Source: http://www.google.com/patents/US20030099014?ie=ISO-8859-1&dq=5179747
Timestamp: 2014-03-08 07:14:30
Document Index: 735817948

Matched Legal Cases: ['art 800', 'art 800', 'art 800', 'art 800', 'art 800', 'art 800']

Patent US20030099014 - System and method for optimized design of an optical network - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsA method of designing a network configuration comprising designating placement of a plurality of network components within a first network configuration having a plurality of sites and a respective physical link interconnecting two of the plurality of sites, modeling conveyance of an optical signal along...http://www.google.com/patents/US20030099014?utm_source=gb-gplus-sharePatent US20030099014 - System and method for optimized design of an optical networkAdvanced Patent SearchPublication numberUS20030099014 A1Publication typeApplicationApplication numberUS 10/133,695Publication dateMay 29, 2003Filing dateApr 25, 2002Priority dateApr 26, 2001Publication number10133695, 133695, US 2003/0099014 A1, US 2003/099014 A1, US 20030099014 A1, US 20030099014A1, US 2003099014 A1, US 2003099014A1, US-A1-20030099014, US-A1-2003099014, US2003/0099014A1, US2003/099014A1, US20030099014 A1, US20030099014A1, US2003099014 A1, US2003099014A1InventorsWill Egner, Vinay Mallapu, Yindong ZhengOriginal AssigneeEgner Will A., Mallapu Vinay Kumar Reddy, Yindong ZhengExport CitationBiBTeX, EndNote, RefManReferenced by (54), Classifications (15), Legal Events (4) External Links: USPTO, USPTO Assignment, EspacenetSystem and method for optimized design of an optical networkUS 20030099014 A1Abstract A method of designing a network configuration comprising designating placement of a plurality of network components within a first network configuration having a plurality of sites and a respective physical link interconnecting two of the plurality of sites, modeling conveyance of an optical signal along a light path between at least two sites of the first network configuration, the modeled optical signal comprising a calculated signal attribute at a plurality of locations, the value of the calculated signal attribute at any of the plurality of locations dependent upon designation of a set of the network components included within the light path, determining a position for potential placement of at least one of an amplification stage and a regeneration stage within the first network configuration is provided. Images(12) Claims(38)
DETAILED DESCRIPTION OF THE DRAWINGS [0029] The preferred embodiment of the present invention and its advantages are best understood by referring to FIGS. 1 through 21 of the drawings, like numerals being used for like and corresponding parts of the various drawings. [0030] The computer-aided optical network design of the subject invention facilitates network design by minimizing wavelength usage, optimizing waveband grouping and sequencing, optimizing fiber level switching, and modeling light path characteristics and corresponding signal losses to facilitate a network configuration featuring the most economical cost for specified network performance requirements. By minimizing wavelength usage, equipment costs at the optical layer are reduced by limiting the number of underlying lasers and detectors as well as the requisite common equipment. Additionally, effective reuse of wavelength assignments increases bandwidth utilization thereby allowing for increased capacity available for future services provisioned on the network. Increasing waveband reuse can reduce common equipment costs and provide an increase in overall network capacity. For example, avoiding traffic assignments to wavebands with wavelengths (also referred to herein as service channels and lambdas λ) that must be subjected to optical-to-electrical-to-optical conversions (OEO), such as is required when transmitting wavelengths along an unclear light path, with wavelength assignments that are not subject to similar conversions, OEO and/or optical line amplifier (OLA) equipment quantities may be reduced. Moreover, automated placement of amplification and/or regeneration components within the network design is facilitated by modeling optical signal deterioration that may include signal loss, noise accumulation, and dispersion effects according to an embodiment of the present invention. [0031] The present invention is implemented as an optimization algorithm 10, or program, comprised of one or more sets of computer-executable instructions that is provided with various inputs 20-22 specifying requirements of a particular network design and that provides various outputs upon execution of algorithm 10, as illustrated in the block diagram of FIG. 1. In the context of this document, a �computer-readable medium� can be any means that can contain, store, communicate, propagate or transport the program for use by or in connection with the instruction execution system, apparatus, or device. The computer-readable medium can be, for example, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semi-conductor system, apparatus, device, or propagation medium now known or later developed, including (a non-exhaustive list): an electrical connection having one or more wires, a portable computer diskette, a random access memory (RAM), a read-only memory (ROM), an erasable, programmable, read-only memory (EPROM or Flash memory), an optical fiber, and a portable compact disk read-only memory (CDROM). The instruction execution apparatus may be any conventional computer system featuring any one of various commercially available processing unit(s). [0032] Inputs 20-22 provided to algorithm 10 may comprise a traffic input 20 defining traffic requirements of the network, a connection attribute input 21 comprising physical attributes of the network, and a resource input 22 comprised of resource specifications of the network. Each input 20-22 may comprise one or more data elements that are conveyed to algorithm 10. For example, traffic input 20 may include one or more data elements defining an average demand, a service type, a peak demand, and/or a quality of service (QoS) parameter such as delay, blocking and/or availability metrics. Attribute input 21 may comprise a plurality of data elements as well, such as a site name, location, and fiber connectivity that defines how various network elements are interconnected. Likewise, resource input 22 may comprise a plurality of data elements including, but not limited to, one or more equipment types and a respective cost associated therewith. Algorithm 10 receives each of inputs 20-22 and determines an optimized network configuration dependent upon wavelength groupings, available equipment, acceptable signal loss, QoS specifications, and/or other network design characteristics as described herein. Optimization is performed by algorithm 10 by minimizing the number of wavelengths supported by the network, evaluation of various clear and unclear light path options and resulting optimization selection between equipment costs and unnecessary OEO regeneration, optimized network configurations resulting in selection between OEO and OLA costs, and/or network configuration optimization based on modeled optical signal characteristics and corresponding reconfiguration of network infrastructures. Moreover, algorithm 10 is constrained by performance attributes for each type of available equipment, acceptable wavelength routing with minimized wavelength conversion, and/or optimized wavelength grouping and sequencing. Algorithm 10 receives and processes inputs 20-22 and provides one or more outputs such as an optimized network map output 30, a network layer output 31 and a site output 32. Network layer output 31 may comprise data elements defining a routing and wavelength assignment (RWA) for each traffic demand and associated QoS provided in an input to algorithm 10. As used herein, RWA refers to a particular route of a network on which a traffic demand is conveyed from a source site of the network to a destination site of the network and includes an identification of the wavelength(s) of which the traffic demand is conveyed along the assigned route. A route, as used herein, refers to a path by which a traffic demand may be conveyed through the physical layer of a network from a source site to a destination site and preferably includes each link, that is fiber, the origination site, destination site, and any intermediate sites therebetween through which the traffic demand is conveyed. A link budget may also be provided for all optimized light paths. Site output 32 may comprise an equipment listing for each site of the network design as well as associated costs of the equipment entities selected for each site. Additionally, add/drop group sequencing may be specified for each site of the network design. [0033] Traffic input 20 preferably specifies parameters defining a bandwidth, protocol, and QoS requirements for a desired service between various site locations of the network design. Parameters of traffic input 20 may be provided to a network designer by a subscriber and may reflect data transfer rates, protocol requirements, and or other traffic demands between two or more sites. Traffic input 20 may be maintained in a text file, or other suitably formatted data structure, and read by algorithm 10. With reference now to FIG. 2A, there is a simplified traffic demand schematic (as defined by traffic input 20) for which a network design may be generated by algorithm 10. In the exemplary network traffic demand schematic, various data traffic demands are defined between seven network sites 110-116. Each traffic demand defined between two sites includes a bandwidth requirement. In the illustrative example, a solid line interconnecting two sites indicates a Gigabit Ethernet (GE) traffic demand and a dashed line illustratively denotes an OC-48 transport service bandwidth requirement. Table A summarizes exemplary traffic demand requirements among nodes 110-116 that may be provided to algorithm 10 via traffic input 20. [0034] As shown, traffic input 20 defines traffic demands between various sites and specifies a required bandwidth for each traffic demand, as well as a quantity specification, and a path diversity. Path diversity specifies whether the link is unprotected or protected, that is whether routes may travel over a common physical connection, i.e. fiber, or whether two routes may not share any common physical connections. For example, two traffic demands (traffic demand 1 and traffic demand 2) are defined for transfers between sites 110 and 111. Traffic demand 2 is required to have GE bandwidth capacity and is denoted to have a quantity �2� and a path diversity value of �1+1�. In the illustrative example, a diversity value of �None� denotes an unprotected route while a diversity value of �1+1� denotes a protected route featuring redundancy on both a line side and transmission side, that is redundancy of access cards for interfacing with a subscriber tributary and redundancy of light path (i.e. redundant fibers). Thus, traffic demand 2 requires two different routes, as denoted by the quantity value of �2�, and the traffic for which the two routes are to be provisioned may not travel over the same physical link, as denoted by the diversity value of �1+1�. On the other hand, traffic demand 3 defined for a data transfer requirement between sites 110 and 114 requires four separate routes for data transfers but all traffic may be conveyed over a common physical link, as denoted by the diversity value of �None�. Other redundancy configurations are possible. For example, light path redundancy may be provided by having redundant transmission cards while no redundancy of access cards