Optical Fibers on Medical Instrumentation: A Review

Technology

An optical fiber by itself is not a sensor. A set of complementary technologies must be used in conjunction with optical fibers. Excluding few applications (Bilro et al., 2011; Correia et al., 2013; Morim, 2008) that belong to the category of intrinsic sensors, the optical fibers are often used exclusively as auxiliary elements for providing/collecting light into/from direct-in-contact sensorial structures (e.g., belonging to the extrinsic category). The optical detection can be provided by two ways: by direct transmission with an optical source aligned on a given extremity and the optical detector on the other extremity; and by reflection, with both the optical source and detectors are in the same extremity of the optical fiber. In this second approach, an optical circulator must be used to separate the generated and reflected optical beam into/from the optical source. The Figure 1 illustrates these two approaches. In the example (a), the light attenuates along the optical fiber, whereas in the example (b), the optical fiber is used as a simple light conduction element.

Figure 1.

Concept illustration behind the (a) direct and (b) reflect detection