The operation of an optical fiber vibration sensor using two fiber Bragg gr
atings (FBGs) and incoherent light has been demonstrated, based on the inte
nsity-modulation method. One FBG is used to make a narrow-band incoherent l
ight source from a broad-band light source and the other is used for sensin
g the vibration of a solid. Stable and linear operation of the sensor is re
alized without optical isolators and fusion splicing. The developed sensor
is expected to be temperature insensitive if the temperatures of the two FB
Gs are kept same during the operation.