is provided. Such a redundancy configuration may be denoted by a diversity value of �L1+1� that indicates a configuration featuring a light path diversity. [0035] Bandwidth requirements are defined in traffic input 20 by specifying one of various fiber availabilities. For example, traffic demand 1 is specified to have a bandwidth requirement of OC48. However, the bandwidth requirements of an interconnection may be specified in other formats such as a bit rate or another numerical metric. Common fiber availabilities and associated bit rates that may be used to specify a required bandwidth of a traffic demand are summarized in TABLE B. [0036] With reference now to FIG. 2B, there is a simplified schematic of a physical layer 140 of a network design that may be generated by algorithm 10 and that has sufficient capacity to deliver the traffic demands defined by traffic input 20. Physical layer 140 comprises site 110-116 to which traffic demands are defined and physical links 130-136 respectively interconnecting two of sites 10-116. Each link 130-136 generally comprises one or more bi-directional optical fiber pairs. The number of fiber pairs in a particular link 130-136 is dependent upon the traffic demands that may be routed therethrough and is optimized by algorithm 10 in a manner such that the total number of fiber pairs is minimized without adversely effecting the network design, that is without undesirable impacting the network design performance and/or cost. In other words, the number of fiber pairs is one exemplary network parameter that may be manipulated during network design such that the final selection of fiber pairs provides an optimized network infrastructure having the least overall cost while still allowing the network design to meet the traffic demand requirements. Each of sites 110-116 is �populated� (or assigned) with optical network components, such as multiplexers/demultiplexers, amplifiers, etc., by algorithm 10 in a manner such that sites 110-116 have sufficient capabilities to satisfy the network requirements defined by traffic input 20 according to an embodiment of the present invention and as described more fully hereinbelow. [0037] Attribute input 21 provides physical attributes of sites of physical layer 140 and requisite fiber optic link characteristics between sites 110-116. Attribute input 21 may include geographical coordinates, such as a longitude and latitude, for each site location, fiber length, fiber count, and facility size. TABLE C summarizes exemplary site 110-116 information that may be provided by attribute input 21. [0038] As summarized by TABLE C, the connectivity defined by attribute input 21 may additionally provide a name for each physical link between two sites, a resource type of the link, such as True Wave, a fiber count of the link, the sites that terminate the link and thereby define the connectivity of the link, the fiber distance of the link, as well as other attributes of the physical layer 140. [0039] Each of links 130-136 are respectively terminated by two sites 110-116 and may be referred to as point-to-point links. A typical point-to-point optical link comprises a transmitter (laser), transmission medium (optical fiber), one or more multiplexer/demultiplexers (OMXs) and a receiver (detector). Metropolitan networks have different requirements compared to long haul networks because the distance between nodes are shorter and therefore signal loss may be dominated by OMX losses. Frequent bandwidth grooming, that is the assignment of a traffic demand (or a portion thereof) to a particular bandwidth, and sophisticated link management are required to handle the traffic. Light path design is carried out using individual wavelength power budgets. In optical power budgeting, the optical power is calculated for the total link including the loss at different places along the link and at all systems involved in provisioning of the link. This optical power budgeting is computed for every service channel. Significant losses introduced by network components, or infrastructure, include fiber transmission losses (dB/km), connector losses (dB/con.), splice losses (dB/splice), losses introduced by intermediate link systems, such as an OMX, a power margin for future services, as well as other losses. A requisite optical power at a receiver for a particular link may be estimated by:
[0061] where ΣFibers is the link loss in the fiber path. The minimum signal loss model may easily be modified to compensate for new optical components and/or new equipment vendors. [0062] It should be understood that equation 4 is only an exemplary technique for modeling signal losses and other techniques may be employed by the invention. For example, in a preferred embodiment of the present invention attenuation losses imparted on an optical signal as it is passed through various components of the network design are modeled according to performance characteristics of the modeled component. Additionally, dispersion losses, for example polarization mode dispersion and chromatic dispersion, such as channel effects on individual light paths are modeled. It should be understood that any network component may effect the optical signal quality and may be modeled accordingly. Pursuant to providing a network design featuring the most economical infrastructure available, other network characteristics may be modeled and considered during network design. For example, component life expectancies may be modeled and estimated replacement costs may be considered when generating a network design. [0063] For ring and mesh based networks featuring route protection, the network designer must allocate lambdas in multi-directional routes to deliver availability requirements by service providers. Prior to assignment of wavelengths, the shortest signal-loss routes available to deliver traffic from the source(s) to the desired destination(s) are computed to facilitate simplification of various subroutines of algorithm 10. Additionally, algorithm 10 may compute path reliability based on the reliability of individual components that the light signal passes through. Assignment of lambdas based on potential routes is described more fully hereinbelow. [0064] Physical links interconnecting different sites may share one or more lambdas, that is a particular optical wavelength may be commonly transmitted over physical links interconnecting different sets of sites by a technique commonly referred to as wavelength reuse. Shared lambda routes are composed of several point-to-point routes that form a system ring. The shared wavelength routes may be found by decomposing the ring into individual point-to-point traffic that can be evaluated using Dijkstra's algorithm or another suitable algorithm. [0065] Routing and wavelength assignments (RWA) and waveband grouping of lambda-level traffic may be performed after identification of potential fiber routes (step 420). The well-known Greedy algorithm, or another similar application, is invoked to determine an optimized traffic wavelength and routing assignments. Traffic may be assigned in descending order of total bandwidth consumed and traffic parameters used for evaluation of RWA and waveband grouping preferably include traffic demand and signal route loss. Parameters involved in RWA and waveband grouping may be weighted such that one parameter, for example a traffic demand parameter, has greater influence over another parameter in determination of appropriate RWA and waveband groups. For each traffic demand, several RWA computations are preferably made. A clear path is first considered for each wavelength assignment to facilitate minimization of OEO. If a clear path is unavailable, an unclear path is thereafter considered and a minimum converter algorithm is invoked to determine an optimized unclear path. Unassigned traffic will then be input in an unassigned queue. If the unassigned queue does not have capacity for any unassigned traffic, additional fiber and/or additional wavelength(s) will be required to support the network traffic demand. [0066] RWAs are first attempted to be made on clear, that is continuous, path routes. If a clear path is unavailable, algorithm 10 then attempts to determine a suitable unclear path for the traffic. If both a clear path and unclear path are unable to be determined for a traffic demand, or a portion thereof, the well-known Ford-Fulkerson's method of maximum flow is invoked to assign wavelengths to the traffic without increasing the capacity of the network. Accordingly, OEO transponders are required. As mentioned hereinabove, an unclear path assignment comprises a path where a unique wavelength is not available on all the links throughout the path for delivery of a traffic load from the source to destination site. Therefore, different segments of the route will have different wavelengths assigned thereto and wavelength conversion is thus required. Algorithm 10 attempts to minimize wavelength conversions by selecting an available wavelength that traverses more links along the path than other available wavelengths. This process is iteratively repeated along all route segments until the destination node is reached and, accordingly, the complete route involves the minimum OEO conversions available. [0067] A wavelength matrix may be defined that is accessible by algorithm 10 for facilitating allocation of lambdas. An exemplary wavelength matrix accessible by algorithm 10 is three-dimensional and may be represented as: [0068] where: [0069] Λi,j,k=
[0070] 1, if allocated [0071] 0, unallocated [0072] i=wavelength; [0073] j=identification of the traffic source; and [0074] k=destination site for a particular traffic load. [0075] The wavelength matrix is used to record global resource allocations for the wavelength assignments within the network. The wavelength matrix shown in equation 5 provides only a portion of a full wavelength matrix for simplification of description and due to symmetry of the wavelength matrix. [0076] Inefficient waveband grouping may result in an undesirable increase of the total cost of infrastructure for a network design due to an increase in resource requirements, such as shelves, lasers and detectors. Algorithm 10 correlates wavelength add and drop procedures to wavelength banding to potentially reduce the requisite number of network equipment entities. A two-dimensional array may be defined that records the total number of times a potential lambda is dropped (or added) along with another lambda. [0077] Algorithm 10 evaluates waveband grouping on a site-by-site basis. The procedure used by algorithm 10 for evaluating potential waveband groupings may better be understood with reference to the site schematic of FIG. 8A that shows a network site 600 terminating three incoming links 610-612 (fibers). In the illustrative example, link 610 is dropping wavelengths λ1, λ2, and λ5, link 611 is dropping wavelengths λ5 and λ6, and link 612 is dropping wavelengths λ2, λ3, and λ4. An array 620 for recording the count of add/drops of each lambda with another particular lambda has N-rows and columns, where N is the total number of lambdas in the current network design, as shown in FIG. 8B. A partial array 620 for a network including the exemplary node 600 will include six rows and six columns with scalar entries Xi,j, as well as rows and columns for any other wavelengths not terminated at the particular site shown in FIG. 8A. Each wavelength pair combination added or dropped at a common link has a corresponding entry in the array incremented. In the present example, wavelength pairs λ1 and λ2, λ1 and λ5, and λ2 and λ5 commonly dropped from link 610 have corresponding entries X1,2, X1,5 and X2,5 of the array