Delivery of high-stability optical and microwave frequency standards over an optical fiber network

Optical and radio frequency standards located in JILA and National Institute of Standards and Technology (NIST) laboratories have been connected through a 3.45-km optical fiber link. An optical frequency standard based on an iodine-stabilized Nd:YAG laser at 1064 nm (with an instability of ∼4x10-14 at 1 s) has been transferred from JILA to NIST and simultaneously measured in both laboratories. In parallel, a hydrogen maser-based radio frequency standard (with an instability of ∼2.4x10-13 at 1 s) is transferred from NIST to JILA. Comparison between these frequency standards is made possible by the use of femtosecond frequency combs in both laboratories. The degradation of the optical and rf standards that are due to the instability in the transmission channel has been measured. Active noise cancellation is demonstrated to improve the transfer stability of the fiber link