Dual comb spectroscopy for measuring the group velocity dispersion of optical fiber realized by fast locking of the beat note with a piezoelectric module*

Dual-comb spectroscopy (DCS) emerged a decade ago as a powerful tool for gas spectroscopy and metrology. DCS is based on two optical frequency combs (OFCs) with slightly different repetition rates. Using DCS, one can simultaneously obtain amplitude and phase of the light, resulting in the direct determination of complex refractive index. Thus, DCS promises for investigating the solid state materials.
Here, we demonstrate an application of measuring the group velocity dispersion (GVD) of single-mode fiber (SMF) by using DCS. We constructed two Er-fiber-based OFCs and achieved the fast locking of the beat note by using PZT module based on Ref. [1]. The beat note was phase locked with the servo bandwidth of over 100 kHz and the integrated phase noise as 0.21 rad and we realized the DCS system. By using this system, we obtained a wavelength-dependent GVD of SMF and the GVD as -22.0 ps^2/km at 1550 nm with the standard deviation of 0.02 ps^2/km. It agrees well with the nominal value of the GVD. Thus, we conclude that our DCS works as a brilliant tool for solid state physics.
Reference
[1] L. C. Sinclair et al., Rev. Sci. Instrum. 86, 081301 (2015).