Abstract:
A wavelength tunable device for use in a wavelength division multiplexing (WDM) system comprising a display device for displaying at least one operating wavelength of the wavelength tunable device. The display device is electrically coupled to a control unit in the wavelength tunable device so as to display the tuned wavelength in real time. The wavelength tunable device may be, in exemplary embodiments, an optical transponder, wavelength division demultiplexer, or wavelength division multiplexer. In embodiments where the optical equipment has a plurality of tunable ports, the display device is adapted to display the operating wavelength of each tunable port.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is a continuation of U.S. patent application Ser. No. 12/460,331, filed Jul. 17, 2009, which is a continuation U.S. patent application Ser. No. 11/322,069, filed Dec. 29, 2005, issued on Aug. 11, 2009 as U.S. Pat. No. 7,574,136, the disclosures of which are incorporated by reference herein in their entirety. 
    
    
     BACKGROUND 
     The present invention relates generally to optical networking, and more particularly, to a device for displaying the operating wavelength of wavelength tunable equipment in real time on the equipment. 
     In a traditional wavelength division multiplexing (WDM) system having transponders operating at a fixed wavelength, such wavelength is set during the manufacturing process. Within the WDM system, each transponder operates at a unique wavelength and, in terms of hardware and software, differs from other transponders operating at diverse wavelengths. For operational and maintenance purposes, the wavelength is usually printed or marked on the faceplate of each transponder. As wavelength tunable technologies are maturing, tunable transponders and other optical devices are starting to be deployed in WDM optical networks. In this regard, the wavelength of these transponders and other devices can be dynamically tuned as needed during operation. Within a WDM system, tunable transponders are physically the same, irrespective of the operating wavelength. Although each has the same hardware and software, the only difference between these transponders is that each is tuned to a unique wavelength during operation. The particular wavelength associated with each transponder can only be read from the craft interface terminal (CIT) and/or element management system (EMS), but cannot be readily identified directly from the equipment since all the transponders are structurally identical and look the same on the equipment. Consequently, operational personnel cannot ascertain the wavelength of each transponder by simply looking at the transponder, or without access to a CIT and/or EMS. For troubleshooting and other maintenance activities, it is a quite difficult and time-consuming task for operational personnel to identify a specific transponder among many such units. Moreover, there is a potential risk for traffic interruption if the personnel perform maintenance on the wrong transponder. On the other hand, it is undesirable to label (via printing or marking) the wavelength on each piece of equipment, particularly in the case of tunable WDM equipment, where the wavelength of a unit can be dynamically tuned during operation. It is not cost effective and a waste of resources to re-label the wavelength on such equipment every time the operating wavelength is changed to suit a particular application. 
     SUMMARY 
     In accordance with an aspect of the disclosure, it is an object thereof to display the operating wavelength of tunable optical equipment in a WDM optical network in real time. 
     It is a further object of the disclosure to electronically display the operating wavelength of a tunable optical transponder for use in a WDM optical network in real time. 
     It is still another object of the disclosure to provide maintenance personnel with a means of identifying the operating wavelength of tunable optical equipment in a WDM optical network without the need to access a CIT or EMS to obtain selected wavelength information. 
     It is yet another object of the disclosure to provide a liquid crystal display (LCD), light emitting diode (LED) or like device, on the faceplate of tunable optical equipment in a WDM optical network, to enable more efficient maintenance and prevent a risk of traffic interruption caused by failure to identify the equipment properly. 
     In accordance with an aspect of the disclosure, a wavelength tunable device for use in a wavelength division multiplexing (WDM) system comprises a display device for displaying at least one operating wavelength of the wavelength tunable device. The display device is electrically coupled to a control unit disposed in or otherwise associated with the wavelength tunable device so as to display the tuned wavelength in real time. In an exemplary embodiment, the wavelength tunable device is an optical transponder, which comprises a line transmitter and a line receiver, where the line transmitter and line receiver may each be dynamically tuned to a selected wavelength. 
     In another embodiment, the wavelength tunable device is a wavelength division demultiplexer constructed and arranged for receiving an input multiplexed optical signal and comprising a plurality of tunable ports that output optical signals at specific wavelengths, where the display device is coupled to a control unit and adapted to display the wavelength of each of the plurality of tunable ports. Similarly, the wavelength tunable device can be a wavelength division multiplexer comprising a plurality of tunable ports for receiving individual optical signals at specific wavelengths, where the wavelength division multiplexer constructed and arranged for outputting a multiplexed optical signal, and the display device is coupled to a control unit and adapted to display the wavelength of each of the plurality of tunable ports. 
