Measuring structural vibrations with a multimode fiber optical sensor

The possibility of measuring amplitude and frequency of structural vibrations using a multimode optical fiber is demonstrated. By detecting and analyzing the variations in the output signal speckle pattern it is possible to detect vibrations and their parameters. A working experimental model has been built and tested. Components used for this system are cheap and widely available: a CCD array (a simple web-cam), a common laser as a light source, a length of multimode optical fiber, and a computer where the data analysis is performed. Measurements have been made which show good agreement with actual values for the frequency parameter, and promising results were achieved with the amplitude measurements although they require some adaptation of the experimental model. This type of sensor system could find use in all areas of vibration sensing. It is a low cost and lightweight system and therefore extremely interesting for integration in smart structures.