Abstract:
An all optical switching system which is optically switched, from the signal channel all the way to a router. Errors in the routers are detected, and indications of those errors are sent back to the optical switch. The optical switch uses a system which picks off a piece of the signal to use the control signal to control the switching.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims priority from provisional application No. 60/245,818 filed Nov. 3, 2000 and provisional application No. 60/246,683 filed Nov. 7, 2000. 

   BACKGROUND 
   This application relates to routing of optical signals in communication systems. 
   Routing of signals, and specifically optical signals, allows the signals to be properly sent from an origin to a destination. Because of the importance of reliability during such communication, many such systems include multiple levels of backup. This may be especially true in high-end routers, which may require double layers of redundancy. This redundancy, may, in turn, increase significantly the cost of such a router. 
   SUMMARY 
   The present application teaches a traffic restoration and management system which may provide redundancy in the system, in a less expensive way. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other aspects will now be described in detail with reference to the accompanying drawings, wherein: 
       FIG. 1  shows a block diagram of the basic electronic system; 
       FIG. 2  shows how a similar system can be carried out using an optical system with an optical tone, and that may return information about the router; 
       FIG. 3  shows further details on the optical switch and how it processes the optical tones; and 
       FIG. 4  shows a 100 percent redundant optical system. 
   

   DETAILED DESCRIPTION 
   A first embodiment is shown in  FIG. 1 . The  FIG. 1  embodiment may represent a building block of the basic system. A number of signals, here  12  optical signals, are input as  100 . The optical signals are each input to optical receivers, such as the receiver shown as  102 . These receivers receive the optical signal, and convert the optical signal into the electrical domain. Since there are twelve such signals, there may be twelve such receivers shown as  102  . . .  110 . The output signal  115  is an electrical signal corresponding to the respective optical input signal. The twelve electrical signals  115  . . .  120  are connected to a switching matrix  125  which may be a multiplexer, for example. The switching matrix  125  receives twelve inputs on its left side, and has 16 outputs on its right side. Notably, the switching matrix  125  has the capability of switching any of the input signals to any output signal location. Each of the  16  outputs is connected to a router. Conventional routers may handle four inputs, as shown. Therefore, each router  130  . . .  135  is shown receiving four inputs. There may be four basic routers to carry out the operations for switching for all of the  16  inputs. Each of the lines  140  between the switching matrix  125  and the router  130  carries signals to the router, but also carries control information from the router. The control information shown as  142  may include various kinds of information including the so-called K 1 , K 2  bits. 
   The K 1 , K 2  bits may inform the multiplexer switch  125  that there is a failure in the router  130 , e.g. in a specified channel of the router. However, since there are four extra channels on the right side of the multiplexer  125 , the multiplexer  125  may then switch the incoming channels to one or more of the redundancy channels. So long as not more than four channels are indicated as failed by the K 1 , K 2  bits, the redundancy will fully handle this problem. 
   The system shown in  FIG. 1  may be highly advantageous, since it may reroute any input signal to the other outputs. Moreover, because of the high-speed operation, this rerouting may occur within a short time, e.g., 50 milliseconds or so, to achieve a high speed operation. 
   However, a disadvantage of this system is that this requires complex switching units within the optical switch  125 . For example, any input such as  115  may be required to switch to any of the different outputs. This may require a very complex electrical switching network. Moreover, individual transceivers may be required which may also increase the cost of the system. The present system recognizes that this solution may be an extremely expensive solution. 
   A second embodiment is shown in  FIG. 2 . This setting embodiment carries out a similar functionality using an all optical network. 
   Optical input signals  200  are connected to an optical switch  205  which may be an optical switch of the type capable of connecting any input signal to any output signal. Since the system is all optical, it can operate without the transceivers that are necessary in the first embodiment. The output signals  210  are connected to the routers shown as  215 , with again blocks of four signals being connected to each router. An existing 16 by 16 switch is shown as being used as the switch  205 . This switch has the capability to send any of the 16 inputs to any of its outputs. However, it may be possible to use different sized switches. For example, 2, 8×8 switches may be used instead, which will allow less switching redundancy, since each one input  200  will only be switchable to one of eight different outputs  210 . An important part of this system is that, the transceivers  102 , 112  shown in  FIG. 1  are no longer necessary since the system is all optical. This may prove to be a significant cost savings. 
   However, in the system shown in  FIG. 2 , it may still be necessary for the routers  215  to provide information back to the switch  205 . Otherwise, the switch  205  will not be able to determine error information in the routers  215 . A signaling system may be used in the optical domain to carry out this operation. The signaling may occur over a line  202  or alternatively maybe the standard SONET/SDA signaling. 
   A first embodiment of the signaling system is shown in  FIG. 3 . In this system, the routers such as  215  place an optical signal shown as  300  on their optical line. The optical signal travels back towards the switch. The line  300  is monitored by an element  310  which may obtain a sample of the optical signal, the sample may represent 5 to 10 percent of the optical power in the line  300 . The sample  315  is coupled to an optical to electrical converter  320 , which converts the signal to an electrical signal  325 . The electrical signal  325  is then framed by a framer  330  and output. The output  335  represents similar information to that in the K 1 , K 2  bits and is coupled to the control circuitry  340  within the optical switch  205 . In this way, each router input and output may receive optical switch information. 
   A second embodiment defines the failure information using an optical tone system. In this embodiment, a serial bit sequence may be added to the optical signal  305  traveling to the router  215 . The signal may be amplitude modulated over the digital signal; e.g. as a 5 percent amplitude variation. The signal may be a specific tone signal, on the order of 2 MHz, with a specific tone frequency assigned to each wavelength. The signal may represent the information in the K 1 , K 2  bits. For example, these serial bits sequence may be defined as a frame of 10 consecutive bytes, including two framing bytes. After transmitting and receiving the frame, the next frame may be transmitted and received. The framing bytes delineate the frame, within which is contained the information. 
   The outgoing transmitted signal includes a tone on the order of 2 MHz, but each specific tone frequency represents a specific wavelength among the channels. The system can therefore extract the tone in the presence of multiple signals, and extract amplitude modulation information that is superimposed on the tones. The system may then process the messages per application. Since each wavelength has a slightly different tone modulation frequency, when the tone is detected, the wavelength is correspondingly detected. Another embodiment, shown in  FIG. 4 , may provide an optional redundancy block in the optical switch. In this embodiment, two different optical switches  500 , 505  each receive the operation signals, and provide their outputs to the redundancy block  510 . An error or fault in either optical switch  500 , 505  will still be corrected by the redundancy. 
   Other embodiments are possible based on the disclosed embodiment.