Reducing temporal fluctuation of signal intensity in optical wave mixing

In electrical amplifiers, the common method to reduce the fluctuation of the output signal is known as feedback. We show that, in optical wave-mixing systems where the total energy of the pump and the signal is conserved, the fluctuation of the signal intensity can be greatly reduced by returning a portion of the output pump to the input pump. The advantage of the latter method is that the signal intensity is not reduced, whereas in the former method the output of the signal is reduced by the same factor as its relative fluctuation is reduced.