Optical buffers are important components of an optical switch in a high-speed optical network. We propose a model of a fiber loop buffer, which incorporates a semiconductor laser amplifier (SLA) as a nonlinear element controlled by an optical control signal. The impact of the accumulated and amplified spontaneous emission noise of the SLA and the data pattern dependent gain saturation effect in the SLA on the properties of the buffer is taken into account to give the optimum operation conditions theoretically.