Light amplifier having a multi-stage optical isolator

摘要

A light amplifier is constructed with only one multi-stage optical isolator so as to reduce the size thereof and to lower the fabrication cost thereof. The multi-stage optical isolator has two input ports and two output ports for cutting-off a reverse flow of a forwarding light when a following input light enters a first input port and when an output light enters a second input port. A source pump generates light used to amplify weak input light. A wavelength division multiplexer division-modulates wavelengths of the light generated by the source pump and the light forwarded through the multi-stage optical isolator. An optical fiber amplifies the light from the wavelength division multiplexer, and emits the amplified light through the first port of the multi-stage optical isolator.