Application of fiber mode mixer in differential optical absorption spectroscopy
光纤模式混合器在差分吸收光谱系统中的应用研究

Differential optical spectroscopy (DOAS) has become an important method for determination of tropospheric trace gases, using the photomultiplier (PMT) as detector. The use of photodiode array (PDA) detectors enhances DOAS system considerably owing to PDA's higher sensitivity and advantage in multi-channel application. When the PMT is simply replaced by PDA, a difference between lamp spectrum and atmosphere spectrum, as will as unwanted standard deviation of residual noise as much as 1.4×10-3 appears after corrected for the pixel response. A fiber mode mixer, based on fiber disturb mode principle was developed and tested. This new device reduces the standard deviation to 3.4×10-4 in field experiments.