Laser-driven optical gyroscope having a non-negligible source coherence length

A method of configuring a fiber-optic sensor, the method comprising:

• providing a fiber-optic sensor comprising a laser source and an optical fiber coil having a length, the coil optically coupled to the laser source such that light from the laser source is transmitted to the coil as a first signal propagating along the coil in a first direction and a second signal propagating along the coil in a second direction opposite to the first direction, wherein the optical paths of the first signal and the second signal are substantially reciprocal with one another and the first signal and the second signal are combined together after propagating through the coil to generate a third signal, the sensor having a phase noise which varies as a function of coherence length of the laser source;
• and
• selecting the laser source to have a coherence length such that the sensor has a phase noise less than a phase noise resulting when the sensor is driven by a broadband source.