incremented. Likewise, wavelength pairs λ5 and λ6 commonly dropped from link 611 have entry X5,6 incremented and wavelength pairs λ2 and λ3, λ2 and λ4, and λ3 and λ4 commonly dropped from link 612 have corresponding entries X2,3, X2,4 and X3,4 incremented. Algorithm 10 may then evaluate matrix 620 at each link and selection of wavelengths to be added or dropped may be facilitated by the add/drop counts maintained by array 620. Higher correlated wavelengths, that is wavelengths more often determined to be added and/or dropped together, are accordingly placed in a common band. Upon completion of waveband grouping, algorithm 10 may then generate more detailed network infrastructure information. [0078] Returning again to FIG. 6, each site of the network design may now be populated with equipment, that is algorithm 10 may now consider the impact of various equipment types and vendors, that is various component models of equipment classes, on the overall performance and cost of the network design according to an automatic equipment engineering subroutine of algorithm 10 (step 425). The automatic equipment engineering subroutine includes an iterative process of populating each site of the network design with network components and analyzing optical characteristics of the resulting network configuration by a technique of calculating signal traces. As used herein, signal trace refers to a modeled optical signal having calculated attributes representative of various optical signal metrics, such as attenuation, noise, jitter, and/or other losses incurred during conveyance through a network and the various constituent components thereof. A calculated signal trace may include various attributes including power level, OSNR, chromatic dispersion level, polarization mode dispersion level, and/or crosstalk level as well as other signal attributes that each may be calculated at discrete positions within a network configuration along a defined optical light path, such as at the input and/or output of various network components positioned in the light path. As used herein, a light path is associated with a route and, in addition to identification of the source site, destination site, any intermediate site(s), and the fiber(s) through which the traffic demand is conveyed along the associated route, includes each individual network component through which the traffic demand passes (or is otherwise processed) during traversal of the traffic demand through the associated route. Thus, the signal trace is a logical representation of an optical signal and facilitates network design analysis of optical path characteristics, for example jitter, attenuation, dispersion, and/or other signal losses or distortion, that may be imparted on a signal as it is propagated through a network along a route from a source site to a destination site and through various network components therebetween. Each network component, for example fiber, amplifiers, multiplexers, splitters, etc., may effect one or more signal characteristics. The present invention generates a signal trace that preferably includes estimated signal mean and variances of an optical signal transmitted through the various network components. The impact of the signal losses on the overall network design is then analyzed (via analysis of the signal traces) prior to selection of a final configuration of the network design. Moreover, generation of signal traces for all required light paths facilitates an optimized and automated selection of amplifier and/or regeneration stage placement within the network design according to an embodiment of the present invention and as described more fully hereinbelow. The equipment population on each site will be based upon equipment constraints that may be taken from equipment vendor publications, laboratory analysis of equipment, and/or other information sources that provide operational characteristics of network components that may be included in the network design. Prior to this stage, only an approximation of signal loss is used to evaluate traffic routes based on approximations of equipment deployment. [0079] The requisite equipment at a particular site is dependent on the traffic flow at the site. A traffic flow data structure is used to maintain a record of traffic flow(s) at each site of the network design. The traffic flow data structure may maintain individual traffic flows at each fiber of a site by a link-list or other suitable data structure. The traffic flow data structure specifies the source wavelength and fiber and the destination wavelength and fiber for each lambda-level traffic demand. In FIGS. 9A-9D, there is a simplified block diagram of four different traffic types that may be maintained by the traffic flow data structure for a site 701 of a network. Site 701 is interconnected by fiber links 710-711 with respective network sites 700 and 702. In FIGS. 9A-9D, traffic flows 715A-715D may originate, pass-through, or terminate at site 701. In FIG. 9A, site 701 is a traffic source and originates data traffic 715A that is directed to site 702 via link 711. In FIG. 9B, site 701 is a destination site and receives data traffic from site 700 via link 710. In FIG. 9C, site 701 is a pass-through site and conveys data traffic 715C received from site 700 via link 710 and passes the traffic 715C to site 702 via link 711. In FIG. 9D, site 701 conveys data traffic from site 700 to site 702 via links 710 and 711 and functions as a conversion node in which traffic 715D received from site 700 is subjected to wavelength conversion and thereafter passed to site 702 via link 711. Traffic originating from a source site and transferred to a destination site via an intermediate site therebetween is classified as pass-through traffic if the carrier wavelength is identical on both links. For example, traffic 715C is classified as pass-through traffic if wavelengths allocated on links 710 and 711 for passing traffic 715C are identical. Traffic originating from a source site and transferred to a destination site via an intermediate site is classified as wavelength converted traffic if the carrier wavelength of the traffic entering the intermediate site differs from the carrier wavelength exiting the intermediate site. For example, traffic 715D may be conveyed from site 700 to site 701 via link 710 on a first wavelength λ1. Site 701 may then convert the traffic to a second wavelength λ2 and transmit the traffic via λ2 to site 702 over link 711. In such a scenario, traffic 715D is said to be wavelength converted and site 701 must have a wavelength converter therein to perform the channel conversion for passing traffic 715D from site 700 to site 702. Accordingly, algorithm 10 classifies inbound and outbound traffic at each site as source traffic, destination traffic, pass-through traffic, or conversion traffic. [0080] Thereafter, automated equipment engineering is performed by algorithm 10 for the sites of the network design and an optical path analysis is performed to determine signal trace characteristics and amplification and/or regeneration stage placement as described more fully hereinbelow. For each source and destination site of the network design, transmission laser(s) and detector(s) are allocated to meet the add/drop traffic requirements. Thereafter, wave-band grouping is considered and may effect common equipment selection. A site information data structure contains logical association(s) with an equipment information data structure. Particular equipment entities may be constrained to have limited directionality, for example a laser transmitter may only be operational on outbound links from a network site. FIG. 10A is a block diagram of the logical relationship between a site information data structure 750 and one or more equipment data structures 760A-760N. Each site of the network design has a respective site information data structure 750 associated therewith. Each equipment shelf of each site, in turn, has a respective shelf entry 760A-760N in the equipment data structure that has a respective logical association 755 and 756 with site information data structure 750. FIG. 10B is a simplified block diagram of a shelf 780 that may comprise two banks 785 and 786 of directional transponders 785A-785F and 786A-786F and that may be logically represented by shelf data structure 760A. Each of transponders 785A-785F and 786A-786F may be responsible for generating a particular waveband. Generally, a waveband is associated with a direction (from one origination site to a destination site) and, accordingly, each transponder 785A-786F may be responsible for optic modulation of a waveband from one site to another. Accordingly, transponders 785A-786F are considered directional equipment. [0081] Wave-band grouping of pass-through traffic at a site may be performed under one of two general scenarios: the waveband a wavelength belongs to is not an add/drop wavelength at the site or the wavelength belongs to a waveband that is add/dropped at the site. In the former case, no additional DWDM line card equipment is required, that is, no optical conditioning of the waveband is required to be performed by the site and the traffic is passed through the site as received. Accordingly, in such a scenario, no equipment population is needed for pass-through of the waveband. In the latter case, the waveband that the wavelength belongs to is added (or dropped) at the site of the network design. If the pass-through traffic is on a wavelength being dropped, the pass-through traffic is regenerated prior to being retransmitted from the site and two DWDM transmission transponders are required. One transmission transponder is needed to support wavelength conversion and an additional line card transponder is required to transmit the traffic to the destination subscriber tributary for the wavelength(s) carrying subscriber traffic that is dropped. Algorithm 10 optimizes wave-band grouping to minimize OEO equipment as discussed hereinabove. In this phase, all pass-through channels will be evaluated if the band is added or dropped at the site. Additional equipment will be populated if OEO is required. [0082] A centralized equipment count for the network design is provided through the use of an equipment matrix E. The exemplary equipment matrix has a row dedicated to each site of the network design and each column thereof is assigned to resources of a site. Thus, a particular equipment entity may be indexed by indexing the row number that corresponds to the site and the column number that is associated with the particular site equipment. Additionally, each site has a list of shelves allocated to it. Traversal through the equipment matrix may be made such that each shelf of any network design site may be indexed and incremented as shelves are added to the network design. Each equipment matrix entry may maintain a count of transponders at each site as well and, accordingly, as transponders are added, the transponder count of a shelf may be incremented to indicate the overall shelf and transponder count of each site of the network design. [0083] Thus, the equipment matrix represents the number of components located throughout the network, where R represents the total number of components and the column index n represents the site index. [0084] With reference again to FIG. 6, a cost evaluation of the network design configuration is next made (step 431). A cost evaluation will be made for the equipment required in all sites within the network design. Preferably, the cost evaluation is based on transmission costs within the network. A unit price matrix U is generated and represents the individual unit price cost for different components of the network design as defined by equation 6.
