Design and Validation of a Single-Head Laser Absorption Spectroscopy Probe using a Fiber Optic Circulator

A compact laser absorption spectroscopy probe has been designed for single-head, two-wavelength-scanning direct absorption temperature measurement. A fiber-optic circulator is used for both the pitch and catch components with a reflector. Cramér-Rao lower bound analysis and Monte Carlo simulations have been conducted to investigate the minimum variance and efficiency of the temperature estimator based on the presented absorption measurement technique using the selected H2O line pairs. A lab flame has been used to validate the designed probe with a reference thermocouple. The measured temperature by the prototype LAS probe and thermocouple agrees well within ±1 % up to 1470 K.