A new technique is proposed and demonstrated for improving the resolution of the delayed self-heterodyne method for laser spectral linewidth measurement. The delay time between two laser beams is increased by the use of multipass transmission in an optical fiber ring interferometer containing a frequency shifter. This technique does not require a longer fiber or complicated curve fitting of the observed spectra.
© 1990 Optical Society of America
Hidemi Tsuchida, "Simple technique for improving the resolution of the delayed self-heterodyne method," Opt. Lett. 15, 640-642 (1990)