A nitrogen oxides (NOx) and sulfur dioxide (SO2) gas analyzer using deep ultraviolet (DUV) and violet light- emitting diodes (LEDs) is developed. The LEDs with wavelengths of 280 nm and 400 nm were alternately turned on to detect SO2 and nitrogen dioxide (NO2) absorption. Nitric oxide (NO) was converted to NO2 with an ozonizer. In order to reduce water interference caused by water adsorption onto an inner surface of a gas ow cell, collimating optics reducing re ected lights were designed. As a result, less than 1% by full scale (%F.S.) of uctuation, 2%F.S. of drift and 0.5%F.S. of water interference were achieved in 0-50 ppm concentration range. Conversion efficiency from NO to NO2 was over 95%.
A method to increase the multiplex capacity of an arrayed waveguide grating (AWG) based interrogator is proposed that makes use of the spectral recurring feature of AWG due to its free spectral range. Using a single AWG, interrogation for two different wavelength regions of 1310nm and 1550nm was performed with a high performance of the standard deviation of the level of sub-pico-meter for 2nm dynamic range. The proposed method is very helpful to reduce the cost of the AWG interrogator.