Horn-Waveguide RSOA-EAM as a Colorless Emitting Source With Reduced Crosstalk

We proposed, designed, and fabricated a monolithically integrated horn-waveguide asymmetric reflective semiconductor optical amplifier electro-absorption modulator (RSOA-EAM) to discriminately process down- and up-stream signals for colorless optical network units in the wavelength-division multiplexing passive optical network (PON). It is demonstrated that the horn-waveguide RSOA-EAM can effectively saturate the downstream signal and linearly amplify the upstream signal, an indispensable feature that is required by the RSOA-EAM to simultaneously erase the downstream signal for a clean seed and to amplify the reloaded upstream signal in its return path. The measurement shows that our fabricated device can reduce the extinction ratio of the 10-Gb/s downstream signal from 5 to 1.2 dB, and a 5-Gb/s upstream signal can be reloaded onto the “clean” carrier, with a clear eye-opening after the linear amplification of its power to over 1 dBm. The measured bandwidth of the device is 25 nm (from 1571 to 1596 nm), far beyond the required 5-nm (from 1575 to 1580 nm) colorless operating range for downstream signals in the 10-Gb/s Ethernet PON and X Gb/s PON.