A fiber optic gyroscope on multiplexed telecommunication network with a large enclosed area

This work describes the realization of a fiber optic gyroscope with a sensitivity of 10
^-8
(rad/s)/√Hz. Such a high sensitivity is obtained using a 47 km long single mode fiber of the urban optical telecommunication network, that is shared with other users and encloses an area of 20 km
²
. This setup has been used to investigate ground motion in occurrence of earthquakes.