1. Non-intrusive technique:
Using a thermocouple or a thermometer usually changes the actual value of the temperature while coming to steady state.
Optical techniques are non-intrusive and the measured value do not deviate from the actual value.
Light travels at very high speed. So it's possible to make real time high speed
measurements and only limited by instrumentation capability.
3. Good hardware capabilities available:
Rapid improvement of data storage and high speed computing enables effective use of this techniques. The development of
this techniques were mostly limited by this in previuos days.
There are of course many more advantages to it.