected from: a fixed number, a convergence of at least a subset of the OSNR penalties, a number performed in a period of time, and a user-determined number. 
     
     
         21 . A computer program product including a computer-readable medium having a computer-readable program, the computer-readable program, when executed by a computer, causes the computer to:
 model an optical network including enabling a model representing a topology of optical network elements (ONEs), models of ONEs, and models of optical signals with optical modulation, and selection of an optical modulation to be used to support communications between respective ONEs on the optical network;   compute optical signal-to-noise ratio (OSNR) penalties as a function of the optical modulation selected;   iteratively adjust the model of the optical network in an attempt to change the OSNR penalties in a manner known to enable detection of the optical signals to support communications between ONEs; and   report indications of the model of the optical network.