Noise Figure Measurements in Phase-Insensitive and Phase-Sensitive Fiber Parametric Amplifier Cascades

For the first time, total NF below the phase-insensitive quantum limit of two cascaded non-degenerate in-line fiber parametric amplifiers without idler removal has been measured. About 1. 6dB NF has been estimated at >16dB gain for the second phase- sensitive stage after subtracting the excess noise from the first stage.