SYSTEM AND METHOD FOR PASSIVE OPTICAL MONITORING OF THE CONCENTRATION OF MULTIPLE GASES AND/OR MULTIPLE PARAMETERS AT MULTIPLE POINTS

The present invention relates to a system and method for passive optical monitoring of the concentration of multiple gases and/or multiple parameters at multiple points for obtaining and monitoring the methane concentration in offshore platforms and onshore structures, and also in the fields of mining, landfills and other industrial sectors. The system consists in the sending, by a remote fibre optic unit, of a frequency-modulated light pulse (intra-pulse modulation) that is optically selected and directed at optical splitters and delay lines for various measurement points of interest, giving rise to multiple signals that interact with the methane gas in reflective sensors, that is, sensors that reflect light, returning to the remote unit a time signal from N point sensors, which is detected by a single optical receiver and the time signals of which are analysed individually by calculating the fast Fourier transform (FFT). The FFT signal thus obtained contains an amplitude A0 at the zero frequency or DC component, f0, an amplitude A1 at the same modulation frequency as the laser, f1, and an amplitude A2 at twice the original laser frequency, f2 = 2 x f1. In this way, the system makes it possible to obtain the concentrations (C) from the N sensors on the basis of the amplitudes A0, A1 and A2, by calculating the mean (M) between log(A2/A0) and log(A2/A1), that is, M = ½ × [log(A2/A0) + log(A2/A1)], and a calibration curve, where M is invariant with respect to the optical loss of the fibre optic links and depends solely on the concentration. L'invention, intitulée « Système et procédé de surveillance optique passive de concentration de gaz multiples, de paramètres multiples au niveau de points multiples », vise à obtenir et surveiller la concentration de méthane dans des plateformes offshore et des structures côtières, ainsi que dans les secteurs de l'industrie minière, de l'enfouissement sanitaire et d'autres domaines industriels. Le fonctionnement du système consiste à envoyer, au moyen d'une unité distante à fibre optique, une impulsion de lumière modulée en fréquence (modulation intra-impulsion) qui est optiquement sélectionnée et dirigée vers des diviseurs optiques et des lignes de retard pour divers points de mesure d'intérêt, donnant lieu à de multiples signaux qui interagissent avec le méthane gazeux dans des capteurs réflexifs, c'est-à-dire des capteurs qui reflètent la lumière, un signal temporel de N capteurs ponctuels étant envoyé en retour vers l