Fiber optic frequency transfer link

A stabilized fiber-optic reference frequency distribution system has been fabricated and tested. The distribution system is designed to transmit a 100-MHz reference signal, which is generated by a hydrogen maser frequency standard, over a distance of 22 km. The goal is to maintain a stability of 1 part in 10¹⁷ for 1000-s averaging times. The stabilizer circuitry reduced delay variations that result from the effect environmental changes, such as temperature, on the fiber. The distribution system was designed using a computer simulation program that allows the delays, bandwidths, gains and damping factors to be varied for optimum performance. A breadboard version of the stabilizer was fabricated and tested in an environmentally controlled test chamber. In preliminary tests, the stabilizer reduced phase variations caused by temperature changes of 20°C by as much as 45 times