Fluid concentration detection method and system

Abstract

The invention is applicable to the technical field of fluid measurement, and provides a fluid concentration detection method. The method comprises the following steps: filling a fiber core of a dual-mode hollow-core optical fiber with a fluid containing a to-be-detected substance; inputting the detection laser and the modulated pumping laser into the dual-mode hollow-core optical fiber; when the detection laser enters the dual-mode hollow-core optical fiber, generating a first transmission mode and a second transmission mode of the dual-mode hollow-core optical fiber through excitation; when a to-be-measured substance and the pump laser act to generate a photothermal effect, the phases of the first transmission mode and the second transmission mode are modulated when the first transmission mode and the second transmission mode are transmitted in the dual-mode hollow-core optical fiber; and demodulating a phase modulation difference between the first transmission mode and the second transmission mode to obtain concentration information of the to-be-detected substance. Interference of an external environment on a measurement system can be effectively counteracted, system noise is reduced, a high signal-to-noise ratio is achieved, and the detection sensitivity and the dynamic range of the fluid concentration sensor are improved. 本申请适用于流体测量技术领域，提供了一种流体浓度检测方法，包括：将含待测物质的流体填充至双模空芯光纤的纤芯内；将探测激光和调制后的泵浦激光输入双模空芯光纤中；在探测激光进入双模空芯光纤时，激发生成双模空芯光纤的第一传输模式和第二传输模式；待测物质与泵浦激光作用产生光热效应时，将导致第一传输模式和第二传输模式在双模空芯光纤中传输时的相位被调制；解调第一传输模式和第二传输模式之间的相位调制差，获得待测物质的浓度信息。本申请可以有效抵消外界环境对测量系统的干扰，降低了系统噪声，实现高信噪比，提高了流体浓度传感器的探测灵敏度和动态范围。