In this work, we report fiber Bragg gratings (FBGs) embedded in silicone tubes for joint movement monitoring. We integrate the sensors on finger guard bands and worn on a mechanical finger setup for finger joint bending monitoring. We demonstrate the shift of the central wavelength of the FBG of about 0.45 nm for 80° bending, with a sensitivity of 5.6±0.5pm/°. By integrating the sensor on the finger, arm, and knee with guard bands in sinuous-shape, we monitor the bending of the joint, with the ability to distinguish the joint motion. The proposed sensor has a potential for application in Stroke rehabilitation.

Using the power flow equation, we have examined the mode coupling caused by intrinsic perturbation effects of the step index plastic optical fiber. A numerical solution has been obtained by the explicit finite difference method. Results show the state of mode coupling along the fiber. They indicate that the equilibrium mode distribution is achieved at much shorter lengths compared to the case with glass fibers.

A method is proposed for predicting the evolution of the power distribution along graded-index plastic optical fibers. This method is verified against our recently reported measurements. The strong influence of mode coupling on the power distribution is demonstrated on a specific graded-index plastic fiber to illustrate the influence of mode coupling in applications, such as data transmission, power delivery, and sensing systems.