Abstract:
The introduction of automation of testing configuration and the extensive use of protocol adaptation to provide a consistent user interface for a test apparatus across multiple vendor implementations through the use of programmable adapter modules facilitates systematic and efficient testing. Proper functionality of a given optical switch implementation, quantification of a system&#39;s parameters, and determination of switching performance measures can be obtained.

Description:
This application claims priority to, and is a continuation of, co-pending U.S. patent application Ser. No. 10/892,072, filed Jul. 15, 2004, entitled “METHODS AND APPARATUS FOR AUTOMATED TESTING AND ANALYSIS OF DENSE WAVE DIVISION MULTIPLEXING (DWDM) SWITCHING DEVICES,” which co-pending application is incorporated by reference herein in its entirety. 

   FIELD OF THE INVENTION 
   The present invention relates generally to the field of optical communications systems and, more particularly to the field of automated testing of Dense Wave Division Multiplexing (DWDM) optical switches and analysis of test results. 
   BACKGROUND 
   Dense Wave Division Multiplexing (DWDM) is a technology that is increasing in popularity among communications technology leaders in finance, healthcare, government and education research thus impacting the future deployment plans of large communications service providers. The deployment of DWDM technology can increase the capacity over existing optical communications links and networks, e.g., those using single mode fiber, while adding network flexibility to allow for the almost instant adjustment and/or expansion in bandwidth at points in the network where needed. 
   DWDM technology involves the packing of multiple wavelengths of light onto a single physical fiber thus providing a large multiplexing factor over standard single mode fiber. The multiplexing of multiple wavelengths onto a single physical interface has led to the possibility of routing and switching at the wavelength level across various stages of a network permitting a more efficient use of the total bandwidth by providing the capability to dynamically allocate resources as needed. 
   Recent advances in switching technology for optical systems have made service provider deployment of these DWDM technology systems more realistic, resulting in the need to test these systems and system components against performance benchmarks to validate the claims of a given manufacturer and comparatively evaluate similar equipment from different manufactures. It is in the interest of communication service providers, who select, purchase, deploy, and use DWDN switching elements from various manufactures, to characterize accurately a system&#39;s performance, before the introduction of a new network element into the network. It would also be advantageous if these tests could be performed in an automated, systematic, cost effective, and as speedy a manner as possible. Furthermore, while optical switching systems and elements from various manufactures operate roughly in the same manner in principle, in reality, many of the vendors rely on proprietary protocols, particularly over their control and/or test interfaces, that make testing very difficult and cumbersome. Seemingly identical tasks have to be mapped out differently for each vendor&#39;s device, and the testing has to be repeated manually. In addition, the testing devices have to be re-programmed individually to fit the specific requirements, e.g., number of ports, dynamic ranges, operational optical interfaces, control/test interface(s), control/test protocol, and test options, corresponding to a given vendor device. 
   In view of the above discussion, it is apparent that there is a need for methods and apparatus to provide an integrated testing tool that packages a number of hardware and software components, as well as protocol adapters for each vendor&#39;s technology. Methods and apparatus that supply an analytical engine that permits automatic test configuration set up, test execution, collection of test results and analysis of these results, presenting them to the tester in a unified manner, e.g., a Graphical User Interface (GUI)-based interface, would also be beneficial. Communication system service providers can benefit from cost effective and timesaving tools that will more efficiently allow the evaluation and testing of new DWDM network elements, from various vendors, before these elements are introduced into the network. In addition, as various deployed DWDM elements age, system and/or performance parameters may degrade. An automated, well controlled testing system with data retention capability would allow for periodic testing and evaluation of deployed devices to identify potential degradations and allow corrective actions to be taken before critical parameters exceed allowable limits. 
   SUMMARY 
   Various features of the present invention are directed to methods and apparatus for testing and analyzing that permits verification of the performance of a DWDN optical switch device in a computer controlled, automated environment for multiple vendor implementations. The DWDN testing and analysis apparatus of the present invention offers a solution to the difficulties in verifying the function and performance of a DWDN optical switching device in a systematic and efficient manner across multiple vendors. Embodiments of the present invention provide automation of the testing configuration and extensively use protocol adaptation across multiple vendor implementations through the use of conversion modules programmed and software-integrated into the analysis engine tool. Features of the present invention include testing methodology that may be used to verify the proper functioning of a given optical switch implementation. This verification also includes the quantification of a system&#39;s parameters and determination of switching performance measures, e.g. timing. Additionally, in some embodiments, capabilities are built into the analysis engine, of the present invention, for the determination of Service Level Agreement (SLA) parameters that can be provided for the optical layer or as input to calculations of SLA at higher-level protocols. 
   New vendors&#39; products can be promptly evaluated in a shorter time interval by using the present invention, over the time presently required to perform an equivalent evaluation using presently employed methods and apparatus. This increase in the speed of an evaluation, provided by the present invention, represents significant value added by this invention in terms of time savings, manpower savings. In addition, by providing a more systematic, controlled, and efficient DWDM wavelength switch testing approach, a service provider may obtain a better comparative evaluation, test a larger sample of switches, and track changes, e.g., degradations in deployed switches over time. 
   Various system parameters that can be measured, examined, compared, and evaluated through testing, in accordance with various embodiments of the present invention, include:
         1. Switch timing
           Switching time   Switching Speed (number of switches per second)   Full Switch Capacity   
           2. Spectral Attenuation   3. Insertion Loss   4. Chromatic Dispersion   5. Polarization Mode Dispersion (PMD)   6. Polarization Dependent Loss (PDL)   7. Optical Return Loss (ORL)   8. Optical Power Range (e.g., maximum/minimum optical power per port)   9. Isolation   10. Directivity   11. Cross-talk Adjacent Channels   12. Cross-talk Non-adjacent Channels       

   Additionally, performance parameters that can be measured through testing, in accordance with various embodiments of the invention include:
         1. Bit-error rate (BER)   2. Optical Signal-to-Noise Ratio (OSNR)       

   Currently, the few available testing systems used to obtain measurements on the above parameters consist of a collection of devices that are used largely in a manual fashion and are, therefore, cumbersome and extremely time-consuming to use. Furthermore, because of the nature of the optical systems available today, the interfaces to the optical switching devices are proprietary and therefore the associated testing devices are custom designed for a particular manufacturer&#39;s system and are typically not reusable to test another manufacturer&#39;s device. 
