傅里叶变换红外光谱法被广泛应用于融石英Si―OH含量测量中。然而，低Si―OH含量下水吸收峰的干扰和高Si―OH含量下吸收峰饱和限制了测量范围。使用傅里叶变换红外光谱法测量不同Si―OH含量和厚度的熔石英样品在2500 cm^-1~5000 cm^-1波段的透过率，消除水分子吸收带对3673 cm^-1波数Si―OH吸收峰的干扰；分别使用3673 cm^-1和4522 cm^-1峰对不同样品的Si―OH含量、均方根误差，以及3673 cm^-1和4522 cm^-1峰的检测限进行计算。结合实验结果和比尔定律，建立Si―OH浓度、样品厚度、测量透过率误差与测量浓度误差之间的关联模型。根据模型，在2 mm厚度时使用3673 cm^-1吸收峰测量Si―OH含量小于8.17×10^-4的样品，使用4522 cm^-1弱吸收峰测量Si―OH含量大于8.17×10^-4的样品，可优化测量精度和扩大测量动态范围，实现2 mm厚度时熔石英(0.4~10000)×10^-6大范围Si―OH含量测量。

Fourier transform infrared (FTIR) spectroscopy Si―OH group is widely used in Si―OH content meas-urement of fused silica optics. However, the measurement accuracy is influenced by water molecular absorption bands in low Si―OH content samples and absorption saturation in high Si―OH content samples, leading to lim-ited measurement range. FTIR spectroscopy is employed to measure 2500~5000 cm^-1transmittance spectra of fused silica samples with different OH contents and thicknesses. The interference of water molecular absorption band to 3673 cm^-1is eliminated. Then Si―OH contents, corresponding measurement errors and limits of detec-tion at 3673 cm^-1and 4522 cm^-1bands are calculated. Based on the experimental results and Beer’s law, a model to correlate Si―OH content, sample thickness, measurement error of transmittance, and measurement error of Si―OH content is established. From this model, by using 3673 cm^-1band for fused silica samples with Si―OH content less than 8.17×10^-4and 4522 cm^-1band for samples with Si―OH content more than 8.17×10^-4to meas-ure the Si―OH content, a dynamic range from 0.4×10^-6to 10^-2Si―OH can be achieved with optimized accuracy for fused silica samples with 2 mm thickness.