Phase-Noise Measurement of a Stabilized Single-Longitudinal-Mode Er³⁺-Doped-Fiber Laser

Abstract

The phase noise of highly coherent laser radiation can be critical when a laser is used as a source in an interferometric system. Such noise can lead to serious degradation of fringe visibility and, consequently, of the sensitivity of the interferometer as a transducer. Phase noise is closely related to frequency noise, that is, the time-dependent excursions of the laser oscillation wavelength about its average value. It is the amplitude of these excursions, as well as their frequency content, that determine both phase and frequency noise. By definition, spectral densities of phase noise and frequency noise differ by a factor proportional to f², which in practice means that phase noise, unlike frequency noise, is only important at low frequencies.