Abstract: In order to complete the real-time measurement of long-distance multi-point gas concentration，the writer designed the structure of a reflection-type spectral absorption fiber sensor network. The laser light source was modulated by the wavelength modulation spectrum，and the wavelength of the light source was adjusted with the amplitude and offset of the triangular wave，to ensure that the spectral scanning center value was the same as the methane gas absorption peak. At the receiving end，in order to effectively collect the photoelectric signal，a multi-point high-speed signal acquisition software method was designed in this paper ，the influence of its modulation depth was analyzed at the same time. Experimental results showed that the software acquisition algorithm and the appropriate modulation depth could meet the precision requirements of multi-point acquisition of optical fiber gas sensor in engineering.

Key words: optical fiber sensor, quasi-distributed, multi-point acquisition, modulation depth