Noise in semiconductor optical amplifiers (SOA)

Analytical method of noise in the semiconductor optical amplifier (SOA) has not been established yet. The basic problem is how introduce quantized optical field with the Langevin noise sources in the open wave guide, because the SOA has not have facets mirrors to confine the optical field in the device. The author's group introduced an idea to define finite size of photons based on the quantum mechanical property of the spontaneous emission. The longitudinal mode for the traveling optical field is defined for optical signal and the generated spontaneous emission. Then, the intensity (IM) noise, the frequency (FM) noise and the spectral linewidth were theoretically calculated. Characteristics of these noise were also experimentally confirmed.