     These and other advantages of the disclosure will be apparent to those of ordinary skill in the art by reference to the following detailed description and the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic of an exemplary optical transponder utilized in WDM optical networking systems; 
         FIG. 2  is a schematic of an exemplary bi-directional point-to-point WDM optical transmission system; 
         FIG. 3  is a schematic of an optical transponder in accordance with an aspect of the disclosure; 
         FIG. 4  is a schematic of a wavelength division demultiplexer in accordance with an aspect of the disclosure; and 
         FIG. 5  is a schematic of a wavelength division multiplexer in accordance with an aspect of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a schematic diagram of a typical optical transponder  100  comprising a client receiver  102 , client transmitter  104 , line receiver  106 , line transmitter  108  and processing devices  110  and  112 . An optical signal  114  from equipment on the optical network (not shown) is received by the client receiver  102 , and then converted by an optical/electrical (O/E) converter to an electrical signal. The converted signal is applied to processor  110  which implements mapping/de-mapping, monitor overheads and the like. Line transmitter  108  utilizes an electrical/optical (E/O) converter to convert the processed electrical signal to an optical signal  116  at a specific wavelength. In a similar fashion, an optical signal  118  at a specific wavelength is received by line receiver  106 , and then converted to an electrical signal by an O/E converter. The converted signal is applied to processor  112 , and subsequently applied to client transmitter  104  which utilizes an E/O converter to convert the electrical signal to a client optical signal  120  for transmission to other equipment on the network. The wavelength of the line transmitter  108  can be specifically tuned as required during operation by utilizing tunable lasers. This type of transponder is therefore commonly referred to as a tunable transponder. Line receiver  106  is typically a broadband receiver, which is constructed and arranged to receive an optical signal at any wavelength within an allowable range. The wavelength of the incoming signal  118  to line receiver  106  is usually fixed by a wavelength sensitive demultiplexer. However, by utilizing a tunable filter or wavelength selective switch, the line receiver  106  can also be dynamically tuned to select an optical signal at a specific wavelength within the multiplexed incoming signal. 
     Since a typical WDM system can accommodate a large amount of channels (i.e., from several to more than a hundred), each channel requires one pair of transponders that operate at a specific wavelength. Referring now to  FIG. 2 , there is depicted a schematic of a simplified WDM system that transmits optical signals between two sites identified as “Office A” and “Office B.” In Office A, a first transponder  200   1  outputs a line optical signal at a specific wavelength (W1) through a fiber jumper  202   1  to a wavelength multiplexer (WMUX)  204 . Similarly, a plurality of additional transponders  200   2  . . .  200   n  in Office A output respective optical signals over fiber jumpers  202   2  . . .  202   n  at unique wavelengths W1 . . . Wn to the WMUX  204 . The WMUX  204  then multiplexes all the line optical signals at wavelengths W1 . . . Wn generated by transponders  200   1  . . .  200   n . The multiplexed optical signal  206  is amplified by an optical amplifier  208  and then injected into a transmission optical fiber  210 . After transmission over some distance, the optical signal, which is weakened due to fiber transmission losses, is amplified by an another optical amplifier  212  and possibly additional optical amplifiers, the last of which is depicted in the receiving Office B at  214 . In Office B, the multiplexed optical signal is received and then separated into a plurality of corresponding optical signals, each having its original unique wavelength via a wavelength demultiplexer (WDMUX)  216 . The demultiplexed optical signal at wavelength W1 is connected via a fiber jumper  218   1  to the receiver of transponder  220   1 . All other demultiplexed optical signals at wavelengths W 2  . . . W n  are also connected via fiber jumpers  218   2  . . .  218   n  to additional wavelength-specific transponders  220   2  . . .  220   n . 
     For transmissions in the opposite direction from Office B to Office A, the first transponder  220   1  outputs a line optical signal at a specific wavelength (W1) through a fiber jumper  222   1  to a WMUX  224 . Similarly, the additional transponders  220   2  . . .  220   n  in Office B output respective optical signals over fiber jumpers  222   2  . . .  222   n  at unique wavelengths W1 . . . Wn to the WMUX  224 . The WMUX  224  then multiplexes all the line optical signals at wavelengths W1 . . . Wn generated by transponders  220   1  . . .  220   n . The multiplexed optical signal  226  is amplified by an optical amplifier  228 , injected into a transmission optical fiber, re-amplified by illustrative optical amplifiers  230  and  232 , and received by DEMUX  234  in Office A as described in the foregoing. The demultiplexed optical signal at wavelengths W1 . . . Wn is then input to the respective transponders  200   1  . . .  200   n  via fiber jumpers  236   1  . . .  236   n . 
