Abstract: A hybrid amplifier reduces the noise generated by the hybrid amplifier. The hybrid amplifier includes a rare-earth doped fiber amplifier such as an EDFA (erbium-doped fiber amp), a Raman amplifier, a controller and a memory device. Noise is reduced by determining a gain balance between the EDFA and Raman amp that minimizes the noise figure. The controller performs a method that generates a plurality of functions relating the hybrid amp noise figure and the Raman gain for a particular span loss. These functions are then utilized to determine the Raman gain portion of the gain balance that minimizes the noise figure. The remaining portion of the gain balance is made up by the EDFA. For a hybrid amplifier that will see only one span loss value, then only one such function needs to be generated. Furthermore, the memory device of the hybrid amplifier can be programmed to store an optimum control curve that minimizes the noise figure for one or a plurality of span losses.

Abstract: Systems and methods for determining the distributed gain properties of a fiber plant are disclosed. A detector, a controller and a memory device are utilized to measure signal levels while the pump power is increased. The controller calculates gain for various pump power levels to construct a gain profile or transfer function which may be, for example, gain as a function of pump power. A gain transfer function is constructed for the particular fiber plant to which optical pump is connected. The constructed gain transfer function relates the output power of the optical pump and the signal gain of the signal travelling in the fiber plant. A controller utilizes the constructed gain transfer function to control the output power of the optical pump to produce a desired amount of signal gain. The gain transfer function may be stored as a look-up table and accessed by the controller to determine the amount of output power corresponding to a desired gain level.