Detection of optical signals in selected sensing applications

The paper presents some aspects of approach to construct an optical detection system for laser absorption sensing. These aspects concern a designing procedure of the system, starting with a photodetector, preamplifier, and ending with a signal processing. There is also discussed a project of integrated preamplifier which can be applied in Cavity Enhanced Absorption Spectroscopy (CEAS). In the preamplifier, boxcar method was implemented using integrated circuit (IC) of switched integrator and a special synchronous block. Taking into account an idea of CEAS operation, selected methods of the exponential signal analyzing are described and tested. The main task of the methods is to determine decay time of this signal. The results of these tests make it possible to define some virtues of the designed boxcar technique that could be useful in CEAS sensing instrument.