Optical Fiber Specklegram Sensor for Measurement of Force Myography Signals

The development of an optical fiber specklegram sensor for the assessment of force myography signals is reported. The device consists of microbending transducers attached to the user forearm by means of Velcro straps. The muscular stimuli generated in response to hand movements cause the fibers to be mechanically pressed by the deformer structures, resulting in light modulation. The optical signals are acquired and processed according to specklegram analysis, by computing the normalized intensity inner product of speckles for two reference postures. Finally, the average values are correlated to the fingers configurations by means of artificial neural networks. The system was evaluated for a set of 11 static gestures, making it possible to detect subtle variations in the spatial distribution of forces impressed by the forearm flexor and extensor muscles. Moreover, the technique was tested for different subjects, yielding an average accuracy of 89.9% on the estimation of fingers configurations, even with the utilization of a reduced number of transducers.