Time-domain optical sensing - Electronics Letters

sensitive paper (Kodak Panalure) with the capillary at the centre. (i) and (ii) in Fig. 3 show the response of a water-filled, uncoated capillary under TE and TM illumination, adjusted to strike a broad range of angles and to highhght the region of the capillary response corresponding to reflections from the internal surface below the critical angle (30a to 90" in Fig. 3). As expected, TE reflectivity is greater in this region. The fringes (-30" to 30" in Fig. 3) result from the interference of rays that travel different optical paths through the capillary, but emerge at the same angle 141.