   The invention is directed toward methods and apparatus obtaining measurements of the above parameters in an automated, user friendly, and time efficient fashion in a well controlled testing environment. 
   Various embodiments of the present invention, are directed toward an Integrated Testing and Analysis System for a Wavelength Selective Switch (ITASWSS) that include the following component modules: 
   Wavelength Generators 
   Wavelength Detectors 
   Internal Switching Device(s) 
   BER/OSNR Testing Modules 
   Multiple Protocol Adapters 
   An Analytical Engine 
   In some embodiments, of the present invention, the testing system used to evaluate an optical switching device, e.g., a DWDM wavelength switch, uses a dual ITASWSS testing configuration, with a first ITASWSS being used for wavelength generation at the originating end and a second ITASWSS acting as a wavelength analyzer at the target end. 
   In some embodiments, the first ITASWSS may act as a master, controlling and synchronizing testing overall operations, while the second ITASWSS may act as a slave, responding to direction from the first ITASWSS. Signals, e.g., modulated information on wavelengths are generated, grouped together, and launched at the originating end by the first ITASWSS. The signals, grouped into multimode sets, are routed into the wavelength switch, e.g., through multiple input ports, each input port supporting many, e.g., 10, 20, 40 or more wavelengths (virtual channels). The wavelength switch may switch information onto different wavelengths, switch wavelengths, and group wavelengths as multimode sets onto designated output ports. The wavelength switch operation is controlled by the first ITASWSS. At the target end, the output signals from the wavelength switch are input to the second ITASWSS. The second ITASWSS receives the signals which have been processed by the wavelength switch. The second ITASWSS performs detection and information recovery on the received signals. The ITASWSSs of the testing system can determine what portion of the launched signals and information was able to traverse the switch under what conditions. The ITASWSSs of the testing system can determine how the signals and information were altered, e.g., degraded, due to traversing the wavelength switch, and under what conditions. This testing may be performed automatically in stages to fine tune the granularity of the measurements. 
   In some embodiments, ITASWSSs are implemented with additional capabilities such as: establishing SLA benchmarks at the physical (optical) layer, developing estimations about the impacts that the measured optical switching impairments may have on higher level protocols, retaining a database of information on tested switches, generating comparison reports. 
   The ITASWSS, in accordance with the invention, is easily updated to allow for new variations of wavelength switches and new protocols which may be employed. 
   In some testing embodiments, a single ITASWSS performs both test signal origination functions, test signal detection function, and evaluation functions, and a second ITASWSS is not used to evaluate a wavelength switch. 
   In some embodiments, the testing system may include the capability to test and evaluate other system component and, or sets of components used in DWDM networks, e.g., multimode fiber cables, splitters, attenuators, gain devices, repeaters, transmitters, receivers, etc. 
   In some embodiments various features of the present invention are implemented using modules. Such modules may be implemented using software, hardware or a combination of software and hardware. Many of the above described methods or method steps can be implemented using machine executable instructions, such as software, included in a machine readable medium such as a memory device, e.g., RAM, floppy disk, etc. to control a machine, e.g., general purpose computer with or without additional hardware, to implement all or portions of the above described methods, e.g., in one or more nodes. Accordingly, among other things, the present invention is directed to a machine-readable medium including machine executable instructions for causing a machine, e.g., processor and associated hardware, to perform one or more of the steps of the above-described method(s). 

   
     BRIEF DESCRIPTION OF THE FIGURES 
       FIG. 1  is a drawing illustrating an exemplary dual Integrated Testing and Analysis System for Wavelength Selective Switch (ITASWSS) configuration test system for testing and analyzing DWDM wavelength switches, in accordance with the present invention. 
       FIG. 2  is a more detailed representation of an exemplary ITASWSS unit implemented in accordance with the present invention. 
       FIG. 3  is a more detailed representation of an exemplary memory that may be used in an exemplary ITASWSS unit, implemented in accordance with the present invention. 
       FIG. 4  is a flowchart of an exemplary method of operating an exemplary automated DWDM wavelength switch testing system in accordance with the present invention. 
   

   DETAILED DESCRIPTION 
     FIG. 1  is a drawing illustrating an exemplary test system  100  implemented in accordance with the present invention and using methods of the present invention. Exemplary test system  100  includes a first Integrated Testing and Analysis System for Wavelength Selective Switch (ITASWSS)  102  coupled to a DWDM wavelength switch  104 , a second ITASWSS  102 ′, and a user interface device  106 . ITASWSS # 1   102  includes a first optical output interface port  108 , a second optical interface output port  110 , a user I/O port  112 , a switch control interface port  114 , an ITASWSS/ITASWSS port  116 , a first optical interface input port  118  and a second optical interface input port  120 . DWDM wavelength switch  104  includes a switch control interface port  122 , a software control/status module  124 , an optical switch module  126 , a first optical input interface port  128 , a second optical input interface port  130 , a first optical interface output interface port  132 , and a second optical interface output port  134 . ITASWSS# 2   102 ′ includes a first optical input interface port  118 ′, a second optical interface input port  120 ′, an ITASWSS/ITASWSS interface port  116 ′, a switch control interface port  114 ′, a user I/O port  112 ′, a first optical output interface port  108 ′, and a second optical output interface port  110 ′. 
