Abstract:
The rapid switching of optical fiber communication between one or two working optical amplifiers and one protect optical amplifier is accomplished using fast optical fiber switching and alarm detection circuits that protects the loss of communication due to amplifier failure.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention basically incorporates the casement of optical 1×2 switches along with electronic control and power circuitry to re-direct the optical signal to an protection fiber optic amplifier should one of the working fiber optic amplifiers fail. 
       BACKGROUND OF THE INVENTION 
       [0002]    An optical amplifier is a device that amplifies an optical signal without needing to convert the optical energy into electrical energy and then back again. The optical amplifier is usually placed in locations along a fiber route where there is a risk of signal degradation between the transmitting and receiving stations. 
         [0003]    In general, the number of fibers needed for bi-directional communication is two. Thus, when optical amplifiers are utilized at remote locations, they are combined in pairs to amplify the optical signal in both directions. As they are located in remote areas of the fiber network, it may take a technical crew several hours, or even days, to restore communication traffic should one of the optical amplifiers fail. Therefore, the purpose of this invention is to provide a protective measure should one of these optical amplifiers fail. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]    Examples of the present invention are illustrated in the accompanying drawings. The accompanying drawings, however, do not limit the scope of the present invention. Similar references in the drawings indicate similar elements. The protection switch is shown enclosed with a dotted line. A triangle represents an optical amplifier. A rectangle represents the 1×2 optical switch. 
           [0005]      FIG. 1  is a fiber path block diagram that shows the protection switch, 1×2 switch setting, in normal operation, with none of the working amplifiers failed. 
           [0006]      FIG. 2  is a fiber path block diagram that shows the protection switch, 1×2 switch setting, should the eastbound working amplifier fail ( 106 ). Eastbound means the optical signal direction in the fiber is left to right in this diagram. 
           [0007]      FIG. 3  is a fiber path block diagram that shows the protection switch, 1×2 switch setting, should the westbound working amplifier fail ( 107 ). Westbound means the optical signal direction in the fiber is right to left in this diagram. 
           [0008]      FIG. 4  is a block diagram of the controls that operate the protection switch. 
           [0009]      FIG. 5  is a table that shows the orientation of the optical switches in the protection switch in the four different orientations that the protection switch can be in. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0010]    The protection switch and the protective optical amplifier will remain in stand-by mode until one of the optical amplifiers generates a failure alarm to one of the input alarm termination points of the switch. Depending on which working optical amplifier fails; the switch controller will close the appropriate 1×2 optical switches components to re-direct the input optical signal to the protective optical amplifier. 
         [0011]    The protection switch,  101  (enclosed by the dotted line FIGS.  1 , 2  and  3 ) has two main inputs, an eastbound input  102 , and a westbound input,  103 . It also has two main outputs, and eastbound output  105 , and a westbound output  104 .  101  is connected to three optical amplifiers, a working eastbound amp,  106 , a working westbound amp,  107 , and a protection amp,  108 . These are connected to the main inputs and outputs by six 1×2 switches,  109 ,  110 ,  111 ,  112 ,  113 , and  114 . All those switches are functioning in normal mode, indicated by “N”. 
         [0012]    When in normal mode ( FIG. 1 ), eastbound optical fiber signals at  102  go into the protection switch. There  114  passes that signal on to  106  where it is amplified, then it goes to  109  and out at  105 . Then westbound optical signals at  103  go into the protection switch. There  110  passes that signal on to  107  where it is amplified, then it goes to  113  and out at  104 . No optical signals make it to  108 . 
         [0013]    When the protection switch  101  is configured to protect eastbound amplifier  106  or if  106  fails ( FIG. 2 ), the signal coming in from  102  is diverted by switch  114  to switch  111  which are in switch mode, indicated by a “S”, and sends the signal into amplifier  108 . After amplification switch  112  sends the signal to switch  109 , also in switch mode indicated by a “S”, and out  105 . 
         [0014]    When the protection switch  101  is configured to protect westbound amplifier  107  or if  107  fails ( FIG. 3 ), the signal coming in from  103  is diverted by switch  110 , in switch mode indicated by a “S”, to switch  111 , which is in normal mode indicated by a “N”, which sends the signal into amplifier  108 . After amplification switch  112 , again operating in normal mode, sends the signal to switch  113 , operating in switch mode, and out  104 . 
         [0015]    The method of changing the protection switch to the different configurations laid out in  FIG. 1 ,  FIG. 2 , and  FIG. 3 , is done by electronic control circuit  404 ,  FIG. 4 . It is connected to three amplifiers by electrical alarm signal connection represented by  401 ,  402 , and  403 . When one of the working optical amplifiers fails, it generates an electrical alarm which is sent to  404  by connection  401  or  402  or  403  and  404  identifies which amplifier initiated the alarm and controls the appropriate 1×2 optical switches using electrical connection to the 1×2 switches  109 ,  110 ,  111 ,  112 ,  113 , and  114  which are shown in more detail in  FIGS. 1 ,  2  and  3 .  404  also sends electrical alarm signals through  405  and  406  to any other external monitoring equipment that an amplifier has failed. 
         [0016]    If there is a case where protection optical amplifier  108  fails,  404  will send out an alarm to  405  as well and lock the switch from changing communication over to the failed protection amplifier. If the protection switch loses power from one of its dual power feeds,  404  will send out an alarm to  406 . 
         [0017]    Once the protection switch moves communications to the protection amplifier, it will remain in that state until  404  is reset by an external button (called non revertive). If another amplifier should fail during that time, no switching will occur. Also  404  can be set to revert communication back to the working amplifier after a predefined time period, if the alarm from that amplifier has cleared. 
         [0018]    In order to test the operability of protection switch, test buttons are installed to induce failures for the scenarios mentioned above. These buttons will simulate an alarm received from either the west, east, or protection amplifiers. This will allow installers and technicians the ability to verify the operability of amplifier  108  from time to time. 
         [0019]      FIG. 5 . is a table that demonstrates which position the optical switches are set to in the four different scenarios. The first, is the normal operation, in which all the switches are set to their normal positions as indicated by  FIG. 1 . Should amplifier  106  fail, the switches orient themselves according to the column titled “East Amp ( 106 ) Failure”, further illustrated by  FIG. 2 . Should amplifier  107  fail, the switches orient themselves according to the column titled “West Amp ( 107 ) Failure”, further illustrated by  FIG. 3 . Should amplifier  108  fail, the switches orient themselves according to the column titled “Prot. Amp ( 108 ) Failure”, further illustrated by  FIG. 1 . “N” indicates operating normally, and “S” indicates it is switched from its normal operation. 
         [0020]    For the protection of an optical network with more than two optical amplifiers, the protective switch must be modified in order to accommodate the extra amplifiers. This is achieved by adding to and/or modifying the optical switches and combiners to the invention&#39;s design but does not deviate from the scope of this invention.