[0087] where i is an index to a particular site of the network design. Thus, the site cost matrix is a 1�N matrix where N is the total number of network design sites. The site cost matrix may be generated by multiplying the unit price matrix by the equipment matrix. Thus, a total equipment cost, C, may be computed by summing the individual entries of the site cost matrix. [0088] As described, algorithm 10 generates a cost evaluation for the network design developed to satisfy a customer traffic requirement. An optical path analysis is then preferably performed as part of the automatic equipment engineering routine by calculating signal traces, or optical signal models, according to an embodiment of the invention and the steps of equipment provisioning and optical path analysis may be iteratively repeated until an optimized network design configuration providing the most beneficial light path characteristics is determined. [0089] Performance characteristics of all available network components may be modeled and their respective impact on the overall network design performance and cost may be accounted for in the network design process by calculating each component's contribution to signal loss. Table D summarizes exemplary laser transmitter and detector characteristics that may be modeled on an individual component basis and used by algorithm 10 for calculating signal trace attributes, network infrastructure costs, and/or other parameters effecting the network design. [0090] Each of the transmitter and receiver parameters summarized in TABLE D have exemplary parameter values assigned thereto that are device dependent, that is a plurality of transmitter and/or detectors may be available for placement in a design network and, preferably, each available transmitter and detector would have performance parameters individually defined therefor. Performance parameters of an individual component may be obtained from vendor specifications, testing, or other information sources. [0091] As an optical signal is propagated through a fiber and subjected to optical conditioning, such as OEO regeneration, a variance, such as signal jitter, is imparted on the signal. The amount of jitter imparted on the optical signal may be a function of the number of regenerations to which the optical signal is subjected. Modeling of signal jitter may be a simple function of the quantity of the number of regeneration procedures and the amount of jitter introduced by each regeneration component. A discrete jitter power penalty may accordingly be introduced into a signal trace calculation by deducting a calculated decibel value from the signal trace power level at discrete locations within the network design. For example, a count of regeneration stages between a site from which the signal trace exits and another site subsequently entered by the signal trace be made and a jitter power penalty may be deducted from the calculated power level at the entry site prior to calculation of the signal trace power level, OSNR, or other characteristic, at any component locations within the site. [0092] The bit error rate at a receiver is generally a result of the optical signal to noise ratio. Propagation of the optical signal through the fiber may contribute to the OSNR. Preferably, the OSNR contribution is modeled for any network component that contributes noise to the optical signal and is included in a signal trace model developed by algorithm 10 An OSNR penalty is then computed on a per component basis and introduced into the signal trace upon calculation of the signal trace at the respective component location. [0093] Polarization mode dispersion of an optical signal is caused by non-symmetries in wave guides and is accumulated as the optical signal is propagated through the physical link and contributes to the overall distortion of the optical signal. Preferably, polarization mode penalties are applied at the receiver based on an estimated polarization accumulated during the modeled signal propagation through the link and may be subtracted from the signal trace power level at entry to a receiver. Thus, a PMD penalty may be introduced into the signal trace and may be function of a discrete fiber characteristic and a length of the fiber designated for implementation within the network design. [0094] Optical signals are susceptible to chromatic dispersion, in addition to PMD, as a result of the particular fiber type utilized in a physical link and the length of the fiber. Accordingly, chromatic dispersion may be included within a signal trace and a chromatic dispersion power penalty may be levied at each receiver of the signal trace. [0095] Coherent cross talk may be introduced into an optical signal at a multiplexer during performance of a drop procedure. A cross talk ratio may be estimated by computing a desired power of an optical signal exiting a network design site divided by a leakage signal from the dropped signal. The isolation loss combined with the band pass loss is used to compute the leak signal power at the interference point. [0096] Signal filtering performed by OMXs during add and/or drop procedures may introduce various signal losses and may impart such losses on signal bands and to individually added and/or dropped wavelengths and may be included within a signal trace by introduction of an appropriate penalty. TABLE E summarizes various filter parameters that may be modeled and the effect thereof may be included in the calculation of one or more signal trace attributes. Particular values assigned to a filter parameter are filter dependent. [0097] Couplers and splitters may contribute to signal attenuation, PMD, and/or other signal degradations. TABLE F summarizes exemplary coupler and splitter parameters that may be included in calculation of a signal trace. The particular value assigned to a coupler or splitter is device dependent. [0098] Optical amplifiers may introduce noise, PMD, and/or other losses to an optical signal during amplification of the signal that may be modeled by a signal trace. Additionally, each available amplifier will have defined performance limits and/or tolerances, such as an operational bandwidth, a minimum and maximum signal input power, as well as other performance parameters. TABLE G summarize exemplary amplifier performance parameters that may be modeled by algorithm 10 and included within a calculated signal trace on a device-dependent basis. [0099] A better understanding of light path analysis and equipment provisioning of the network design as performed by an embodiment of the present invention may be had with reference to the equipment provisioning flowchart of FIG. 11 that shows, in part, a simplified processing of the automatic equipment engineering routine (step 425 of FIG. 6). As described hereinabove, traffic at each site is classified as origination, pass-through, wave-converted or destination and, accordingly, the requisite equipment at the particular site for processing the traffic may be defined by the traffic classification. [0100] Equipment provisioning commences by reading a traffic flowi classification (step 430A) and determining whether the traffic flowi is classified as origination traffic (step 430B). An affirmative evaluation thereof results in population of site equipment requisite for processing origination traffic (step 430C). Algorithm 10 processing may then evaluate whether additional traffic flows remain for additional equipment population (step 430D). A determination of additional traffic flows may result in incrementing a counter i (step 430E), or performing another process that facilitates reading of the additional traffic flow classification, and returning algorithm 10 processing to step 430A. If traffic flowi however, is not determined to be classified as origination traffic, algorithm 10 may next evaluate traffic flowi to determine if the traffic flow is classified as destination traffic (step 430D). An affirmative evaluation of traffic flowi as destination traffic results in equipment population of the site for performing a drop (step 430F) procedure and processing may proceed to evaluation of additional traffic flows (step 430D). Failure to identify traffic flowi as either an origination or destination traffic flow results in next evaluating the traffic load as pass-through classified traffic (step 430H). Confirmation of classification of traffic flowi as pass-through traffic results in requisite equipment population of a laser transmitter, a detector, and/or equipment for performing add/drop procedures of the traffic flow, as need be (step 4301) for populating the site such that it is operable as a pass-through site and thereafter algorithm 10 may proceed to evaluate whether additional traffic flows exist for the site (step 430D). Failure to identify the traffic flowi as pass-through traffic results in the identification of the traffic as wavelength converted traffic and, accordingly, site equipment is populated therefor (step 430J). Thereafter, algorithm 10 may proceed to evaluate whether additional traffic flows exist for the site (step 430D). Upon equipment population for all traffic flows at all network design sites, algorithm 10 may proceed to perform an automated link engineering routine (also referred to as an optical path analysis) (step 430K) and subsequently output an equipment list for the site of all equipment components added during each iteration of the processing flow described (step 430L). [0101] The automatic link engineering procedure involves modeling light path characteristics, that is generating signal traces, of the network design and automatically disposing network components, such as optical amplifiers, regeneration components, or other devices, within the network design to compensate for optical signal deterioration according to an embodiment of the invention. Pursuant to reducing the overall network design cost, the automatic link engineering procedure utilizes a cost analysis to select the most economical network solution that satisfies the network performance requirement, that is the overall subscriber traffic and performance demands. As components are added and/or removed from the network design, all of the network design wavelengths must be re-evaluated for network propagation and deterioration characteristics to ensure appropriate signal levels are present at all network receivers. [0102] With reference now to FIG. 12, there is shown a flow chart depicting the automatic link engineering procedure (step 430K) of FIG. 11. The automatic link engineering procedure is initiated by reading the equipment population of each network design site by an automatic dispersion compensation routine (step 430P) that may compensate for dispersion losses by designating placement of one or more regeneration and/or dispersion compensation modules within the network design. Thereafter, automated placement of amplification and/or regeneration stages may be performed by sequentially developing signal traces and determining locations within the network having unsuitable signal attenuation and/or distortion (step 430Q). Each regeneration stage may then be evaluated for necessity of inclusion within the network design by sequentially designating each regeneration stage for removal from the network design, recalculating signal traces, and analyzing resulting signal trace attributes (such as PMD, chromatic dispersion, jitter, or other calculated distortion attributes) for evaluation of unacceptable distortion (step 430R). Likewise, amplification stages may