Influence of Raman scattering on quantum noise in phase-sensitive amplification in a fiber

Kyo Inoue

Kyo Inoue

Phase-sensitive amplification (PSA) can provide low-noise signal amplification, and a quantum-limited noise figure of 0 dB, that is, additional noise-free amplification, is theoretically achievable. However, in fiber-based single-pumped PSA systems, it has been reported that Raman scattering in the fiber degrades the noise figure from the ideal 0 dB. In the present study, the influence of Raman scattering on quantum noise in dual-pumped degenerate PSA in a fiber is investigated. A quantum mechanical treatment starting from the Heisenberg equation of motion is developed, considering the parametric interaction and Raman interaction simultaneously, and an analytical expression for the noise figure is derived. An example of calculation is also presented, which quantitatively indicates the degradation in the noise figure due to Raman scattering.

Colin J. McKinstrie, M. G. Raymer, Stojan Radic +1 more

Kyo Inoue

Wavelength dependence of quantum noise in nondegenerate phase-sensitive amplification in an optical fiber, where signal and its phase-conjugated idler lights are incident into a fiber together with pump light, is theoretically investigated. An analytical formula of the quantum-limited noise figure, that takes Raman scattering into account as well as parametric amplification, is derived based on full quantum mechanical treatment. Using the obtained formula, a calculation example of the noise figure spectrum is also presented, where the pump light phase is adjusted so that the signal gain is maximum at a phase-matched wavelength, supposing multichannel amplification.

R. C. Swanson, David C. MacPherson, John L. Carlsten

Kyo Inoue

Phase-sensitive amplification (PSA) based on nonlinear parametric interaction provides low-noise amplification such that the noise figure can be 0 dB in principle. However, when an optical fiber is used as a nonlinear medium for PSA, multiple four-wave-mixing (FWM) processes other than the PSA process are induced, which can degrade the PSA noise performance, especially in dual-pump PSA with a narrow signal-pump wavelength separation. This paper investigates the influence of multiple FWM processes on quantum noise of dual-pump PSA in an optical fiber. The noise figure is calculated using quantum-mechanical operators, considering multiple FWM processes with the PSA process. Calculation examples are also presented, which indicate that the noise figure is degraded by 0.2–0.4 dB from the ideal 0 dB, depending on the signal-pump wavelength separation and fiber parameters.