Abstract:
The optical fiber pumping 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:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention is related to the field of optical fiber pumping 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. 
     2. Description of the Related Art 
     Typical optical fiber pumping systems include a “soft-fail” design that uses redundant pumps to prevent downtime when one of the pumps fails. For example, a optical fiber pumping system which includes at least two pump lasers that feed their 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. 
     Other conventional optical fiber pumping systems provide protective switching that re-route the signal to other parallel optical fiber pumping systems around the failed optical fiber pumping system. Such 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 systems require redundant optical fiber pumping systems which adds a great deal of expense. 
     SUMMARY OF THE INVENTION 
     The invention is an optical fiber pumping system that enables a hot swap of a failed pump. The optical fiber pumping system includes an external connector that enables an external pump laser to be connected to the optical fiber pumping system. The external connector communicates with a pump multiplexer that also receives an input from the on-board pump laser. The pumping system may also include an onboard connector that is positioned between the on-board pump laser and the pump multiplexer to break the connection between a failed on-board pump laser and the pump multiplexer. 
     The optical fiber pumping system of the present invention may also include a gain control system that coordinates the shut down of the on-board pump laser with the power up of an external pump laser system. 
     The external pump laser system may include a plurality of pump lasers whose combined or averaged output wavelength approximates the wavelength of the on-board pump laser. 
     The external pump laser system may include inexpensive but high power sources since the reliability of the external power source does not need to be high. 
     Additionally, any number of on-board pumps may be replaced using the external pumping system. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     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 
     FIG. 1 shows a schematic diagram of an optical fiber pumping system  10  in accordance with the present invention. The optical fiber pumping system includes an external pump  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 connector  16  is in communication with a pump/signal 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 a pump  20  in communication with a connector  22 . The pump/signal multiplexer  18  is in communication with another pump/signal multiplexer  24  that communicates with a signal line  26 . The signal line  26  receives an input signal and communicates with pump/signal multiplexer  24  in communication with output signal line  28 . 
     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, other conventional optical fiber system components or the like. 
     The optical fiber pumping system  10  may operate by a failure 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. 
     Once it is determined that the pump has failed in some manner, a technician may connect an external pump system  12  to the connector  16 . The external pump system 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 connector  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 multiplexer  24 . 
     The power up of the external pump system  12  and the power down of the on-board 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 onboard 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 onboard pump and the external pump. It is also conceivable that an optical fiber pumping system may include spare onboard pump that is controlled to compensate for a failed onboard pump until that failed pump is replaced. 
     If the multiplexer  18  operates on a specific wavelength and the external pump system  12  operates on a different wavelength, then spectral changes in the output of the multiplexer  18  may occur due to pump wiggle. 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 on-board 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. 
     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 . Additionally, 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 1xn switch (not shown) to a single external pump system that may be automatically routed to any amplifier with a failing pump. 
     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.