   The exemplary DWDM wavelength switch  104  is the unit under test, e.g., a specific vendor&#39;s optical switching device being evaluated. ITASWSS # 1   102 , being used as a test signaling source and test controlling device, is coupled to the DWM wavelength switch  104  via optical link  136 . ITASWSS# 2   102 ′, being used as a test signaling receiver is coupled to DWM wavelength switch  104  via optical link  138 . Optical links  136 ,  138  may be, e.g., multimode optical fibers, with connectors at each end allowing coupling to an optical port,  108 ,  110 ,  128 ,  130 ,  132 ,  134 ,  118 ′,  120 ′,  108 ,  110 ′. In system  100  optical link  136  couples port  108  to port  128 , and optical link  138  couples port  132  to port  118 ′. Switch control interface ports  114 ,  122  are coupled together via bus  140  over which wavelength switching control signals, responses, and test information may flow. Signaling through bus  140  uses a protocol instruction set specific to the optical wavelength switch  104  under test. Switch control signaling received through port  122  is directed to the switch control/status module  124  which processes the command instructions and controls the operation of the optical switch module  126 . Optical switch module  126 , when commanded, switches for a plurality of wavelengths, received information signals modulated on one wavelength to a different wavelength. 
     FIG. 1  shows five exemplary input test signals ( 142 ,  144 ,  146 ,  148 ,  150 ) being conveyed from ITASWSS # 1   102  in multimode fiber  136  to wavelength switch  104 . Five exemplary output test signals ( 152 ,  154 ,  156 ,  158 ,  160 ) are conveyed from wavelength switch  104  to ITASWSS #  2   102 ′ via multimode optical fiber  138 . Each wavelength may be viewed as a virtual channel acting as a separate pipe for conveying information. Sets of information to be conveyed may be modulated on each wavelength, by ITASWSS #  1   102 . First input test signal  142  represents information set  1  modulated on wavelength  1 ; second input test signal  144  represents information set  2  modulated on wavelength  2 ; third input test signal  146  represents information set  3  modulated on wavelength  3 ; fourth input test signal  148  represents information set  4  modulated on wavelength  4 ; fifth input test signal  150  represents information set  5  modulated on wavelength  5 . The optical switch module  126  interchanges, e.g., swaps or remaps information sets between the wavelengths as directed by switch control/status module  124 . For example, in  FIG. 1 , first output test signal  152  represents information set  4  modulated on wavelength  1 ; second output test signal  154  represents information set  5  modulated on wavelength  2 ; third output test signal  156  represents information set  2  modulated on wavelength  3 ; fourth output test signal  158  represents information set  1  modulated on wavelength  4 ; and fifth output test signal  160  represents information set  3  modulated on wavelength  5 . 
   ITASWSS # 2   102 ′ receives the output signals  152 ,  154 ,  156 ,  158 , and  160 , via optical input interface port  118 ′, and evaluates the received signals in terms of system and performance criteria, e.g., switching rate, attenuation, error rate, etc. 
   ITASWSS # 2   102 ′ conveys raw measurement information and/or evaluation information, e.g., system and performance related parameters, to the ITASWSS#  1   102  out through ITASWSS/ITASWSS interface port  116 ′ over bus  162  to ITASWSS/ITASWSS interface port  116 . In some embodiments, ITASWSSs  1  and  2  ( 102 ,  102 ′) shall operate in a master/slave relationship. For example, ITASWSS # 1   102  may control testing operations, e.g., test sequence, test configuration, test timing, etc., and may send configuration and timing synchronization messages to ITASWSS # 2   102 ′ over bus  162 . 
   User I/O interface  112  in ITASWSS  1   102  is coupled via bus  164  to the user interface device  106 . The user interface device  106 , e.g., a personal computer station including a graphical interface capability, allows a test operator to input configuration information on the unit under test, DWMD wavelength switch  104 , e.g. vendor, model number part number, S/N, etc., so the ITASWSS # 1   102  may properly configure with the appropriate protocols to be able to command signaling and receive status information in communications with the wavelength switch  104 . User interface device  106  also provides the user with a menu to select and command various options of automated test sequence commands to conduct the evaluation. Test results may be provided to the user in a graphical format. 
   Although the exemplary system  100  is shown with one optical link  136  connecting ITASWSS # 1   102  to wavelength switch  104 , and one optical link  138  connecting wavelength switch  104  to ITASWSS # 2   102 ′, in general, a plurality of optical input and output links, e.g., multimode fibers, may be used to couple a plurality of optical communication ports on devices  102 ,  104 , and  102 ′. Signals output from ITASWSS # 1   102  may be output over ports  108  and  110 . The wavelength switch  104  which may receive signals over ports  128 ,  130  may pass signals directly through, may interchange modulated information on wavelengths, may move modulated information to different wavelengths, e.g. the input set of wavelengths (virtual channels) need not be the same as the output set of wavelengths. The wavelength switch  104  may output duplicate sets of input information in multiple output signals. In addition, wavelength switch  104  may intermingle some information and/or signals received on different input ports  128 ,  130  such that optical output port  132  conveys some of the information received on input port  128  and some of the information received on input port  130  while optical output port  134  conveys some of the information received on port  128  and some of the information received on port  130 . 
   In some embodiments, a single ITASWSS  102  is used for wavelength switch  104  testing and evaluation. In such an embodiment, optical input ports  118 ,  120  may be used in place of optical input ports  118 ′,  120 ′, and the receiver detection, measurement, and evaluation modules in ITASWSS  102  shall be used in place of the modules in ITASWSS  102 ′. 
   In  FIG. 1 , switch control interface port  114 ′ and user I/O interface  112 ′ are shown as being unused. In some embodiments, switch control interface port  102 ′ may also be coupled to bus  140 , e.g., to monitor control signaling and use such information for configuration purposes. In some embodiments, the user I/O interface  112 ′ may be coupled to user interface device  106  or to another user interface device, e.g., to allow operations and results pertaining to ITASWSS  2   102 ′ to be monitored without having such information conveyed through the ITASWSS/ITASWSS ports  116 ,  116 ′. 
