Low-drift fibre gyro using a superluminescent diode

A low-drift fibre-optic gyro, using a superluminescent diode to eliminate interferences between the transmitted and the reflected wave and make polarization control elements unnecessary, is investigated experimentally. The diodes, with an amplifying region of about 700 microns and an absorbing region of about 300 microns in length, were emitting at a wavelength of about 820 nm and had a spectral width of around 8 nm, corresponding to a coherence length of about 20 microns. The fiber coil showed a depolarizing behavior and, within the limit of measuring accuracy, no change of the scale factor occurred. During the 75 min. observation time, the RMS value for the bias uncertainty is indicated as 0.0028 degrees/s, with the residual drift thought to be related to some changes in the state of polarisation within the fiber coil.