Influence of stray light in spectrometers on the accuracy of a fiber-optic temperature sensor

Subject of study. This study investigates parasitic radiation caused by the reflection and scattering of incident radiation from the internal surfaces and components of the Hamamatsu C12880MA mini-spectrometer. Aim of study. The aim of the study is to reduce measurement errors in a fiber-optic temperature sensor (FOTS) caused by radiation scattering outside the working spectral range of its spectrometers through the introduction of an infrared filter into the pyrometer optical system. Method. Optical radiation from an SI10-300 lamp at temperatures ranging from 1200 to 2300 K was recorded with and without an SZS25 colored-glass filter in the optical sensor. The experimental data were compared with the spectral characteristics of blackbody radiation. Temperature was determined using the spectral pyrometry method in the 600–700 nm wavelength range. Main results. The presence of a parasitic signal in the 300–500 nm wavelength range, caused by stray light with wavelengths greater than 800 nm inside the device, was experimentally confirmed. A method for determining distortions in the spectrometer response was developed to analyze the contributions of stray light in different spectral regions. The magnitudes of parasitic signals in different sensor channels were compared. Introducing an infrared filter into the optical system substantially reduced parasitic radiation at lamp temperatures of 1200–1600 K and decreased the measurement error from 8% to 1.5%. Practical significance. The results of this study can be used to improve the accuracy of spectral FOTS systems.