Abstract:
An errorless switching system is disclosed that is comprised of a fault detector, a synchronization system, and a switching system. The synchronization system aligns a first data signal and a second data signal. The fault detector detects errors in the data signals and instructs the switching system to transfer the first data signal or the second data signal to avoid transferring the erroneous data. No data is lost or duplicated because the data signals are aligned at the switching system.

Description:
RELATED APPLICATIONS 
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     FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
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     MICROFICHE APPENDIX 
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     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention is related to the field of fiber optic communication systems, and in particular, to fiber optic systems that provide errorless switching. 
     2. Description of the Prior Art 
     FIG. 1 depicts the current system of switching used in fiber optic networks. A first node  101  connects to a second node  102  via a first optical fiber  150  and a second optical fiber  160 . The second node  102  is comprised of a first optical-to-electrical converter  120 , a second optical-to-electrical converter  121 , a first fault detector  130 , a second fault detector  131 , and a switching system  140 . The first optical-to-electrical converter  120  connects to the first node  101  via the first optical fiber  150 . The first optical-to-electrical converter  120  connects to the first fault detector  130  via electrical data line  151 . The first fault detector  130  connects to the switching system  140  via electrical data line  153  and electrical control line  152 . 
     The second optical-to-electrical converter  121  connects to the first node  101  via the second optical fiber  160 . The second optical-to-electrical converter  121  connects to the second fault detector  131  via electrical data line  161 . The second fault detector  131  connects to the switching system  140  via electrical data line  163  and electrical control line  162 . 
     In operation, the first node  101  transmits a first data signal over the first optical fiber  150 . The first optical-to-electrical converter  120  receives the first data signal and converts it from an optical signal to an electrical signal. The first optical-to-electrical converter  120  transfers the first data signal to the first fault detector  130  via electrical data line  151 . The first fault detector  130  determines if an error has occurred in the transmission of the first data signal and generates a first error instruction if an error has occurred. The first fault detector  130  transfers the first data signal to the switching system  140  via electrical data line  153 . The first fault detector  130  transfers any first error instructions to the switching system  140  via electrical control line  152 . 
     The first node  101  transmits a second data signal over the second optical fiber  160 . The second optical-to-electrical converter  121  receives the second data signal and converts it from an optical signal to an electrical signal. The second optical-to-electrical converter  121  transfers the second data signal to the second fault detector  131  via electrical data line  161 . The second fault detector  131  determines if an error has occurred in the transmission of the second data signal and generates a second error instruction if an error has occurred. The second fault detector  131  transfers the second data signal to the switching system  140  via electrical data line  163 . The second fault detector  131  transfers any second error instructions to the switching system  140  via electrical control line  162 . 
     The switching system  140  receives the first data signal, the second data signal, and any first or second error instructions. The switching system  140  transfers either the first data signal or the second data signal. The signal that gets transferred depends on the first error instruction and the second error instruction. For example, if an error occurs on the first data signal, the first error instruction instructs the switching system  140  to transfer the second data signal and not the first data signal. If an error occurs on the second data signal, the second error instruction instructs the switching system  140  to transfer the first data signal and not the second data signal. 
     Two problems exist with the system in FIG.  1 . One problem is that duplicate data can be transferred in the switching process. For example, consider the situation where the second data signal lags behind the first data signal. The lag in the second data signal causes the signals to be mis-aligned at the switching system  140 . Assume for this example that the second data signal lags the first data signal by ten blocks of data. When the switching system  140  changes from transferring the first data signal to transferring the second data signal, those ten blocks of data have already been transferred on the first data signal. After the switching system  140 , the ten blocks of data will again be transferred on the second data signal. The amount of duplicated data depends on how far the second data signal lagged behind the first data signal. 
     Another problem is that data can be lost in the switching process. Consider the other situation where the first data signal lags behind the second data signal. The lag in the first data signal causes the data to be mis-aligned at the switching system  140 . Assume for this example that the first data signal lags the second data signal by ten blocks of data. When the switching system  140  changes from transferring the first data signal to transferring the second data signal, ten blocks of data will have been missed. The amount of data lost depends on how far the first data signal lags behind the second data signal. 
     Errorless switching exists in other communications networks such as microwave communication networks, but doesn&#39;t exist in fiber optic systems. Fiber optic communication networks traditionally utilize Synchronous Optical Network (SONET) rings to provide two transmission paths to switch between. These fiber optic communication networks do not provide for errorless switching. By today&#39;s standards, switching resulting in duplicate or lost data is not acceptable. 
     SUMMARY OF THE SOLUTION 
     The invention solves the above problem by aligning the first data signal with the second data signal in the optic node before switching occurs. Data is not lost or duplicated in the switching process. 
     The errorless switching system is comprised of a first fault detector, a second fault detector, a synchronization system, and a switching system. The synchronization system aligns the first data signal with the second data signal. The fault detectors detect errors in the data signals and instruct the switching system to transfer the first data signal or the second data signal to avoid transferring erroneous data. No data is lost or duplicated because the data signals are aligned at the switching system. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is prior art and is an example of a switching network in a fiber optic system. 
