Two-way time and frequency transfer using optical fibers

The National Institute of Standards and Technology (NIST) has built a two-way time-transfer device which uses any currently unused byte in the SONET (SDH) overhead to effect time transfer. The hardware shows stability which allows time transfer over short distances (km) with stabilities less than 10 ps. Time transfer over distances that require additional amplifiers in the fiber have not yet been investigated. Accuracy at the same level should also be possible.