Realisation of the metre by optical frequency comb: applications in length metrology

The frequency comb of a femtosecond laser can be used like a ruler for length metrology. This permits measuring absolute distances with direct traceability to the atomic Cesium clock of the time standard. Optical frequency combs have received much attention in recent years due to their enormous potential in optical frequency metrology applications. We have studied an Erbium doped femtosecond fiber laser for applications in optical frequency metrology and found agreement of the measured frequency to within 2x10(-14). It has a number of advantages over other femtosecond lasers due to its greater compactness, long-term operation with less power consumption, compatibility with existing fiber optics and covering of the telecommunication range. With this system, the Spanish Centre of Metrology is establishing a new practical realization of the metre with an improved accuracy in two orders of magnitude with respect to the current system based on iodine stabilized lasers.