Novel optical preamplifier with inverted ASE signal of semiconductor optical amplifier

We propose and demonstrate a novel optical preamplifier using an inverted signal of amplified spontaneous emission (ASE) of a semiconductor optical amplifier (SOA). The input signal is converted to the modulation of the ASE because of saturation characteristics. The proposed device can not only amplify optical signal but can also suppress the intensity noise of the input signal under the saturation regime. The receiver sensitivity was improved by 10 dB at 1 Gbit/s using the proposed preamplifier. Also, the intensity noise of a 1 Gbit/s spectrum-sliced light was significantly suppressed using the nonlinear characteristics of the preamplifier. A larger gain and a higher speed can be expected simultaneously at a lower input signal power by increasing the length of SOA. The proposed device will be useful in low cost access and metro networks.