Four-core Erbium-doped Fiber Amplifier for Bi-directional Transmission using PLC-type Directional Convertor

We demonstrate a four-core erbium-doped fiber amplifier designed for multi-core bidirectional transmission. By using a double-layered planar lightwave circuit with a built-in pump light combiner, we achieved a fan-in/fan-out-less isolatorshared configuration. C-band optical amplification with an average gain of 15.5 dB and a noise figure of 6.8 dB was achieved at the input signal power per core of 0 dBm. Our results demonstrate that the influence of the difference between up- and down-link input signal powers on the amplification performance can be managed by means of pump power control. However, we also found that a difference of more than 2 dB in the up- and downlink input signal power may have a negative effect on the power conversion efficiency.