Comparison between co- and counter-propagative optical injection near the transparency wavelength on SOA static and dynamic performances

A comparison between semiconductor optical amplifier (SOA) performance enhancement, when injecting a CW assist light into the cavity at gain transparency wavelength in both co- and counter-propagative directions with respect to the optical input signal, is presented. Experimental results point out that the counter-propagative configuration is better performing than the co-propagative one. Consequently, injecting an assist light power of 19 dBm at 1480 nm in the counter-propagative (respectively, co-propagative) direction does not only increase the SOA saturation output power by 4 dB (resp. 1.5 dB) but also speeds up the gain recovery time by a factor of two (resp. 1.3). Numerical investigation of the carrier density spatial distribution in both injection directions is also given.