Characterization of Phase-Sensitive and Phase-Insensitive Fiber Optical Parametric Amplifiers

Licentiatavhandling, 2010

The topic of this thesis is fiber optical parametric ampliers (FOPA). A unique feature of such ampliers is that they can operate in both phase-insensitive and phase-sensitive mode. The latter offers the potential of amplification without any added noise. FOPAs are based on a fiber nonlinearity known as four-wave mixing (FWM) and require one or two high-power optical pump waves. In addition to amplifying the signal, a new wavelength component, called the idler wave, will be generated. Two problems for all kinds of FOPAs are the stimulated Brillouin scattering (SBS) effect that can limit the pump power, and the fact that the nonlinear fibers have a non-uniform dispersion. A method for suppressing the SBS and simultaneously controlling the dispersion is presented and evaluated. By using two pumps, flat and broadband gain can be achieved, but this is typically limited by the available pump wavelengths. The generation of a high-power pump outside the conventional wavelength range is demonstrated, and applied in a two-pump FOPA with very broadband gain. To operate in phase-sensitive mode, the FOPA requires the idler wave to be present at the input, and that all waves are phase-correlated. The use of a first stage based on FWM to achieve this is presented, and a second stage operating in phase-sensitive mode is characterized in terms of gain, and in another experiment, the unique phase-squeezing property was characterized using a coherent receiver. This property is also exploited to demonstrate all-optical phase regeneration of phase-encoded data.