Two-Channel Optoelectronic Sensor Employing Cavity Enhanced Absorption Spectroscopy

In the paper, a description of two-channel of optoelectronic sensor basing on cavity enhanced absorption spectroscopy is presented. In contrast to the typical cavity enhanced absorption spectroscopy systems, here a special optical system is applied. It provides possibility to direct more than one beam of laser radiation into a cavity. Thus, special lasers controller system and photoreceiver were developed as well. The setup includes two pulsed laser diodes. The optical signals from the lasers are registered with one special constructed photoreceiver, which is characterized by wide range of the detected wavelengths. Moreover, there was applied time division multiplexing technique, well-known in the telecommunication systems. Every laser is assigned to the suitable channel - the strictly determined temporary window. In this window, the signal from the exits of the optical cavity is registered. In the system, optical signal from many laser sources can be measured and value of absorption coefficient at a few different wavelengths can be determined parallel. Typical cavity enhanced absorption spectroscopy system is designed to measure only one gas concentration, while the developed setup provides possibility to detect a trace concentration of two gases at the same time.