P3 - Detection of Optical Signal in the Multispectrac Sensor Employing Cavity Enhanced Absorption Spectroscopy

SENSOR+TEST Conferences 2011
2011-06-07 - 2011-06-09
Proceedings OPTO 2011
OP - Poster Session
R. Medrzycki, J. Wojtas - Military University of Techno¬logy, Warsaw (Poland)
117 - 122


In the paper, a preliminary experiments and analyses concerning multi-spectral optoelectronic sensor applying cavity enhanced absorption spectroscopy (CEAS) are described. The main element of this sensor is special photoreceiver system, which is characterized by wide range of the detected wavelengths. Thanks to this, optical signal from many lasers can be measured using one photoreceiver. Moreover, in one cavity, a value of absorption coefficient at a few different wavelengths can be determined parallel.

Typical CEAS system designed for measurements of the trace gases concentration consists of a pulse radiation source, optical cavity, photoreceiver, and a signal processing system. In the experimental setup two lasers and two optical channels were used. The setup makes it possible to detect a trace concentration of two gases simultaneously. Every laser is assigned to the strictly determined temporary window. In this window, the signal from the exits of the optical cavity is registered.

To appropriate developing photoreceiver system, determination of signal-to-noise ratio (SNR) is very important. Due to high value of SNR of the optical cavity, signal-to-noise ratio of an electronic circuit is the most important parameter in the CEAS sensors. Because of high cavity mirrors reflectivity coefficients small number of photons reach a photodetector. The presented setup is of greatest interest with respect to the possible applications. For example, it can be used in ambience monitoring, luggage monitoring in ports, on airports, entry points, as well as in strategic objects and rooms also in undertakings connected with the counteraction to terrorist attacks.