     Referring now to  FIG. 3 , there is depicted an optical transponder  300  in accordance with an aspect of the disclosure, which enables real time display of the tuned wavelength of the line transmitter and line receiver. The optical transponder  300  comprises a client receiver  302 , client transmitter  304 , line receiver  306 , line transmitter  308  and processing devices  310  and  312  as described above and shown in  FIG. 1 . An optical signal  314  from equipment on the optical network is received by the client receiver  302 , and then converted by an optical/electrical (O/E) converter to an electrical signal. The converted signal is applied to processor  310 . Line transmitter  308  utilizes an electrical/optical (E/O) converter to convert the processed electrical signal to an optical signal  316  at a specific wavelength. In a similar fashion, an optical signal  318  at a specific wavelength is received by line receiver  306 , and then converted to an electrical signal by an O/E converter. The converted signal is applied to processor  312 , and subsequently applied to client transmitter  304  which utilizes an E/O converter to convert the electrical signal to a client optical signal  320  for transmission to other equipment on the network. The wavelength of the line transmitter  308  can be specifically tuned as required during operation by utilizing tunable lasers. Line receiver  306  is constructed and arranged to receive an optical signal at any wavelength within an allowable range. The wavelength of the incoming signal  318  to line receiver  306  can also be dynamically tuned to select an optical signal at a specific wavelength within the multiplexed incoming signal using a tunable filter or wavelength selective switch. A display device  322  is coupled to a control unit  328  which communicates with the line transmitter  308 , processor  310 , client transmitter  302 , line receiver  306 , processor  312  and client transmitter  304  via a bus  324 . The control unit  328  is constructed and arranged for controlling all aspects of transponder operation as will be appreciated by those skilled in the art and may be disposed either within the housing of the  333  of the transponder  300 , or at another location. The display device may be a liquid crystal display (LCD), light emitting diode (LED) or other suitable implementation for displaying the tuned wavelengths of the line receiver  306  and line transmitter  308 . The display device  322  can be mounted on a faceplate  330  on the housing  333  of the transponder  300 . The display device  322  can be constructed and arranged to display wavelength, frequency, channel number, or any other identification number corresponding to the tuned operating wavelength of the line transmitter or receiver. The display device  322  may be provided with selectable modes to alternatively display the wavelengths for the line transmitter  308  and line receiver  306 . 
     In accordance with another aspect of the disclosure,  FIG. 4  depicts a WDMUX  400  having an input port  409  coupled to an input multiplexed optical signal  401  and comprising a plurality of tunable ports  402   1 ,  402   2 , . . .  402   n  for outputting individual optical signals  403   1 ,  403   2 , . . .  403   n  on specified wavelengths. As shown in the drawing, the arrows corresponding to signals  401  and  403  represent optical signals. Each tunable port  402   1 ,  402   2 , . . .  402   n  communicates via a bus  404  with a control unit  405  as is known in the art. The bus  404  represents an electrical connection between the control unit  405 , the individual tunable ports  402   1 ,  402   2 , . . .  402   n  and input port  409 . The control unit  405  may be disposed within the WDMUX housing  407 , or externally at another location. A display device  406  is operably coupled to the control unit  405  via bus  404  to display the frequencies of tunable ports  402   1 ,  402   2 , . . .  402   n , and may comprise an LCD, LED or equivalent device as described above. The display device  406  may be mounted on the WDMUX housing  407  on a faceplate  408  to enable easy identification by personnel. The display device  406  may be provided with selectable modes to display the individual wavelengths respectively selected for each tunable port  402   1 ,  402   2 , . . .  402   n . 
       FIG. 5  depicts a WMUX  500  comprising a plurality of tunable ports  502   1 ,  502   2 , . . .  502   n  for receiving individual optical signals  501   1 ,  501   2 , . . .  501   n  on specified wavelengths and outputting a multiplexed optical signal  503  through output port  509 . Each tunable port  502   1 ,  502   2 , . . .  502   n  electrically communicates via a bus  504  with a control unit  505  in a manner similar to that described above with respect to WDMUX  400 . The control unit  405  may be disposed within the WMUX housing  507 , or externally at another location. A display device  506  is operably coupled to the control unit  505  to display the frequencies of tunable ports  502   1 ,  502   2 , . . .  502   n , and may comprise an LCD, LED or equivalent device as described above. The display devices  506  may be mounted on the WMUX housing  507  of the WMUX  500  on a faceplate  508  in a manner similar to the embodiment described above and illustrated in  FIG. 4 . 
     The present disclosure has been shown and described in what are considered to be the most practical and preferred embodiments. It is anticipated, however, that departures may be made therefrom and that obvious modifications will be implemented by those skilled in the art. It will be appreciated that those skilled in the art will be able to devise numerous arrangements and variations which, although not explicitly shown or described herein, embody the principles of the invention and are within their spirit and scope.