Spectral gain and noise evaluation of SOA and SOA-based switch matrix

The spectral dependence of the gain and noise figure of a 1.55 µm semiconductor optical amplifier (SOA) in linear and saturated operation is calculated using an accurate description of the population inversion factor nsp using a detailed density-matrix gain model, and taking longitudinal nonuniformity of carrier density into account by properly sectioning the device. Results show that the lowest noise figure is always attained at a wavelength longer than the gain peak, and that the −3 dB gain bandwidth increases in saturated operation. The performance of a SOA-based 4×4 InP switch matrix is analysed. When the matrix is in the ‘on’ state, it is equivalent to a cascade of three SOAs, which are analysed using longitudinal sectioning of each device, and by taking into account the amplified spontaneous emission (ASE) propagating forward and backward within the matrix. The influence of input/output passive splitter loss on the spectral noise figure of the matrix is also assessed.