These fibers can be inserted into the combustion chambers of internal combustion cylinders or turbine engines. In this way optical signal can be brought outside for spectral analysis.
Fuel constituents, contaminants, combustion products and combustion chemistry can be monitored in order to control fuel mixture, flow and timing.
Sapphire fibers can even be used in the fluorine plasmas used in semiconductor processing.
Other applications for this type of fibers are laser delivery for medical applications.
The Er:YAG laser produces a beam of wavelength at 2.94µm. This wavelength is very useful for certain types of medical and dental surgery.
Sapphire not only transmits this wavelength well, but have a laser damage threshold over 1200 Joules/cm², and is also biologically inert and autoclavable.