     FIG. 2  is a more detailed drawing of an exemplary ITASWSS  200  implemented in accordance with the present invention and using methods of the present invention. Exemplary ITASWSS  200  may be used as ITASWSS # 1   102  and/or ITASWSS # 2   102 ′ in system  100  of  FIG. 1 . Exemplary ITASWSS  200  includes an analytical engine module  202 , a protocol adaptor module  204 , a wavelength generator module  206 , a wavelength detection module  208 , an internal switching device module  210 , a Bit Error Rate (BER) pattern generation module  212 , a BER analyzer module  214 , an Optical Signal to Noise Ration (OSNR) module  216 , a user interface  218 , and an ITASWSS/ITASWSS interface  220  coupled together via bus  222  over which the various elements may interchange data and information. 
   The analytical engine module  202  includes a processor  224  and a memory  226 , each coupled to bus  222 . The analytical engine module  202  coordinates the execution of a test and/or test sequence. Memory  226  includes routines  228  and data/information  230 . The processor  224 , e.g., a CPU, executes the routines  228  and uses the data/information  230  in memory  226  to control the operation of the ITASWSS and implement the methods of the present invention. Operations controlled by the analytical module  202  include storing and executing testing configurations, talking to the wavelength switch  104  under test through the corresponding protocol adaptor, collecting timing data, executing correlations, and enabling presentation of data through a user interface  218 . 
   Protocol Adaptor module  204  includes a plurality of protocol adaptors, protocol adaptor  1   232 , protocol adaptor N  234 . Protocol adaptor  1   232  is coupled to switch control interface port  1   236 ; protocol adaptor N  234  is coupled to switch control interface port N  238 . Switch control interface ports  236  or  238  may be the switch control interface port  114  of ITASWSS  1   102  in  FIG. 1 . 
   Ports  236 ,  238  may be, e.g., an Ethernet port or a serial port. Protocol adaptors  232 ,  234  communicate through the backplane ports of the optical switching system under test, e.g., port  122  of wavelength switch  104  in  FIG. 1 , and instruct the wavelength switch  104  of specific configurations needed for the test in operation. The protocol adaptors  232 ,  234  translate either a command line input request or emulate a signaling and control protocol to instruct the wavelength switch  104  to make the appropriate connections. In some embodiments, the protocol adaptors  232 ,  234  are programmed in the analytical engine module  202  as a series of software modules specifically tailored to each proprietary interface of a given vendors wavelength switch  104 . 
   Wavelength generation module  206  includes a plurality of optical signal wavelength generators, optical signal wavelength generator  1   240 , optical signal wavelength generator N  242 . An optical wavelength generator,  240 ,  242 , includes a plurality of widely tunable laser supporting channels in the C band and L band, e.g., 80 to 100 channels at a 1550 nm window, as well as channels in other windows, e.g., a 1330 nm window, a 1400 nm window, a 1600 nm window. Thus optical wavelength generator  240 ,  242  provides a continuous spectrum of wavelengths in the testing range to simulate the typical wavelengths inputted into optical switch presently used and allowing for expansion into wavelengths planned to be used in the future. In some embodiments, the range of wavelengths available from wavelength generation module  206  may be subdivided between the plurality of wavelength generators  240 ,  242 . Wavelength generators  240 ,  242  are capable of modulation and variable power. The wavelength generators  240 ,  242  may be controlled by the analytical engine module  202  to modulate information onto selected wavelengths at selected times thus generating a plurality of test signals. Exemplary test signals  244 ,  246 ,  248 , and  250  are shown in  FIG. 2 . The power level of the generated test signals may also be controlled by the analytical engine module  202 . The wavelength generator module  206  is coupled to internal switching device module  210  via a plurality of optical links, e.g. optical fibers,  252 ,  254 ,  256 ,  258  through which test signals  242 ,  246 ,  248 ,  250 , respectively, are transmitted. 
   Internal switching device module  210  is coupled to the optical output interface  260  via a plurality of optical links, e.g., multimode optical fibers,  262 ,  264 . 
   Optical output interface  262  includes a plurality of optical output ports, port  1   266 , port N  268 . Optical output port  1   266  may be port  108  of  FIG. 1 , while optical output port N  268  may be port  110  of  FIG. 1 . Port  1   266  is coupled to optical link  262 , while port N  268  is coupled to optical link  264 . Internal switching device  210 , under the direction of the analytical engine module  202 , switches received input signals  242 ,  244 ,  246 ,  248  to the appropriate optical port so that routing will result in the appropriate test signals being transmitted to the appropriate ports  128 ,  130  of the wavelength switch  104  under test. In the example shown in  FIG. 2 , test signals  244  and  250  have been switched onto optical link  262 , while test signals  246  and  248  have been switched onto optical link  264 . 
   ITASWSS  200  also includes an optical input interface  270  including a plurality of optical input ports, port  1   272 , port N  274 . Optical input port  1   272  may be port  118 ′ of  FIG. 1 , while optical input port N  274  may be port  120 ′ of  FIG. 1 . Test signals received as output from the unit under test, e.g., from wavelength switch  104 , are received through optical input ports  272 ,  274 . Port  1   272  is coupled via optical link  276 , e.g., a multimode optical fiber, to internal switching device module  210 . Similarly, optical port N  274  is coupled to internal switching control device module  210  via optical link  278 . In the example of  FIG. 2 , optical link  276  conveys signals  278  and  280  to switching module  210 , while optical link  278  conveys signals  282 ,  284  to switching module  210 . 
   The internal switching device module  210  is coupled to the wavelength detection module  208  via a plurality of optical links  286 ,  288 ,  290 ,  292 . The wavelength detection module  208  includes a plurality of wavelength detectors, wavelength detector  1   294 , wavelength detector N  296 . In some embodiments, different wavelength detectors  294 ,  296  may cover detection for different ranges of wavelengths. Internal switching device module  210  under the direction of the analytical engine module  202  separates, groups, and/or directs the received test signals to the appropriate optical links  286 ,  288 ,  290 ,  292  so that the received signals may be routed to the appropriate detector  294 ,  296  at the appropriate time. In the example of  FIG. 2 , signal  284  is conveyed through optical link  286 , signal  278  is conveyed through optical link  288 , signal  282  is conveyed through optical link  290 , and signal  280  is conveyed through optical link  292 . 
