Applications of FBG Sensors 493 sensitivity are such that they provide sufficient information for bending, tem- perature, and strain data to be determined uniquely. Further characteristics of LPGs for sensing may be found in reference [99]. 10.4 APPLICATIONS OF FBG SENSORS From the preceding discussions, it is clear that the FBG and LPG are excel- lent devices for a variety of sensing applications. The small size and in-line nature make them ideal for a large number of applications. Here we consider some of the applications of FBGs. 10.4.1 Biomedical Sensing: Hydrostatic Pressure Sensing in Medicine Applications in biomedical sensing have steadily increased, from simple tem- perature measurement through in vitro [100], to in vivo distributed temperature sensing [101], to, more recently, the measurement of hydrostatic pressure in spi- nal fluids for the treatment of lumbar deformities and injuries [102]. In the latter application, an FBG is inserted into the viscoelastic shell between vertebrae through a thin hypodermic needle, as shown in Fig. 10.46. A standard strain