Optical attenuation by periodic microdistortions of a sensor fiber

The attenuation of optical power in a graded-index multimode fiber subjected to periodic microdistortions has been measured. The noncommunication fiber (designated the sensor fiber) had a small numerical aperture and a large core diameter, resulting in a large coupling wavelength and an enhanced sensitivity to microdistortion forces. The linewidth of the fundamental attenuation peak is in excellent agreement with that predicted by theory without the need to introduce a correlation length. The amplitude and force dependence of the attenuation measured at the fundamental peak is also in excellent agreement with theory. The inferred distortion force versus distortion amplitude curve is a straight line, as predicted by elasticity theory.