National standards of length for high-capacity optical fiber communication systems

— Development of fiber-based optical frequency combs —

Abstract

An optical frequency comb is a collection of laser modes with identical frequency intervals in the visible to near-infrared regions that enables direct comparison of optical frequencies with microwave atomic frequency standards. Traditional solid-state laser-based frequency comb systems are large, expensive, and very difficult to operate for long periods of time during experiments. From an early stage of development, we proposed fiber lasers as a feasible means of achieving a reliable frequency comb. After we succeeded in developing an in-house fiber-based frequency comb at the National Institute of Advanced Industrial Science and Technology (AIST), we made further advances, including calibration of the optical telecommunication band, establishment of national standards of length, and development of a narrow-linewidth comb for optical lattice clocks.