   Optical signal wavelength detectors  294 ,  296  include an optical spectrum analyzer with power detection and wavelength analysis capabilities. Optical signal wavelength detectors  294 ,  296  are also capable of providing measurements on wavelength selective switch parameters such as directivity, isolation, cross-talk, power level, attenuation, etc. 
   Bit Error Rate (BER) pattern generation module  212 , under the control of the analytical engine module  202 , acts an input to wavelength generator module  206  and generates variable bit rate errors in the information being conveyed as test signals generated by wavelength generator module  206 . BER pattern generation module  212  operates at specific bit rate ranges, e.g., 0-700 Mbps, 700-2.5 Gbps, or multi-range, and is used in the generation of test signals for measuring digital signal performance. 
   BER Analyzer Module  214  receives output information from the wavelength detection module  208 . BER Analyzer module  214  operates at specific bit rate ranges, e.g., 0-700 Mbps, 700-2.5 Gbps, or multi-range, and is used in the analysis of received test signals for measuring digital signal performance. By detecting the received BER, and knowing the transmitted BER, degradation, e.g., due to the unit under test, e.g., wavelength switch  104 , can be obtained. 
   Wavelength detection module  208  also directs output signals and/or information to the OSNR module  216 . OSNR module  216  measures analog signal performance, e.g., optical signal to noise ratio. 
   User interface  218  includes a user I/O port  298  and supporting circuitry, e.g., interface drivers and receivers. User interface  218  supports interface with an operator device  106 , e.g., a graphical interface device. The user I/O port  298  may be I/O port  112  of  FIG. 1 . ITASWSS/ITASWSS interface  220  includes ITASWSS/ITASWSS port  299  and supporting circuitry, e.g., interface drivers and receivers. ITASWSS/ITASWSS interface  220  allows ITASWSS  200  to be coupled and communicate with other ITASWSSs, e.g., in a dual ITASWSS testing mode as shown in  FIG. 1 . Port  299  may be port  116  or  116 ′ of  FIG. 1 . 
     FIG. 3  is an illustration of an exemplary memory  226  that may be used in the analytical engine module  202  of exemplary ITASWSS  200  of  FIG. 2  in accordance with the present invention. Memory  226  includes routines  228  and data/information  230 . Routines  228  includes a communications module  302 , a user interface control module  304 , a protocol adaptor programming module  306 , a system testing control module  308 , a system parameter measurement module  310 , a performance measurement module  312 , an evaluation verification module  314 , a SLA detection module  316 , a higher protocol impact evaluation module  318 , a results storage module  320 , and a comparative performance module  322 . 
   Data/information  230  includes identification information  324 , protocol information  326 , test sequence/user options information  328 , current configuration information  330 , test specification limits information  332 , test results logs  334 , and current test results  336 . 
   Identification information  324  includes test equipment information  338 , e.g., manufacturer, model, S/N, control and ranging information, corresponding to wavelength generator  240 ,  242  equipment, wavelength detector  294 ,  296  equipment, BER modules  212 ,  214  equipment, and ONSR module  216  equipment that is in ITASWSS  200  and/or information pertaining to substitute equipment that may be installed in ITASWSS  200 . Optical switch information  340  includes information corresponding to a plurality of optical wavelength switches from a plurality of vendors which may be tested by the ITASWSS  200  in accordance with the present invention. Optical switch information  340  may include information defining the specific protocol, e.g., a vendor specific protocol, used for the switching control, e.g., for communications over port  122  of wavelength switch  104  of  FIG. 1 . Optical switch information  340  also includes characteristics of the optical switch&#39;s interfaces and ports, such as physical connector used, voltage levels, frequency ranges, wavelengths, power requirements, numbers of input and output optical ports, number of channels per optical port, customer advertised switching characteristic, etc. 
   Protocol information  326  includes a plurality of sets of protocol information, protocol  1  information  342 , protocol N information  344 . Each set of protocol information  342  corresponds to a particular protocol used by a wavelength switch vendor to control the vendor&#39;s wavelength switch. In some cases, vendors may supply multiple models of switches which use the same protocol. Additional sets of protocol information may be added to protocol information  326  as different vendors offer new devices or upgraded models of wavelength switches which use different control signals and/or control protocols. Test sequence/user options information  328  includes menu information that is presented to a user, e.g., over user interface  218 . Test sequence/user options information  328  includes information pertaining to predetermined sequences of tests used to characterize and/or evaluate a wavelength switch. Test sequence/user options information  328  also includes information pertaining to specific tests, e.g., a dedicated or more extensive test that may be applied to more carefully evaluate or troubleshoot one feature of the wavelength switch, e.g., cross-talk adjacent channels. 
   Current configuration information  330  includes information identifying the specific test equipment presently employed in ITASWSS  200  and the specific unit under presently under test, e.g., wavelength switch  104  from manufacturer A model B S/N  123 . Current configuration information  330  also includes information identifying the current test and/or test step in progress. Test specification limits  332  includes specification limits for various wavelength switches considered acceptable by the service provider and specification limits for various wavelength switches as advertised by the vendor of the wavelength switch. Such limits may correspond to parameters measured by the ITASWSS  200  such as those included in current test results  336 , e.g., switching time and bit error rate. 
   Current test results  336  includes system parameters  354  and performance parameters  356 . Current test results  336  is a set of test results obtained on the wavelength switch  104  under test and may include raw measurement data results and summarized data results. System parameters include  354  include switch timing parameters  358 , spectral attenuation  360 , insertion loss  362 , chromatic dispersion  364 , polarization mode dispersion  366 , polarization dependent loss  368 , optical return loss  369 , optical power range  370 , isolation  372 , directivity  374 , cross talk adjacent channels  376 , and cross talk non-adjacent channels  378 . Switch timing  358  includes switching time  384 , switching speed  386 , and full switch capacity  387 . Performance parameters  356  includes bit error rate  380  and optical signal to noise ratio  382 . 
