Gain characteristics of coherent optical amplifiers using a Mach-Zehnder interferometer with Kerr media

This paper investigates the gain characteristics of coherent optical amplifiers that amplify only one of two quadrature phase components in an input signal light according to the phase of pump light. It is constructed around a Mach-Zehnder interferometer with Kerr media. To heuristically obtain the design parameters of the coherent optical amplifier, small-signal analysis is adapted to the Mach-Zehnder interferometer with Kerr media. The theoretical results are then compared to experimental results and shown to agree well, which confirms the validity of this design approach. By utilizing low-loss and high-nonlinearity silica fiber as the Kerr medium and optimizing its length, a coherent optical amplifier is constructed that yields high-gain (up to 26 dB) operation.