An IFPI sensor contains two mirrors separated by a
distance within a fiber core. The earliest IFPI sensor
probably is the spliced TiO2 thin film coated fiber IFPI
sensor. In this sensor internal mirror is introduced in fiber
by thin film deposition on the cleaved fiber end followed by
fusion splicing as shown in Figure 13. Several other
methods are also used to produce internal mirror, such as
using vacuum deposition, magnetron sputtering, or e-beam
evaporation [19].