   Test results logs  334  includes a plurality of test result logs, switch  1  result info  388  and switch N result info  390 . Each log  388 ,  390  is a storage of information after completion of a testing session with a wavelength switch  104 . Switch  1  result information  388  includes identification information  346  and test results information  348 . The identification information  346  includes information identifying the wavelength switch tested by manufacturer model, and S/N. Identification information  346  also includes information identifying the specific ITAWSS or ITASWSSs used to conduct the test and the specific test equipment used in each of the ITASWSSs. Time tag information indicating the date and time of the testing session is also included in the identification information  346 . Test results information  348  is a copy and/or a processed version of the current test results  336  obtained at the completion of the testing session. 
   Communication module  302  uses the data/information  230  in memory  226  to control signaling between the various elements of ITASWSS  200  and to control ITAWSS/ITAWSS communications. User Interface control module  304  controls operation of user interface  218  allowing a user, e.g., with a graphical interface, to configure the ITASWSS, select and command testing options from a menu, view and evaluate test results obtained, view test results in relation to specifications, request summarizations of test results, tailor the test sequence, comparatively evaluate multiple test results from one or more tested wavelength switches, e.g., corresponding to different manufacturers, to input new protocol information, and to input new wavelength switch type information. 
   Protocol adaptor programming module  306  uses information in data/information  230  such as optical switch information  340 , current configuration information  330 , and protocol information  342  to match up the specific unit under test, e.g. specific wavelength switch  104 , with the appropriate protocol and then to program one of the protocol adaptors  232 ,  234  with a specially tailored software module corresponding to the proprietary interface of the specific vendor&#39;s wavelength switch  104  to be tested. After the protocol adaptor  232 ,  234  is programmed, the analytical engine module  202  can send standard signals using its own internal protocol to issue a specific switching control command, and the protocol adaptor  232 ,  234  will convert the command to an equivalent command or commands in the switch vendor&#39;s protocol so that test instructions may be understood and executed by the vendor&#39;s wavelength switch  104 . In addition, result signaling from the wavelength switch  104  such as fault information and status information should be converted from the wavelength switch vendor&#39;s protocol to the ITASWSS system internal protocol, by the protocol adaptor  232 , 234 , so that such information may be recovered and understood by analytic engine module  202 . 
   System testing control module  308  provides overall control of the user selected testing. Operations of module  308  include controlling the wavelength generator module  206 , controlling the internal switching device module  210 , sending switching signals to the protocol adaptor module  204 , and coordinating overall timing. System parameter measurement module  310  uses information in data/information  230 , and controls the wavelength detection module  208  to obtain system parameter information  354 . System parameter measurement module  310  may perform processing of some of the data output from the wavelength detection module  208  to obtain some of the system parameters  354 . 
   Performance measurement module  312  controls operation of the BER pattern generation module  212 , BER analyzer module  214 , and OSNR module  216  to obtain performance parameters  356  such as BIT error rate  380  and optical signal to noise ratio  382  for the wavelength switch  104  under test. 
   Evaluation/verification module  314  compares a set, or partial set, of results, e.g., current test result  354 , against test specification limits  332 . For example, the results may be compared to be displayed in a graphical format, e.g., bar graphs, for a user. An obtained current testing result value such as switching time  384  may be plotted on the same graph with the specification limit acceptable to the service provider and the specification limit advertised by the switch vendor. Evaluation/verification test module  314  can generate warning indications during or after the testing to clue the user to focus on potential trouble areas for additional specialized testing. In addition evaluation/verification module  314  can generate overall evaluation reports. 
   SLA detection module  316  generates evaluation information based on a calculation of percent of error free parameters derived from the BER measurements. 
   SLA detection module  316  analyzes the impact of selected parameters on the performance of the switch, e.g., percent availability, blocking rate. Such evaluation information generated by SLA detection module  316  can be presented to the user, e.g., graphically, through the user interface  218 , output to an external higher level system, e.g. through user interface  218 , for SLA estimation in higher level protocols, e.g., Transmission Control Protocol/Internet Protocol (TCP/IP), and/or forwarded to the higher level protocol impact evaluation module  318 . 
   Higher level protocol impact evaluation module  318  uses forwarded information pertaining to the wavelength switch to evaluate the impact on the higher levels protocols that may be used on signaling traversing the wavelength switch. 
   Results storage module  320  transfers current test information  336 , and relevant information from identification information  324  and current configuration information  330  into a result test logs  334  information set, e.g., switch n result information  390 . Comparative performance module  322  allows a user to select information from two or more test result logs  388 ,  390  and obtain a comparison. In some embodiments, comparison reports and/or displays are generated automatically as part of the testing process. Such comparisons may be used to distinguish between two wavelength switch vendors in competition, to evaluate a population of wavelength switches supplied by the same vendor, to evaluate a new model switch by the same vendor, and/or to evaluate the same S/N wavelength switch for any degradation due to aging. 
     FIG. 4  is a flowchart  400  of an exemplary method of operating a wavelength switch testing system, e.g., exemplary testing system  100 , in accordance with the present invention. Operation starts at step  402  and proceeds to step  404 , where the test system is initialized, e.g., the ITASWSS(s)  102 ,  102 ′ and user interface device  106  are powered on and communications are established. Operation proceeds to step  406 , where the test system is operated to prompt the user with options: test a wavelength switch, update memory for a new protocol, update memory for a new switch type, obtain a comparison report, or obtain a higher level protocol impact evaluation report. 
   The user chooses an option and inputs a user selection  408  via user interface device  106 . Then, in step  410 , ITASWSS  102  receives user selection  408  and processes the user selection. If the selection is to test a wavelength switch  412 , then operation proceeds to step  422 . If the selection is to update memory for a new protocol  414 , then operation proceeds via connecting node B  415  to step  502 . If the selection is to update memory for a new switch type  416 , then operation proceeds via connecting node C  417  to step  508 . If the selection is to obtain a comparison report  418 , then operation proceeds via connecting node D  419  to step  514 . If the selection is to obtain a higher level protocol impact evaluation report  420 , then operation proceeds via connecting node E  421  to step  520 . 
