A comparison between the noise characteristics of single-pump and dual-pump fiber optical parametric amplifiers is theoretically carried out in terms of the noise figure, accounting for the amplified quantum noise and the excess pump noise. (2 pages)
For the first time, four different noise sources, which are amplified quantum noise, Raman phonon seeded excess noise, pump transferred noise (PTN), and pump residual noise, are considered simultaneously to model the wavelength-dependent noise figure in a single-pumped fiber optical parametric amplifier. An asymmetric signal NF spectrum induced by both Raman phonon seeded excess noise and Raman gain modified PTN is measured in the electrical domain. Theoretical results agree very well with the experimental data. The idler NF spectrum is also analyzed and measured, which shows a more symmetric profile.
We derive an analytical theory for the noise figure of an undepleted and lossless fiber optical parametric amplifier (FOPA). Both the signal and the wavelength converted idler are investigated. Our theory is applicable for both an ideal pump power source, as well as a noisy one. We find that a noisy pump source can severely degrade the performance at high gain due to the stochastic gain-variations the signal and idler will experience. The theory is compared with Monte Carlo simulations of the FOPA and an excellent agreement is obtained. Simulations in the gain-depleted region show the possibility to reach below quantum-limited, phase-insensitive amplification for single channel transmission.
Dual-pump fiber optical parametric amplifiers offer wide, flat gain spectra across arbitrary wavelengths, often outperforming the use of single-pump designs. However, gain flatness depends on the pump frequencies’ center of gravity relative to the nonlinear fiber’s zero-dispersion wavelength. This study experimentally investigated the gain, gain flatness, and noise figure of degenerate dual-pump fiber-optic phase-sensitive amplification at various separations between these points. We demonstrated 38 dB gain with 1.5 dB gain flatness variation over a 30 nm bandwidth as well as a noise figure below the conventional 3 dB quantum limit for a degenerate signal.