We demonstrate a high temperature sensor by using an intrinsic photonic crystal fiber (PCF) based Mach-Zehnder
interferometer. Air hole collapsed regions inside the PCF act as coupler between the core and cladding modes which
form the two arms of the interferometer. The temperature measurements are obtained by measuring the shift in the peaks
of the interference signal. The experiments confirm the reliability, repeatability and hysteresis. The small amount of
hysteresis and deviation in the repeated experiments are within the experimental errors.
Fiber Bragg gratings (FBGs) have been frequently employed for the strain and temperature measurement in many
distributed sensor systems. For multipoint measurements with a very large number of measurement points such as smart
structure applications, the multiplexing of FBG sensors is one of the most detrimental techniques to reduce both
installation and operation cost for multipoint measurements. We proposed a new method of increasing the multiplexing
capability of a multipoint FBG sensor system without increasing the system complexity by providing a unique spectral
response to each FBG at a different location as an identification tag. FBG elements were fabricated to furnish reflectance
spectrums to have a multi peaked structure. The number of sensors in the present spectral tag method increases as a
multiple power of N, the number of spectral code. The free spectral range available for spanning the parameter to be
measured is as wide as a substantial fraction of the whole spectral bandwidth of the system.