Practical evaluation of a 50 km fiber link utilizing a commercial modem

Abstract

We evaluate the stability of two-way time and frequency transfer over a 50 km fiber optic link established using a commercially available fiber optic modem. For this evaluation we report the residual phase noise, total Allan deviation, total time deviation, and temperature fluctuations of the optical time and frequency transfer network. This two-way transfer is transmitted over an underground, dark fiber optic path in an urban environment. The measurement serves as a practical evaluation for establishing a long term fiber optic link between clocks or timescales intended for synchronization over short baselines where dark fiber may be available. In addition to measuring the time and frequency transfer stability we discuss other obstacles in fiber optic communication such as patch insertion loss and fiber availability.