be sequentially designated for removal and modeled signal levels may be recalculated and analyzed to determine whether any signal levels have unacceptable attenuation as a result of removal of a the amplification stages (step 430S). Additionally, optimization of optical attenuation may be performed to ensure that optical signal power levels at any amplification stage inputs do not exceed the input power ratings of the amplification stages (step 430T). [0103] With reference now to step 430K of FIG. 12, the automatic dispersion compensation routine models the accumulation of polarization mode dispersion and chromatic dispersion due to channel effects along individual light paths. An analysis of the modeled dispersion level against a maximum allowed dispersion level is made. If a signal trace is determined to have a dispersion level in excess of a maximum dispersion allowed, a regeneration stage and/or a dispersion compensation module may be selected for placement within the network design. As is known in the art, a regeneration component may comprise an OEO component that performs optical-to-electrical-to-optical signal conversion such that the signal, when converted to the electrical state, may be retimed, reshaped, and reamplified so that the signal, when converted back to the optical state, is suitably conditioned for conveyance in the network. A regeneration stage comprised of a dispersion compensation module, on the other hand, performs optical conditioning entirely in the optical domain. Selection of an OEO regeneration component may be made between a normal or extended regeneration transponder. In some network scenarios, dispersion compensation modules may not be a practical solution for optical signal conditioning and only regeneration stages may be selected for remedying unacceptable signal dispersion. The automatic link engineering algorithm calculates a cost of different dispersion compensation systems and automatically selects the components(s) that suitably compensate for the dispersion effects at the most economical cost. In addition to dispersion losses accumulated on the optical links, signal and OSNR losses are also modeled as the wavelength passes through filters, links, couplers, splitters, and connectors. The automatic link engineering procedure models these losses to determine their effect on requisite signal amplification and electrical regeneration as described more fully hereinbelow with reference to FIG. 14. [0104] In the event a dispersion compensation module may not be implemented within the network design, a process for selection between a normal transponder and an extended transponder may be performed as described with reference to FIG. 13 that shows a flowchart for an automatic dispersion compensation routine performed in accordance with step 430P of FIG. 12. The dispersion compensation routine is initiated by retrieving a dispersion limit for a normal transponder (step 431A). Thereafter, the number of retime/reshape/reamplify procedures required to compensate for signal dispersion is calculated based on the normal transponder performance characteristics and the resulting signal trace dispersion level (step 431B) and a cost of dispersion compensation is thereafter calculated (step 431C). An evaluation of whether an extended transponder may be disposed within the network where dispersion compensation is required is next made (step 431D). If placement of an extended transponder is not available, the normal transponder is selected and disposed within the network design (step 431E). If, however, an extended transponder may be disposed within the network design, retrieval of the dispersion limit of the available extended transponder is made (step 431F) and the number of retime/reamplify/reshape procedures is determined (step 431G). Thereafter, a cost of dispersion compensation utilizing the extended transponder is made (step 431H) and a comparison is made with the cost determined for implementation of a normal transponder (step 431I). Placement of the extended transponder within the network design is made if it is determined that signal compensation using the extended transponder is more economical than using normal transponders (step 431G). Otherwise, the normal transponder is selected for placement in the network design (step 431E). [0105] A signal originating from a site is generated from a transmitter disposed within the site and has a particular power level provided to the signal dependent on the output power of the laser transmitter. The signal may pass through any number of sites, components in the various sites, and fiber(s) interconnecting any sites between the origination and destination site as the signal is conveyed through the network towards a destination site. The signal may be attenuated during the conveyance process by any of the components and/or fibers through which it passes. For example, the signal may be passed through a splitter at a site that has to drop another wavelength in a common band with the signal. Often times, a signal will pass through an amplification stage in series with a splitter. Both the amplification component and the splitter component can attenuate the signal, as well other components through which the signal passes, such as combiners, physical links, etc. If the attenuation imparted on the signal is sufficient to drop the power level of the signal below the sensitivity of the receiver at the destination site or any intermediate site(s), an amplification stage must be disposed within the network. The present invention models attenuation characteristics of each network component that may be included in the network design and thereby generates signal traces that have calculated attributes representative of a signal loss of a respective signal throughout its light path from an origination to a destination site. Accordingly, stages requiring signal amplification may be determined by algorithm 10. If it is determined that a signal attenuation is sufficient to decrease the power of a signal below the sensitivity of a receiver within the light path of the signal, an amplification stage is designated to be positioned at an exit of the last site where the signal power is sufficient for accurate reading of the signal. For example, if a signal that is generated at an origination site passes through an intermediate site prior to reaching a destination site, a signal trace may be generated that approximates the attenuation of the signal as it leaves the origination site, transfers over the link interconnecting the origination and the intermediate site, and includes any attenuation imparted on the signal while passing through the intermediate site and the final link interconnecting the intermediate site with the destination site. At any point along the light path that attenuation is sufficient to reduce the signal power below a sensitivity of a receiver at any site within the light path, an amplification stage is designated to be placed at the exit of the previous site. For example, if the signal trace indicates that the signal is sufficiently powered to be suitably read by a receiver at the intermediate site but insufficient to be read by the receiver at the destination site, an amplification stage is designated to be positioned at the exit of the intermediate stage in order to provide sufficient power for the signal to be read by the receiver at the destination site. This process is repeated for each required signal along the associated light path of the signal in the network design. Designation of placement of an amplification stage is herein referred to as amplification �voting� and defines an amplification stage location, such as a site, and may include a directional designation (such as �entry� or �exit�) of the amplification vote. [0106] In addition to attenuation of the optical signal, a noise attribute such as an OSNR, as well as other distortion attributes, e.g. jitter, PMD, chromatic dispersion, etc., may be introduced by various network components and may be modeled as described hereinabove. Each receiver has an OSNR limit that, if not met by the optical signal, may result in an inaccurate or missed reading by the receiver. Similar to tracing of the attenuation of a modeled signal along a light path, OSNR and other signal trace attributes representative of various signal distortions may be traced as well. If a calculated OSNR is greater than a minimum OSNR limit at a detector, a vote for an electrical regeneration stage is placed at the previous site that may have a regeneration stage placed therein. Thereafter, the voting process is reinitialized and reexecuted. [0107] Evaluation of an unacceptable signal distortion attribute or power level may be made at a site entry and/or a site exit depending on the traffic scenario being evaluated. For example, if it is determined that a signal trace has a sufficient power level at an input of a particular site, the signal trace may then be calculated through additional components at the site, such as filters or other components. The signal may be subjected to regeneration at the site and, accordingly, a receive sensitivity thereof may be evaluated. A signal trace determined to have an insufficient signal power level will result in a vote for an amplifier stage at the current site and, accordingly, an amplification stage vote is designated for the site. Likewise, power levels of the signal trace may be evaluated at a site exit and votes may be cast for a site on either (or both) a site entry or site exit. Each wavelength is limited to a maximum of one vote per direction. If multiple votes are cast for an amplification stage and/or a regeneration stage, an amplification and/or regeneration stage vote is placed at the first location receiving the vote during signal trace calculation. Signal traces are then recalculated and this procedure continues until no additional votes are placed for amplifiers and/or regeneration stages. [0108] In FIG. 14, there is shown a flowchart depicting a subroutine performed by the automatic link engineering routine according to a technique that facilities automated placement of amplification and/or regeneration stages within the network design in accordance with step 430Q of FIG. 12. Prior to execution of the amplification/regeneration site selection routine, all possible light paths through which a signal trace may be calculated are defined within a temporary array, or another data structure. Preferably, each light path definition includes network component identifiers included within the light path definition, or another logical link thereto, such that a particular light path may be indexed and corresponding component performance parameters of network components included within the light path of the signal trace may be conveyed to the amplification/regeneration subroutine for calculation of a signal trace. An index may first be initialized (step 432A) and calculation of a signal tracei is then performed (step 432B). Evaluation of the signal tracei is then made to determine if the current network design configuration requires addition of any amplification and/or regeneration stage(s) (step 342C). Evaluation of a required amplification stage may be made, for example, by comparing the signal power input requirement of each component included within the light path of the calculated signal traces with the calculated signal trace power level at the input of the respective network component. Similarly, evaluation of a requirement for a regeneration stage may be made, for