Linewidth measurements of a distributed feedback (DFB) fibre laser are made using delayed self heterodyne interferometry (DHSI) with both Mach-Zehnder and Michelson interferometer configurations. Voigt fitting is used to extract and compare the Lorentzian and Gaussian linewidths and associated sources of noise. The respective measurements are wL (MZI) = (1.6 ± 0.2) kHz and wL (MI) = (1.4 ± 0.1) kHz. The Michelson with Faraday rotator mirrors gives a slightly narrower linewidth with significantly reduced error. This is explained by the unscrambling of polarisation drift using the Faraday rotator mirrors, confirmed by comparing with non-rotating standard gold coated fibre end mirrors, © 2011 by the authors.
Canagasabey, A., Michie, A., Canning, J., Holdsworth, J., Fleming, S., Wang, H. C., & Åslund, M. L. (2011). A comparison of delayed self-heterodyne interference measurement of laser linewidth using mach-zehnder and Michelson interferometers. Sensors, 11(10), 9233–9241. https://doi.org/10.3390/s111009233