     FIG. 2 is an example of the invention showing a switching network in a fiber optic system that provides errorless switching. 
     FIG. 3 is an example of two data signals being mis-aligned as they enter an optic node and then becoming aligned before reaching a switching system. 
     FIG. 4 is an example of two data signals being mis-aligned as they enter an optic node and then becoming aligned before reaching a switching system. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     System Configuration and Operation—FIGS. 2-4 
     FIG. 2 depicts a specific example of an errorless switching network in accord with the present invention. Those skilled in the art will appreciate numerous variations from this example that do not depart from the scope of the invention. Those skilled in the art will also appreciate that various features could be combined to form multiple variations of the invention. 
     FIG. 2 shows a first node  201  connected to a second node  202  via a first optical fiber  250  and a second optical fiber  260 . The second node  202  is comprised of a first optical-to-electrical converter  220 , a second optical-to-electrical converter  221 , a first fault detector  230 , a second fault detector  231 , a synchronization system  290 , and a switching system  240 . The first node  201  connects to the first optical-to-electrical converter  220  via the first optical fiber  250 . The first optical-to-electrical converter  220  connects to the first fault detector  230  and the synchronization system  290  via electrical data line  251 . The first fault detector  230  connects to the switching system  240  via electrical control line  252 . The synchronization system  290  connects to the switching system  240  via electrical data line  253 . 
     The first node  201  connects to the second optical-to-electrical converter  221  via the second optical fiber  260 . The second optical-to-electrical converter  221  connects to the second fault detector  231  and the synchronization system  290  via electrical data line  261 . The second fault detector  231  connects to the switching system  240  via electrical control line  262 . The synchronization system  290  connects to the switching system  240  via electrical data line  263 . 
     Those skilled in the art will appreciate that the switching system  240  is any electronic switch, optical switch, transistor, circuit, processor, buffer, memory controller, gate array, or any other device or method for transferring one of two, or more, data signals when commanded. Likewise, the synchronization system  290  is any system that can align two or more signals. 
     In operation, the first node  201  transmits a first data signal over the first optical fiber  250 . The first node  201  also transmits a second data signal over the second optical fiber  260 . The first data signal and the second data signal are typically unaligned. The first optical-to-electrical converter  220  receives the first data signal and converts it from an optical signal to an electrical signal. The first optical-to-electrical converter  220  transfers the first data signal to the first fault detector  230  and the synchronization system  290  via electrical data line  251 . The first fault detector  230  determines if an error has occurred in the transmission of the first data signal, and generates a first error instruction if an error has occurred. The first fault detector  230  transfers any first error instructions to the switching system  240  via electrical control line  252 . The synchronization system  290  receives and aligns the first data signal and the second data signal. The synchronization system  290  transfers the first data signal to the switching system  240  via electrical data line  253  and the second data signal via electrical data line  263 . 
     As stated above, the first node  201  sends the second data signal over the second optical fiber  260 . The second optical-to-electrical converter  221  receives the second data signal and converts it from an optical signal to an electrical signal. The second optical-to-electrical converter  221  transfers the second data signal to the second fault detector  231  and the synchronization system  290  via electrical data line  261 . The second fault detector  231  determines if an error has occurred in the transmission of the second data signal, and generates a second error instruction if an error has occurred. The second fault detector  231  transfers any second error instructions to the switching system  240  via electrical control line  262 . 
     FIG. 3 shows a data-level view of the system in FIG. 2 in operation. The first data signal, shown in the form of blocks of data, travels on electrical data line  251  from the optical-to-electrical converter  220  to the synchronization system  290 . The second data signal, shown in the form of blocks of data, travels on electrical data line  261  from the optical-to-electrical converter  221  to the synchronization system  290 . Each sequential number  1 - 14  in FIG. 3 represents a block of data. The first data signal is the same as the second data signal except for an error  310  in the first data signal. The signals are mis-aligned with the second data signal lagging behind the first data signal when they enter the synchronization system  290 . The synchronization system  290  aligns the first data signal and the second data signal before the signals reach the switching system  240 . 
     The first data signal contains the error  310 . If the data signals remained unaligned, switching from first data signal to second data signal to avoid the error  310  would result in duplicate data being transferred. A later switch back to the first data signal from the second data signal would result in a loss of data. With the data signals aligned by the synchronization system  290 , switching from the first data signal to the second data signal to avoid the error  310  does not result in duplicate or lost data. 
     FIG. 4 represents the same concept as FIG. 3 except the first data signal lags behind the second data signal. The first data signal contains the error  310 . If the data signals remained unaligned, switching from the first data signal to the second data signal to avoid transferring the error  310  would result in data being lost. A later switch back to the first data signal from the second data signal would result in duplicate data being transferred. With the data signals aligned by the synchronization system  290 , switching from the first data signal to the second data signal to avoid the error  310  does not result in duplicate or lost data. 
     Those skilled in the art will appreciate variations of the above-described embodiments that fall within the scope of the invention. As a result, the invention is not limited to the specific examples and illustrations discussed above, but only by the following claims and their equivalents.