In sensors measuring transmission loss caused by slight (miniscule) deflections of an optical fiber or in fiber bends with a radius of curvature well above the fiber diameter (), i.e., in so-called micro-82–88 and macrobend89–107 sensors, respectively, the intensity of the light reaching the receiver is also measured. As in the cases described above, body movements (caused by respiration and heart function, among other things) are a complicating factor since these movements produce micro- and macrobends of fibers with a variable radius of curvature. Thus, along the axis of a bent fiber, the layout of the mode fields continuously changes as the energy radiates; this is seen in the form of light intensity changes at the receiver. The measuring system for micro- and macrobend sensors is distinguished by a simple design for the sensors alone as well as for the associated transceiver modules (light source and photodetector). Nevertheless, due to their relatively low sensitivity, the sensors have to be embedded in a special mat82,83 or cushion,85–88 on which the patient lies during monitoring, or in textiles, such as a vest, T-shirt, or belt, which are worn by the monitored person,89–107 to ensure immediate proximity to the lungs and heart. An example of a microbend sensor system is shown in Fig. 9(a). The sensor mat is constructed by means of two microbenders with MMF passed between them, as shown in Fig. 9(b). The whole setup is covered with a textile material to protect the sensor. A macrobend sensor embedded into an expandable belt is illustrated in Fig. 10 in its most common arrangements, i.e., half-loop (half-oval-form), figure-eight loop, and U-shape.