Spectrally flat and broadband doublepumped fiber optical parametric amplifiers

Abstract

We study theoretically and experimentally spectrally flat and broadband double-pumped fiber-optical parametric amplifiers (2P-FOPAs). Closed formulas are derived for the gain ripple in 2P-FOPAs as a function of the pump wavelength separation and power, and the fiber non-linearity and fourth order dispersion coefficients. The impact of longitudinal random variations of the zero dispersion wavelength $λ_0$ on the gain flatness is investigated. Our theoretical findings are substantiated with experiments using conventional dispersion shifted fibers and highly nonlinear fibers (HNLFs). By using a HNLF having a low variation of $λ_0$ we demonstrate high gain and flat spectrum ($25 \pm 1.5\text{ dB}$) over $115\text{ nm}$.