example, by comparing an OSNR input threshold (and/or another input signal distortion limit) of each component included within the light path of the calculated signal trace with the calculated signal trace OSNR (or another distortion attribute) at the input of the network component. If amplification and/or regeneration stage(s) are required, amplification and/or regeneration stage(s) are accordingly designated at a determined position(s) within the network design where placement of such a stage would compensate for unacceptable signal attenuation and/or distortion by placing an amplifier and/or regeneration vote at the determined position (step 432D). For example, if a signal tracei power level is calculated to be below an input requirement of an OMX 163 of a transit site 160 included in the light path of the signal traces, an amplification vote may be designated at the input of transit site 160. Similarly, if an OSNR of a signal trace is calculated to be insufficient for the input of an FPP 181 of a destination site 180, a regeneration component may be designated for placement at the exit of the previous site in the light path of the calculated signal tracei by placing a regeneration vote at the exit of the previous site within the light path. It should be understood that amplification and regeneration stage �voting� is a technique for accumulating a count of required amplification and regeneration stages (and a corresponding location thereof) within the current network design and recordation of amplification and regeneration votes may be made in an array or another suitable data structure. Upon designation of placement of one or more amplification and/or regeneration stages within the network design, the signal trace index is re-initialized (step 432E) and processing is returned to calculating of signal tracei. Reinitialization of looping through the amplification and regeneration placement subroutine is performed as a consequence that placement of an amplification or regeneration stage may effect previously considered signal traces. Signal traces calculated subsequent to designation of placement of an amplification and/or regeneration stage at step 432D are made with the amplification and/or regeneration stage designated for inclusion within the network design. That is, a signal trace calculated after voting for an amplification and/or regeneration stage will include the effects of the designated amplification and/or regeneration stage if the designated amplification and/or regeneration stage is within the light path of the subsequently calculated signal trace. An evaluation that no amplification or regeneration stages are required for the signal tracei results in incrementing of the signal trace index (step 432F) and subsequent evaluation of whether additional signal traces remain for analysis (step 432 G). If an additional signal trace remains to be evaluated, processing may return to calculation of the next signal tracei. The amplification and regeneration vote casting and positioning routine may exit upon an evaluation that no additional signal traces remain for evaluation (step 432H). The amplification and regeneration placement routine described is preferably executed in a forward and reverse light path traversal for all signal traces and amplification and regeneration stages may be designated for placement in a forward and/or reverse direction. It should be understood that amplification voting and regeneration voting, as described with reference to FIG. 14, may be performed sequentially or in parallel. Moreover, the automatic dispersion compensation routine may be performed as a subroutine of the regeneration voting procedure, that is the regeneration voting routine may include regeneration voting for placement of OEO and/or DCM regeneration components. [0109] After placement of any amplification and/or regeneration stages within the network design, an evaluation may then be made to determine if unnecessary regeneration and/or amplification stages exist that may be removed from the network design without adversely effecting the network performance. Electrical regeneration stages may first be designated for removal. After designation of a regeneration stage for removal, signal traces are recalculated to determine if additional amplification stage(s) are required as a result of removal of the regeneration stage. [0110] With reference now to FIG. 15, there is shown a flowchart depicting evaluation of removal of regeneration stages within the network design according to an embodiment of the present invention in accordance with step 430R of FIG. 12. Each regeneration stage of the network design is individually evaluated for removal from the network design and evaluation is initiated by designation of a first regeneration stagei for removal (step 432H). All signal traces are then re-calculated for the network design excluding the designated regeneration stagei (step 432I) and each recalculated signal trace is evaluated for an unacceptable OSNR (step 432J) or other distortion attributes. If it is determined that no recalculated signal traces have an unacceptable OSNR or other unacceptable distortion attribute, the regeneration stagei is permanently removed from the network design and processing continues by evaluating whether additional regeneration stages may be removed from the network design (step 432K). If, however, it is determined that any of the recalculated signal traces have an unacceptable distortion attribute after removal of the designated regeneration stage, designation for removal of the regeneration stagei is withdrawn and the regeneration stagei remains in the network design (step 432L). An evaluation of additional regeneration stages is then made (step 432K). If additional regeneration stages exist, a next regeneration stage may be designated for removal (step 432M) and processing may return to step 432H. Upon completion of evaluation of all regeneration stages for removal, it may be evaluated whether any regeneration stages were successfully removed from the network design (step 432N), that is whether any regeneration stages were removed without introducing unacceptable distortion attribute values of any signal traces. Removal of regeneration stage(s) from the network design may adversely effect power levels and, accordingly, if any regeneration stages are successfully removed, algorithm 10 may loop back to the amplification voting routine and evaluate signal traces for requisite amplification stages (step 432O) as aforedescribed with reference to FIG. 14. However, if no regeneration stages were successfully removed from the network design, the regeneration removal analysis may exit (step 432P). [0111] Necessity of amplification stages placed in the network design during the amplification voting and placement routine is next evaluated. Each amplifier is designated for removal from the network design and all signal traces are recalculated and re-evaluated for signal quality. Re-evaluation of the signal traces is performed by re-tracing the signal through appropriate light paths in the network design having the designated amplification stage removed therefrom. If the re-traced signals are determined to have sufficient power levels, the amplification stage designated for removal may then be removed from the network design. Alternatively, if any signal traces have calculated attributes indicating insufficient signal levels at any location in the network, the designation for removal of the amplification stage is withdrawn and the amplification stage remains in the network design. [0112] With reference now to FIG. 16, there is shown a flowchart depicting evaluation of removal of amplification stages within the network design in accordance with step 430S of FIG. 12. Each amplifier stage is individually evaluated for removal from the network design and evaluation is initiated by selection of a first amplifieri for removal (step 433A). All signal traces are then recalculated for the network design excluding the designated amplifieri (step 433B) and each recalculated signal trace is evaluated for an unacceptable attenuation (step 433C). If it is determined that no recalculated signal traces suffer an unacceptable power loss, the amplifieri is permanently removed from the network design and processing continues by evaluating whether additional amplification stages may be removed from the network design (step 433D). If, however, it is determined that any of the recalculated signal traces have insufficient power levels after removal of the designated amplification stage, the designation for removal of the amplifieri is withdrawn and the amplifieri remains in the network design (step 433E). An evaluation of additional amplifier stages is next made (step 433D). If additional amplifier stages exist, a next amplifier stage may be designated for removal (step 433F) and processing may return to step 433A. The amplification removal routine may exit upon evaluation of all designated amplification stages (step 433G). [0113] With reference now to FIG. 17, there is shown an optional variable optical amplification (VOA) subroutine that may be invoked by algorithm 10 to insure that maximum input power thresholds of any optical fiber amplifiers disposed within the network design are not exceeded in accordance with step 430T of FIG. 12. Modern optic networks may include one or more power band equalizers comprised of variable optical attenuators configured in a pre-amplifier stage such that optical signals are equalized across the wavelengths input into an optical fiber amplifier. Implementation of the VOA subroutine provides a technique ensuring, during network design, the highest possible signal level and OSNR are input into amplification stages without exceeding the input tolerances of the amplification stages according to an embodiment of the present invention. The VOA subroutine is initiated by calculating (or retrieving) signal traces from a network configuration previously selected (step 433H). The VOA subroutine is preferably executed subsequent to selection of a network configuration upon completion of evaluation of removal of amplification stages as described hereinabove with reference to step 430S as described with reference to FIG. 16. Maximum input power tolerance(s) are next retrieved for the optic fiber amplifieri designated for placement in the selected network configuration (step 433I). Thereafter, an analysis of all signal traces having the optic fiber amplifieri included within their respective light path are analyzed to determine if the signal level of any signal traces exceed the input tolerance of the optic fiber amplifieri (step 433J). If no signal traces are determined to have signal levels in excess of the input of the optic fiber amplifieri, an evaluation of whether additional optic fiber amplifiers are designated for placement within the network design is made (step 433L). Processing may return to retrieval of the input power tolerance of optic fiber amplifieri if any optic fiber amplifier stages remain. Otherwise, the network design may be finalized (step 4330). If, however, it is determined at step 433J that an input power tolerance of the optic fiber amplifieri is exceeded, an attenuation setting of a power band equalizeri disposed as a pre-amplification stage of optic fiber amplifieri may be adjusted (step 433M) and an analysis of whether the increment to the power band equalizeri exceeds operational capabilities thereof is made (step 433N). If the adjusted attenuation setting