Chemical detection system of optical base

PROBLEM TO BE SOLVED: To provide a small-sized and strong multiple spectrum sensor system capable of sensing a chemical species in a fluid on the spot. SOLUTION: A sampling means 12 sampling a fluid and having light input and output ports 18, 20, the light source connected to the light input port and forming electromagnetic radiation having a wavelength absorbed by one of predetermined chemical species and a monolithic sensor structure constituted of a plurality of radiation detectors are provided. The respective radiation detectors 26 are coupled with the light output port 20 of the sampling means 12 and respond to the wavelength band containing a wavelength absorbed by a chemical species in order to determine the electromagnetic radiation quantity in the wavelength band transmitted through the sampled part of the fluid. The outputs of the radiation detectors 26 are further processed by a signal processor 32. An input filter 24 is provided in the radiation detectors 26 and the radiation detectors 26 are accumulated on a substrate along with an amplifier 28 or the like.