Abstract:
The optical fiber system includes a connector that is adapted to selectively communicate with an external pump system. The connector communicates with an onboard pump multiplexer which also receives input from an on-board pump via a connector. The on-board pump may be hot swapped by connecting an external pump system to the connector and coordinating the power up of the external pump system with the power down of the on-board pump to replace a failed on-board pump with a new pump.

Description:
[0001]    This application is continuation in part of U.S. patent application Ser. No. 09/793,117, filed on Feb. 27, 2001, the benefit of priority of which is hereby claimed. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    This invention is related to the field of optical fiber systems. More particularly, the invention is directed to a system and apparatus that enables swapping of optical amplifier pumps from an onboard optical fiber system while the optical fiber system is operating.  
           [0004]    2. Description of the Related Art  
           [0005]    Typical optical fiber systems include a “soft-fail” pumping design that uses redundant optical pumps to prevent downtime when one of the optical pumps fails. For example, such an optical fiber system may include at least two pump lasers that provide optical power into a conventional coupler that combines the outputs of each pump laser into a single output. In this manner, the failure of one of the pump lasers results in a corresponding percentage decrease in the amplification ability of the optical fiber pumping system. For example, if the optical fiber pumping system includes two pump lasers, failure of one of the pump lasers will typically result in an output of only fifty percent of the designed output. These systems often include monitors that indicate when a pump has failed, thus, when a pump has failed, an operator may take the entire optical pumping system off-line and replace the failed pump laser with a new pump laser.  
           [0006]    Other conventional optical fiber systems provide protective switching that re-route the signal to other parallel optical fiber pumping systems around the failed optical fiber pumping system. Such optical fiber systems completely remove the load from the optical fiber pumping system and enable a technician to remove and service the entire optical fiber pumping system. Such optical fiber systems require redundant optical fiber pumping systems which adds a great deal of expense.  
         SUMMARY OF THE INVENTION  
         [0007]    The invention is an optical fiber system that enables a hot swap of a failed pump. The optical fiber system includes an external connector that enables an external pump to be connected to the optical fiber system. The external connector communicates with a pump multiplexer that also receives an input from the internal optical pump. Such an internal optical pump may be, for example, an on-board pump laser. The optical fiber system may also include an onboard connector or switch that is positioned between the internal pump and the pump multiplexer to break the connection between the failed on-board pump laser and the pump multiplexer.  
           [0008]    The optical fiber system of the present invention may also include a gain control system that coordinates the shut down of the internal pump laser with the power up of an external pump.  
           [0009]    The external pump may include one or a plurality of pump lasers whose combined or averaged output wavelength approximates the wavelength of the internal pump laser.  
           [0010]    According to one embodiment of the present invention, the external pump system may include inexpensive but high power laser sources because the reliability of the external pump laser does not need to be high.  
           [0011]    Additionally, according to an embodiment of the present invention, any number of optical pumps may be replaced using the external pumping system. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0012]    [0012]FIG. 1 is a schematic diagram of one embodiment of an optical fiber pumping system in accordance with the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0013]    [0013]FIG. 1 shows a schematic diagram of an optical fiber system  10  in accordance with the present invention. The optical fiber system includes an external pump system  12  and an on-board optical pumping system  14 . The on-board optical pumping system  14  includes a connector  16  that is adapted to communicate with the external pump system  12 . The external pump system  12  may include one or more external pumps  12 ′. The connector  16  is in communication with a pump multiplexer  18 . The connector  16  may be a bulkhead optical connector, a bare pig-tail, a connectorized pig-tail or the like. The on-board optical pumping system  14  also includes an optical pump  20  in communication with a switch (or connector)  22 . The pump multiplexer  18  is in communication with a pump/signal multiplexer  24  that communicates with an optical signal line  26 . Pump multiplexer  18  multiplexes or combines pump light propagating through fibers  27 A and  27 B which is provided into fiber  27 C. That is, the total pump power provided by the optical fibers  27 A and  27 B is directed by the pump multiplexer  18  to fiber  27 C. Pump multiplexer  18  may operate via polarization or wavelength-multiplexing and, may be utilized in conjunction with constraints on the wavelengths and/or polarization states of the pump light propagating through fibers  27 A and  27 B. The signal line  26  receives input optical signal and communicates with pump/signal multiplexer  24  in communication with multiplexer output signal line  28 . That is, multiplexer  24  combines both pump energy and the input signal and provides the combined pump/signal light via line  28  to a rare earth doped coil. Alternatively, line  28  may be connected to a Raman gain fiber. The signal line  26  and the pump signal line  28  may be in the form of optical fiber.  