   Assuming that a wavelength switch is to be tested, operation proceeds to step  422 , where the test system prompts the user for wavelength switch identification information, e.g., vendor, P/N, model, S/N, software release version, etc. The user inputs switch ID information  424  into the user interface device  106  and in step  426  the testing system processes the user input  424  and checks to see if the switch type is currently supported by the testing system, For example, ITASWSS  102  can check in its memory  226  to see if there is a corresponding entry matching the vendor, P/N, model number, and software release version. Then in step  428  the operation is directed based upon the result of the check. If the switch is currently supported, then operation proceeds from step  428  to step  430  where the ITASWSS testing system is configured for the specific type of wavelength switch  104  to be tested. Step  430  includes sub-step  434  in which ITASWSS  102  user interface control module  304  assigns an appropriate protocol adaptor  232 ,  234  to support communications with the wavelength switch  104 . Different protocol adaptors  232 ,  234  may support may support the loading of different protocol conversion information, and different protocol adaptors  232 ,  234  may have different physical switch control interface ports, e.g., a serial communications port vs a parallel communications port. Step  430  also includes sub-step  436 , where the ITASWSS&#39;s  102  protocol adaptor programming module  306  selects the appropriate protocol information  342 ,  344 , matching the protocol used by the wavelength switch  104  to be tested, and programs the selected protocol adaptor, e.g., protocol adaptor  1   232 . However, if the wavelength switch  104  is not currently supported, then operation proceeds from step  428  to step  432 , where the ITASWSS  102  notifies the user that the wavelength switch  104  is not currently supported and that ITASWSS memory should be updated for a new switch type and/or a new protocol. From step  432  operation proceeds via connecting node H  405  back to step  406 , where the user is prompted with input options. 
   From step  430 , operation proceeds via connecting node A  431  to step  438 , where the ITASWSS  102  is operated to instruct the user to connect specific ITASWSS optical interface output ports  108 ,  110 , e.g., on a first ITASWSS  102 , to other specific ITAWSS optical input interface ports  118 ′,  120 ′, e.g., on a second ITASWSS  102 ′, and the user performs the connections. Then, in step  440 , the ITASWSS  102  is operated to generate test signals, and ITASWSS  102 ′ is operated to detect test signals and obtain baseline data of the testing system without a wavelength switch. The information obtained in step  440  may be used to calibrate the system, so that observed changes in test signals due to the wavelength switch  104  may be isolated from observed changes in test signals due to the testing system itself. 
   Next, in step  442 , the ITASWSS  102  is operated to instruct the user to install the wavelength switch  104  to be tested specifying: switch control port selection and connections, and optical input and output port selections and connections. In step  444 , the user connects the wavelength switch  104  to be tested to the testing system as instructed. Next, in step  446 , the ITASWSS  102  is operated to prompt the user to select the type of test to be performed: a standard automated test sequence or a selected test. User test type selection input  448  is received and processed by the ITASWSS  102  in step  450 . If the user selection=standard automated test sequence ( 452 ) operation proceeds via connecting node F  453  to step  456 ; however, if the user selection=a selected test ( 454 ) then operation proceeds via connecting node G  455  to step  476 . 
   If operation proceeds to step  456 , then the ITASWSS is operated to perform the automated test sequence. 
   Step  456  includes sub-steps  458 ,  460 ,  462 ,  464 ,  466 ,  468 , and  470 . In sub-step  458  the ITASWSS  102  is operated under the direction of the system testing control module  308  to follow a predefined test profile and coordinate/synchronize operations internally, with wavelength switch  104 , and with second ITASWSS  102 ′. In sub-step  460 , the analytic engine module  202  in ITASWSS  102  sends switching control command signals to the protocol adaptor in use, e.g., protocol adaptor  232 . In sub-step  462 , the protocol adaptor is operated to convert received command signals from the protocol used by the analytic engine module  202  to the protocol used by the wavelength switch under test. Then the converted signals are forwarded to the wavelength switch  104 . In sub-step  464 , ITASWSS  102  is operated to generate test signals, e.g., using wavelength generator module  206  and BER pattern generator module  212 , and to direct those test signals, e.g., by controlling internal switching device module  210 , to optical input port(s) of the wavelength switch. In sub-step  466 , ITASWSS  102 ′ is operated to receive test signals from the optical output ports of the wavelength switch  104 , and direct those test signal, e.g., by controlling its internal switching device module  210 , to its wavelength detectors  294 ,  296 . In sub-step  468 , the ITASWSSs  102 ,  102 ′ are operated using their system parameter measurement modules  310  to measure, process, analyze and/or evaluate received test signals to determine system parameters for the wavelength switch, e.g., switching time, spectral attenuation, etc. In sub-step  470 , the ITASWSSs  102 ,  102 ′ are operated using performance measurement modules  312  to control the BER analyzer module  214  and OSNR module  216  in ITASWSS  102 ′ and to process, analyze and/or evaluate received test signals to determine performance parameters for the wavelength switch, e.g., bit error rate and OSNR. 
   Operation proceeds from step  456  to step  472 . In step  472 , ITASWSS  102  is operated so that its evaluation verification module  314  generates an evaluation/verification report on the wavelength switch  104  under test and outputs the report to the user, e.g., in a graphical format. The evaluation verification module  314  compares test specification limits  332  to current test results  336 . Then in step  474 , the ITASWSS  102  stores current test results  336  and identification information, e.g., identification information included in current configuration information  330  in a test log, corresponding to a testing session, in test results log  334 . Operation proceeds from step  474  via connecting node H  405  back to step  406  to again prompt the user with available options. 