of the power band equalizeri is within the operational range of the equalizer, processing may return to step 433H and signal traces may be re-calculated for the network design. The amount of adjust made to the attenuation level of the equalizeri may be dependent on the particular wavelength being attenuated. Other techniques for adjusting the attenuation level of the equalizer are possible. Processing may return to evaluation of additional optic fiber amplifiers if the operation limits of the power band equalizer are exceeded (step 433L). [0114] Returning again to FIG. 6, algorithm 10 evaluates whether a lower cost routing and wavelength assignment is available after iteratively performing the described automatic equipment engineering subroutine, that is algorithm 10 evaluates whether a lower cost network design may be developed by varying the RWA (step 435). Various techniques may be employed to evaluate the impact of alternative RWA assignments on the network design cost. For example, algorithm 10 may employ a conjugate gradient algorithm to search for a wavelength route reassignment that will yield a reduction in the cost of the network design. Such a process may be performed iteratively until no additional cost reduction is attained or may alternatively be iteratively performed a pre-defined number of repetitions. Other techniques may be substituted for a conjugate gradient algorithm technique of RWA reassignments, such as simulated annealing, neural network algorithms, and/or other techniques. [0115] In FIG. 18, there is a simplified flowchart of algorithm 10 processing that may be performed to evaluate RWA reassignment and the effect on the overall cost of the network design. The total equipment cost determined from the equipment selection made after iteratively performing equipment provisioning and optical path analysis may be input into the conjugate gradient algorithm and alternative RWAs may be generated and associated cost (C) values determined therefor (step 436). A comparison between the total equipment cost for each alternative RWA may be compared with the total equipment cost of the current network design and an evaluation of whether a reduction in the network cost is made (step 437). If a reduction in the network cost is achieved by an alternative RWA, the network equipment provisioned for the network design is reconfigured according to the alternative RWA (step 438). For example, the site information data structures may be re-generated or modified, the site cost matrix may be updated, and/or other data structures may be modified, re-generated, or otherwise altered to reflect a modification to the network design required to achieve the alternative RWA. Algorithm 10 processing may then return to the iterative automatic equipment engineering subroutine and, thereafter, return to performing additional RWA iterations until a reduction in the network cost is not attained. Thereafter, algorithm 10 processing may terminate (step 440). In an alternative technique, traffic demands may be reiteratively assigned to various wavebands, rather than wavelengths, and the impact of network performance and cost may be similarly determined. [0116] With reference now to FIG. 19, there is shown an exemplary signal trace 33 that may be output by algorithm 10 that graphically illustrates a modeled signal for a particular network configuration having equipment components designated for placement in each site of the network design. The exemplary signal trace 33 comprises a signal plot 500 and may comprise various site and/or component identifiers 505A-505S that are associated with particular plot points 500A-500S. The exemplary signal trace 33 illustrates a modeled signal for a wavelength being added at a site 1 identified by component identifier 505A. A signal modeled by signal trace 33 is then passed through a post amplifier, a combiner and an FPP prior to being conveyed across a first fiber link and conveyed to another FPP of a regeneration component. Thereafter, the modeled signal is passed through an equalizer, an amplification and a post-amplification stage, a combiner and an FPP before being conveyed on a second fiber link and transmitted to a second site. [0117] Each particular plot point 500A-500S has a calculated signal level associated therewith. In the exemplary signal trace 33, plot points 500A-500S are plotted with respect to a signal value in decibels milli-Watts (dBm). Each component identifier 505A-505S may have a respective loss or gain identifier 510A-510S that provides a description of a respective signal loss or gain associated with a signal plot point 500A-500S. The exemplary signal trace 33 provides signal plot points for a modeled signal conveyed through various components of a first site (points 500A-500F), through a fiber link (point 500G), through a regeneration component (points 500H-500L), through another interconnecting fiber link (point 500M), and through various components of a second site (points 500 N-500S). As shown, the signal trace preferably includes calculation of an attenuation or gain incurred through various signal �penalties� applied to the calculated signal level attribute of signal trace 33. [0118] As aforedescribed, signal trace 33 may have one or more attributes, such as a power level attribute and any one or more of various distortion attributes, calculated at discrete locations (such as inputs and/or outputs of network components) of the network design. In a preferred embodiment, each of the power level attributes and the distortion attribute(s) have a mean and variance value calculated at each location for which signal trace 33 plot points are calculated. Thus, plot 500 may represent a mean power level calculated for signal trace 33. The mean of a calculated signal trace attribute is preferably calculated by employing statistical techniques and incorporates component performance variances in developing a power level attribute distribution. For example, each of plot points 500A-500S may be calculated as Gaussian distribution functions. Because component performance characteristics are statistically independent, the variances and/or means thereof may be summed (for gains), or alternatively subtracted (for losses), from point-to-point to determine variances and/or means of a particular plot point 500A-500S of signal trace 33. For example, to determine the mean power level of the combiner (identifier 505K), that is to determine the value of signal trace point 500K, the mean power level of point 500J (corresponding to the mean power level at a post amplification stage designated by identifier 505J) is summed with the mean loss of the combiner stage corresponding to point 500K. While the signal trace 33 is representative of a signal trace power attribute, a similar signal trace may be developed for any distortion attributes, such as jitter, crosstalk, PMD, chromatic dispersion, or another distortion attribute, for which associated component performance parameters are known or otherwise obtainable. Preferably, signal trace(s) generated for distortion attributes are likewise generated as mean distortion values. [0119] In addition to plot 500 of a signal trace attribute, a graphical output may include a plot 525 (illustratively denoted with dashed lines) of a network design criteria. Plot 525 may be generated by plotting input requirements of each network component included in the network design. Thus, by calculating the signal variance of any signal trace 33 plot point, a probability of satisfactory network design performance at that network position may be had. Advantageously, statistical design points may be defined prior to network design such that a network design is generated that provides a desired statistical performance. For example, a statistical design point of plot 525 may be defined for an optical path that may be disposed within a network to be designed such that the optical characteristics of a generated network design will meet the statistical design criteria. Thus, the network designer can specify a numerical probability of proper operation of an optical path that is desired and algorithm 10 is constrained thereby such that any selected network configuration will meet, or exceed, the statistical design criteria for the optical system. Specification of a statistical design point for a particular component may be defined by equation 9.
[0120] where SDP is the statistical design point and σ2 is the variance. [0121] As mentioned hereinabove, algorithm 10 may provide various outputs to an operator thereof. For example, an optimized network map 30 detailing network design sites, network components selected for population of various network sites, and graphical indications of RWAs may be visually summarized in a visual output. Other outputs, such as network layer specifications 31 detailing network site and connectivities therebetween, listings of equipment 32 selected for deployment within the selected network design, as well as visual output of signal trace(s) 33. Algorithm 10 may provide various other outputs as well. For example, cost optimization bar graphs may be generated by algorithm 10 that provide an effective and intuitive demonstration of network cost savings obtained through analysis of various network design configurations. [0122] With reference to FIG. 20, there is shown a cost optimization bar chart 800 that may be generated by algorithm 10 and displayed on an output device, such as a cathode ray tube or another display device. The exemplary bar chart 800 is displayed within a graphical user interface provided by a windowing computer system, as is conventional. Bar chart 800 may include a plurality of graphical bars 810-813. An x-axis may specify a particular network configuration and the y-axis may specify the cost of the configuration. Each graphical bar 810-813 may be graphically partitioned into respective subregions 810A-810D - 813A-813D. As described hereinabove, during network design and reconfiguration, individual network components may be selected for placement within the network design and a cost effect of the selection is analyzed. For example, a network cost may be calculated by summing site cost matrices. Site cost matrices are generated by indexing unit (component) prices from a unit price matrix and multiplying the unit price by the number of the associated units selected for the site. Accordingly, the cost of a site is calculated by performing such a routine for each component model selected for the site. As aforedescribed, each network component is categorized according to a general functional type or class. Component class costs may be developed in a manner similar to site costs, namely by multiplying the unit price cost of each component selected from a particular class with the number of that particular component models selected for placement within the network. The numerical value of a component class costs may be converted to a graphical relation and displayed in bar chart 800. In the illustrative example, subregions 810A-813A are graphical representations of optical amplification class costs in a network design and subregions 810B-813D may be representative of transmission card-class components. Similarly, subregions 810C-813C and 810D-813D may be representative of a particular component class cost, such as fiber-class components, tributary card-class components, or other functionally categorized component classifications. Textual and/or numerical information may be provided in conjunction with bar chart 800 to