Low-cost bidirectional optical amplifier using a unidirectional Er-doped fiber amplifier and a fiber Mach-Zehnder interferometer

We propose a cost-effective bidirectional optical amplifier consisting of a single unidirectional Er-doped fiber amplifier and a fiber Mach-Zehnder interferometer (MZI), We demonstrated its feasibility by observing the optical spectra and measuring bit error rates when four optical signals were bidirectionally transmitted at 2.5 Gb/s over a 160-km single-mode fiber. A net gain of 17 dB and a power penalty of 0.5 db were obtained.