Abstract

In this paper, we present a fiber sensing technique which detects the mean absolute speckle intensity variation between the up-dated and the reference speckle patterns, by which the mean absolute intensity variation of the fiber output due to external perturbation gives rise to the change of the modal phase differences. This system can be used for displacement, temperature, pressure, and acoustic wave sensing in an environment where other conventional sensing techniques are difficult to be employed. We have shown that the proposed system is highly sensitive to the modal phase variation from a multimode sensing fiber and the operation of the sensing system is rather simple. One of the major advantages of the proposed system is that it can perform a real-time fast response dynamic measurement by using the off-the-shelf electronic hardware. From our experimental demonstration we have shown that this technique can be used for sub-micro displacement sensing, with a measurement sensitivity as high as 0.1 μm. By updating the reference pattern, the dynamic range of the proposed system can be extended. Experiment for temperature measurement is also provided, in which we have shown that the sensitivity can be as high as 0.1 °C.

© 1993 Optical Society of America