         [0014]    One of ordinary skill in the art understands that the on-board optical fiber pumping system  14  may also include many other conventional components that condition the input signal to provide the output signal, which are not shown for the purpose of clarity. For example, the on-board optical fiber pumping system may include any number of additional input signal lines, additional pumps  20 , pump/signal multiplexers, isolators, band pass filters, erbium-doped fiber, signal gain elements, other conventional optical fiber system components or the like.  
         [0015]    The operation of optical fiber system  10  may be compromised by a failure or degradation of pump  20  on the on-board optical pumping system  14  being detected. Pump failures may include a minor degradation in the pump that may be determined by a performance monitoring apparatus (not shown) in communication with the pump  20 . Additionally, inferences may be drawn regarding the pump degradation by monitoring the electrical current required by the pump  20  to maintain a given level of pump  20  output. Additionally, a degradation of the pump may be inferred by increased cooling requirements of the on-board pumping system  14 . A failing pump  20  may require additional cooling to maintain a given level of output.  
         [0016]    Once it is determined that the internal pump has failed in some manner, a technician may connect an external pump system  12  to the connector  16 . The external pump system  12  may have one or more optical pumps  12 ′. The external pump system  12  may then be powered up and the pump  20  may be powered down in a coordinated manner so that the pump/signal multiplexer  24  does not receive a widely varying input. After the pump  20  is powered down, the switch  22  may be disconnected and the failed pump  20  may be removed from the on-board optical fiber pumping system  14 . A new optical pump  20  may then be installed into the optical fiber pumping system  14 . The switch  22  may then be closed and the new pump  20  may be powered up in a coordinated manner with the power-down of the external pump system  12  to avoid widely varying inputs to the pump signal multiplexer  24 .  
         [0017]    The power up of the external pump system  12  and the power-down of the on-board (i.e. internal) pump  20  may be controlled by an automatic gain control system (not shown). An automatic gain control system may be necessary depending upon the automatic gain control alarms and monitors that are available to set the external pump. However, it is also desirable to provide an automatic gain control system to permit continuous operation of the on-board gain control. The automatic gain control system may include multiple independent gain control systems that are coordinated and/or a single gain control system that is adapted to control both the on-board pump and the external pump. It is also conceivable that an optical fiber pumping system may include spare on-board pump that is controlled to compensate for a failed on-board pump until that failed pump is replaced.  
         [0018]    If the internal pump  20  operates on a specific wavelength and the external pump system  12  operates on a different wavelength, then spectral changes in the output of the optical fiber system  10  may occur. If such spectral changes are unacceptable, the external pump system may include a plurality of multiplexed pumps with an average wavelength that is equal to the pump  20 . It is to be understood that the present invention may be used with any type of multiplexer such as a polarizing multiplexer, a wavelength multiplexer or the like.  
         [0019]    One of ordinary skill in the art understands that the on-board pumping system  14  may contain many more multiplexers than are shown in FIG. 1. Furthermore, to accommodate the external pump system  12  additional multiplexers  18  may be added upstream or downstream of the existing on-board multiplexers. Alternatively, additional external connectors  16  may be provided to the on-board optical pumping system  14 . In any case, many modifications may be made to the embodiment shown in FIG. 1 to ensure the correct distribution of pump power through the amplifier in all circumstances. One of ordinary skill in the art also understands that any number of amplifiers on the on-board optical fiber pumping system  14  may be connected through a 1×n switch (not shown) to a single external pump system  12  that may be automatically routed to any amplifier with a failing pump.  
         [0020]    While various embodiments in accordance with the present invention have been shown and described, it is understood that the invention is not limited thereto, and is susceptible to numerous changes and modifications as known to those skilled in the art. Therefore, this invention is not limited to the details shown and described herein, and includes all such changes and modifications.