facilitate an easy understanding of the information conveyed to the user. For example, each subregion 810A-810D-813A-813 d may have a numerical dollar value included for display within the respective subregion that indicates the dollar amount of all components selected for a particular network configuration from a common equipment class. Numerical identifiers 830-833 may be associated with a particular bar and identify a particular network configuration so that reductions and/or increases in a component-class from one network configuration to another may be easily determined by the user. The cost optimization bar chart 800 is exemplary only and various such graphical outputs for facilitating an understanding of the impact of various network configurations on a network cost are possible. Similarly, graphical output illustrative of RWA variations on the network cost may be generated by algorithm 10. [0123] With reference now to FIG. 21, there is a block diagram of computer system 900, or another apparatus operable to execute a computer-readable instruction set, that may be used to execute algorithm 10 and the various subroutines thereof. Computer system 900 stores algorithm 10 in a memory unit 940. Through conventional techniques, algorithm 10 is executed by an operating system 950 and one or more conventional processing elements 955 such as a central processing unit. Operating system 950 performs functionality similar to conventional operating systems, controls the resources of computer system 900, and interfaces the instructions of algorithm 10 with processing element 955 as necessary to enable algorithm 10 to properly run. [0124] Processing element 955 communicates to and drives the other elements within computer system 900 via a local interface 960, which may comprise one or more buses. Furthermore, an input device 965, for example a keyboard or a mouse, can be used to input data from a user of computer system 900. A disk storage device 980 can be connected to local interface 960 to transfer data to and from a nonvolatile disk, for example a magnetic disk, optical disk, or another device. An output device, such as a printer, cathode ray tube, or another display device, may provide output generated from execution of algorithm 10 by processing element 955 to the user of computer system 900 and algorithm 10. [0125] As described, the present invention provides a computer-aided optical network design that facilitates minimization of wavelength usage and optimization of waveband grouping and sequencing during network design. The present invention models light path characteristics and corresponding signal losses by generation of signal traces to facilitate a network configuration featuring the most economical cost for specified network performance requirements. Calculation and analysis of signal traces provide a technique for determining performance and cost effects of different network components. By varying the light path characteristics of the network design configuration, the impact on overall network performance and cost is evaluated. Minimization of wavelength usage facilitates a reduction in equipment costs at the optical layer by reducing the number of requisite lasers, detectors, and common equipment. Moreover, automated placement of amplification and/or regeneration components within the network design is facilitated by modeling optical signal deterioration that may include signal loss, noise accumulation, and dispersion effects. [0126] While the invention has been particularly shown and described by the foregoing detailed description, it will be understood by those skilled in the art that various changes, alterations, modifications, mutations and derivations in form and detail may be made without departing from the spirit and scope of the invention. Referenced byCiting PatentFiling datePublication dateApplicantTitleUS6782159 *May 23, 2003Aug 24, 2004Tropic Networks Inc.Method for determining optimal location and value of dispersion compensation modules in an optical networkUS6829406 *Oct 21, 2002Dec 7, 2004Tropic Networks Inc.Method and system for determining location and value of dispersion compensating modules in an optical networkUS7020394 *Aug 17, 2001Mar 28, 2006Quantum Bridge Communications, Inc.Method and apparatus for path selection and wavelength assignment in an optical networkUS7096176 *Apr 11, 2001Aug 22, 2006AlcatelOptical route design system and method for analyzing the performance of an optical fiber transmission pathUS7146000 *Jan 25, 2002Dec 5, 2006Level (3) CommunicationsRouting engine for telecommunications networkUS7218851 *Sep 18, 2002May 15, 2007Sprint Communications Company L.P.Communication network design with wavelength convertersUS7289731 *Jan 29, 2004Oct 30, 2007Alcatel LucentOptical network termination with automatic determination of geographic locationUS7382979 *Dec 27, 2005Jun 3, 2008Fujitsu LimitedWavelength dispersion compensation design method and a system thereofUS7415208 *Mar 20, 2003Aug 19, 2008Ciena CorporationMethod and system for allocating bandwidth in an optical communication networkUS7466688 *Sep 5, 2003Dec 16, 2008Alcatel-Lucent Usa Inc.Routing and design in K-shared networkUS7526205 *Apr 14, 2003Apr 28, 2009Azea Networks LimitedTransmission systemUS7558284 *Apr 4, 2005Jul 7, 2009Fujitsu LimitedNetwork design deviceUS7577576 *Oct 31, 2003Aug 18, 2009Walter BaechtigerNetwork branch placement toolUS7590350 *Sep 2, 2003Sep 15, 2009Nortel Networks LimitedSystem and method for automated engineering of optical networksUS7610361 *Jan 5, 2004Oct 27, 2009At&T Intellectual Property I, L.P.System and method for ethernet network designUS7623785 *Dec 28, 2006Nov 24, 2009Verizon Services Corp.DWDM optical network planning methodUS7646983 *Mar 10, 2009Jan 12, 2010Tyco Telecommunications (Us) Inc.Apparatus and method for commissioning an optical transmission systemUS7660527 *Aug 8, 2006Feb 9, 2010Fujitsu LimitedOptical network design methodUS7693422 *Sep 28, 2004Apr 6, 2010Alcatel-Lucent Usa Inc.Constraint-based design of optical transmission systemsUS7715721 *Dec 12, 2001May 11, 2010Alcatel-Lucent Usa Inc.Wavelength assignment in an optical WDM networkUS7738787 *Jul 18, 2007Jun 15, 2010Fujikura Ltd.Optical transmission line monitoring device, optical transmission line monitoring method, and computer programUS7751345 *Apr 30, 2007Jul 6, 2010Fujitsu LimitedOptical network design method and storage medium for storing design programUS7778202 *Aug 31, 2007Aug 17, 2010Tellabs Operations, Inc.Method and apparatus to provision network routesUS7894446 *Nov 23, 2005Feb 22, 2011Jds Uniphase CorporationMethod and systems for optimization analysis in networksUS7904848 *Mar 13, 2007Mar 8, 2011ImecSystem and method for runtime placement and routing of a processing arrayUS7929861 *Mar 30, 2010Apr 19, 2011Alcatel-Lucent Usa Inc.Wavelength assignment in an optical WDM networkUS7978973Apr 28, 2009Jul 12, 2011Xtera Communications Ltd.Transmission systemUS8000250 *Sep 27, 2005Aug 16, 2011At&T Intellectual Property Ii, L.P.Method for routing optical signals with diversity requirementsUS8144598Sep 4, 2009Mar 27, 2012Level 3 Communications, LlcRouting engine for telecommunications networkUS8145056 *Jul 15, 2008Mar 27, 2012Futurewei Technologies, Inc.Distributed wavelength conversion control for signaling protocolsUS8149714Dec 4, 2006Apr 3, 2012Level 3 Communications, LlcRouting engine for telecommunications networkUS8155009Sep 4, 2009Apr 10, 2012Level 3 Communications, LlcRouting engine for telecommunications networkUS8185422 *Jul 31, 2006May 22, 2012Accenture Global Services LimitedWork allocation modelUS8185655 *Dec 3, 2008May 22, 2012At&T Intellectual Property I, L.P.Maximizing diversity in a subset of elements utilizing GRASP with path relinkingUS8213793 *Sep 28, 2007Jul 3, 2012Verizon Patent And Licensing Inc.Wavelength assignment optimizationUS8214237 *Aug 9, 2007Jul 3, 2012Intel CorporationMethods and apparatus for resource allocation in computer architecturesUS8238252Sep 4, 2009Aug 7, 2012Level 3 Communications, LlcRouting engine for telecommunications networkUS8239502 *Jul 13, 2009Aug 7, 2012At&T Intellectual Property I, L.P.System and method for network designUS8306839Aug 28, 2009Nov 6, 2012Accenture Global Services LimitedLabor resource decision support systemUS8392111 *Aug 3, 2007Mar 5, 2013Samsung Electronics Co., Ltd.Navigation method, medium, and systemUS8451979Jun 4, 2001May 28, 2013Calix, Inc.System for correlating a subscriber unit with a particular subscriber in a passive optical networkUS8468043 *Apr 13, 2009Jun 18, 2013At&T Intellectual Property I, L.P.Networks with redundant points of presence using approximation methods and systemsUS8498889 *Nov 13, 2011Jul 30, 2013Emcien, Inc.Product configuration modeling and optimizationUS8504403Sep 13, 2012Aug 6, 2013Accenture Global Services LimitedLabor resource decision support systemUS8588607 *Jan 29, 2009Nov 19, 2013Hewlett-Packard Development Company, L.P.Dispersion scheme for physical layer diagnosis in bi-directional dual-fiber optical networksUS20080033636 *Aug 3, 2007Feb 7, 2008Samsung Electronics Co., LtdNavigation method, medium, and systemUS20090276510 *Jul 13, 2009Nov 5, 2009At&T Intellectual Property I, L.P.System and Method for Network DesignUS20100138373 *Dec 3, 2008Jun 3, 2010Resende Mauricio Guilherme DeMaximizing Diversity in a Subset of Elements Utilizing GRASP With Path RelinkingUS20120114329 *Jan 13, 2012May 10, 2012Futurewei Technologies, Inc.Optical Impairment Aware Path Computation Architecture in PCE Based NetworkUS20120275789 *Oct 28, 2011Nov 1, 2012Telcordia Technologies, Inc.System and method for automated provisioning of services using single step routing and wavelength assignment algorithm in dwdm networksUS20130202299 *Mar 15, 2012Aug 8, 2013Ciena CorporationPath computation systems and methods in optical networksEP2109971A1 *Jan 31, 2008Oct 21, 2009Level 3 Communications, LLCNetwork configuration optimizationWO2008097807A1Jan 31, 2008Aug 14, 2008Level 3 Communications LlcNetwork configuration optimizationWO2013164044A1Dec 27, 2012Nov 7, 2013Deutsche Telekom AgMethod and device for constructing and operating a modular, highly scalable, very simple, cost-efficient and sustainable transparent optically-routed network for network capacities of greater than 1 petabit(s)* Cited by examinerClassifications U.S. Classification398/79International ClassificationH04L12/24, H04L12/26, H04J14/02Cooperative ClassificationH04J14/0241, H04L41/0826, H04L41/22, H04J14/0284, H04L41/145, H04J14/0227, H04J14/0283European ClassificationH04L41/14B, H04L41/22, H04L41/08A3A, H04J14/02MLegal EventsDateCodeEventDescriptionJun 10, 2013ASAssignmentEffective date: 20130607Owner name: GLOW NETWORKS, INC., TEXASFree format text: RELEASE BY SECURED PARTY;ASSIGNOR:SILICON VALLEY BANK;REEL/FRAME:030620/0655Free format text: RELEASE BY SECURED PARTY;ASSIGNOR:SILICON VALLEY BANK;REEL/FRAME:030620/0812Jul 1, 2005ASAssignmentOwner name: SILICON VALLEY BANK, CALIFORNIAFree format text: SECURITY INTEREST;ASSIGNOR:GLOW NETWORKS, INC.;REEL/FRAME:016733/0984Effective date: 20050613Nov 4, 2002ASAssignmentOwner name: SILICON VALLEY BANK, CALIFORNIAFree format text: SECURITY INTEREST;ASSIGNOR:GLOW NETWORKS, INC.;REEL/FRAME:013452/0243Effective date: 20020117Sep 18, 2002ASAssignmentOwner name: GLOW NETWORKS, INC., TEXASFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:EGNER, WILL A.;MALLAPU, VINAY KUMAR REDDY;ZHENG, YINDONG;REEL/FRAME:013303/0203Effective date: 20020607RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services©2012 Google