Fibre optic gyroscope

For sensing rotation, we can use fibre optic gyroscopes. These gyroscopes have vital and important role in military applications, especially in aircrafts and missiles. Here light is sent in opposite directions through a loop of single mode fibre. If the loop is stable, perfect and still, the light traveling in opposite directions will travel equal distance in one complete cycle. If the fibre loop has rotated, the two beams traveling in opposite directions travel different path lengths, leading to a phase difference. Interferometric techniques can be employed to measure this phase difference.