Fibre Bragg filters for pump rejection and recycling in erbium doped fibre amplifiers

Abstract

Residual pump light emitted from an optical fibre amplifier can be a problem in a telecommunication system. The performance of a receiver can be adversely affected by the residual pump power emitted from a pre-amplifier, which is usually larger than the signal power, because it can cause excess noise and receiver saturation. A pre-amplifier which is designed for optimum gain and minimum noise figure will therefore have a large emission of unabsorbed pump light. If the unabsorbed pump light can be reflected back into the amplifier then the amplifier performance will be increased and the receiver will be free from pump light. We show for the first time how this can be achieved with an efficient wavelength dependent fibre reflection filter.