Research on fiber fabry-pérot salt concentration sensor for cooling pipelines of thermal power plants

This paper reports a fiber Fabry-Pérot (FP) salt concentration sensor fabricated via femtosecond laser micromachining, targeting real-time salinity monitoring of cooling pipelines in thermal power plants to support automatic water replenishment control. Experimental results reveal that the FP cavity achieves optimal reflectivity at a cavity depth of 66.95 μm and a cavity width of 10.98 μm. As the refractive index of medium filling the FP cavity rises, the resonant spectral peak undergoes a continuous red shift. After systematic optimization of femtosecond laser machining parameters, the optimal laser fluence is determined as 7.96 mJ/cm 2 with an ablating speed of 0.22 mm/s. Within the salt concentration range of 10%∼22%, the fabricated sensor delivers an average sensitivity of 1.90 nm/% and a coefficient of determination R 2 = 0.9993. Experimental measurements are highly consistent with numerical simulation results. The proposed femtosecond laser machining scheme exhibits great potential for mass production of fiber FP salinity sensors.