   Returning to step  450 , if the if the user selection=a selected test ( 454 ) then operation proceeds via connecting node G  455  to step  476 . In step  476 , the user is prompted with a menu of options, e.g., a list of available individual tests, e.g., an optical power range test, a bit error rate test, etc. Next, in step  480  user test selection  478  is received and processed by ITASWSS  102 . In addition, in step  480  there may be additional information exchanges between the user and ITASWSS  102  to define and implement any specific test variables to be specially controlled, e.g., focus testing on a specific frequency range, a specific optical port, etc. Next, in step  482 , the ITASWSS testing system is operated to perform the selected test. Step  482  includes sub-steps  484 ,  486 ,  488 ,  490 ,  492 ,  494 , and  496 . In sub-step  484 , ITASWSS  102  is operated to follow a test profile corresponding to the selected test and to coordinate/synchronize operations, e.g., with internal components, with ITASWSS  1021 , and with wavelength switch  104 . In sub-step  486 , analytic engine module  202  of ITASWSS  1021  is operated to send switching control command signals to a protocol adaptor, e.g., protocol adaptor  232 . In sub-step  488 , the protocol adaptor is operated to convert command signals from the protocol used internally for signaling within the ITASWSS  102  to the protocol used to by the wavelength switch  104  under test and to forward those signals to the wavelength switch  104 . 
   In sub-step  490 , ITASWSS  102  is operated to generate test signals, e.g., using its wavelength generator module  206  and/or BER pattern generator module  212 , and to direct those test signals, e.g., by controlling its internal switching device module  210 , to optical input port(s) of the wavelength switch. In sub-step  492 , ITASWSS  102 ′ is operated to receive test signals from the optical output ports of the wavelength switch  104 , and direct those test signal, e.g., by controlling its internal switching device module  210 , to its wavelength detectors  294 ,  296 . In sub-step  494 , the ITASWSSs  102 ,  102 ′ are operated using system parameter measurement modules  310  to measure, process, analyze and/or evaluate received test signals to determine system parameters for the wavelength switch, e.g., switching time, spectral attenuation, etc, as required by the specific test being performed. In sub-step  496 , the ITASWSSs  102 ,  102 ′ are operated using performance measurement modules  310  to control the BER analyzer module  214  and OSNR module  216  in ITASWSS  102 ′ and to process, analyze and/or evaluate received test signals to determine performance parameters for the wavelength switch, e.g., bit error rate and OSNR, as required by the specific test being performed. 
   Operation proceeds from step  482  to step  498 . In step  498 , ITASWSS  102  is operated so that its evaluation verification module  314  generates an evaluation/verification report on the wavelength switch  104  under test and outputs the report to the user, e.g., in a graphical format. The evaluation verification module  314  compares test specification limits  332  to current test results  336 . Then in step  500 , the ITASWSS  102  stores current test results  336  and identification information, e.g., identification information included in current configuration information  330  in a test log, corresponding to a testing session, in test results log  334 . Operation proceeds from step  500  via connecting node H  405  back to step  406  to again prompt the user with available options. 
   Returning to step  410 , if the user selection  408  is a request to update memory for a new protocol ( 414 ), then operation proceeds via connecting node B  415  to step  502 . In step  502 , the user is prompted to enter new protocol information, e.g., protocol identification information and information used by the protocol programming module. The protocol identification information may also include information cross referencing the protocol to various vendor/models of wavelength switches. In some embodiments, the information includes developed software modules, e.g., conversion modules, for the new protocol, which can be transferred into the ITASWSS memory  324  as part of a protocol information set of information, e.g., protocol N information  344 . In such an embodiment, the stored software module may subsequently be transferred, e.g., by the protocol adaptor programming module  306  into a protocol adaptor, e.g., protocol adaptor  232 , when required by testing. Operation proceeds from step  502  to step  506 . In step  506 , the ITASWSS  102  is operated to receive and store the new protocol information from the user  504  in its memory  226 . New protocol information received by ITASWSS  102  is transferred to ITASWSS  102 ′, where the information is also stored. Operation proceeds from step  506  via connecting node H  405  back to step  406  to again prompt the user with available options. 
   Returning to step  410 , if the user selection  408  is a request to update memory for a new wavelength switch type ( 416 ), then operation proceeds via connecting node C  417  to step  508 . In step  508 , the user is prompted to enter new switch information, e.g., identification information, protocol used, vendor advertised limits, number/type of ports, etc. Next, in step  512 , the ITASWSS  102  is operated to receive and store the new wavelength switch type information from the user  510  in its memory  226 . Updated wavelength switch information received by ITASWSS  102  is transferred to ITASWSS  102 ′, where the information is also stored. Operation proceeds from step  512  via connecting node H  405  back to step  406  to again prompt the user with available options. 
   Returning to step  410 , if the user selection  408  is a request to obtain a comparison report ( 418 ), then operation proceeds via connecting node D  419  to step  514 . In step  514 , the user is prompted to select test log records  338 ,  390 , parameters, and/or wavelength switches, e.g., by S/N, model, vendor, etc., to be compared. Next, in step  518 , the ITASWSS  102  is operated to receive comparison selection information from the user  516 , generate a comparison report under the direction of comparison performance module  322 , an forward a comparison report to the user, e.g., in a graphical format. Operation proceeds from step  518  via connecting node H  405  back to step  406  to again prompt the user with available options. 
   Returning to step  410 , if the user selection  408  is a request to obtain a higher level protocol impact evaluation report ( 418 ), then operation proceeds via connecting node E  421  to step  520 . In step  520 , the user is prompted to select a test result log(s) to be analyzed and to identify higher level protocol(s) to be evaluated. The higher levels protocol(s) are protocols, e.g., Transmission Control Protocol/Internet Protocol (TCP/IP), that may be used by the service provider&#39;s network on information that is conveyed through a deployed wavelength switch. Next, in step  524 , the ITASWSS  102  is operated to receive test result log selection and higher level protocol information from the user  522 , perform a higher level protocol evaluation under the direction of module  318 , and forward an impact report to the user. Operation proceeds from step  524  via connecting node H  405  back to step  406  to again prompt the user with available options.