Optic Fiber Droplet Weighing Sensor Based on Mach-Zehnder Interferometer Cascaded Bowknot Type Taper

A water droplet weight sensor based on Maher-Zehnder interferometer (MZI) cascaded Bowknot Type Taper (BTT) was proposed. MZI consists of two BTTs, and the interval between two BTTs is 2 cm. In this paper, we record the time when the fluid pumped with a peristaltic pump flows through two BTTS, and then drops a droplet into the liquid tube with a needle tubing meanwhile recording the time of the fluid flowing through the two BTTS. All the time can be obtained from the optical spectrum analyzer. Therefore, the volume of the droplet is equal to the velocity of the peristaltic pump multiplied by the cross section area of the liquid tube and the time difference between the two experiments. The weight of the droplet can be easily obtained, as long as we know its density. By measuring the time change of droplet with different weight, this method can be used to determine the droplet weight in the range of 0 similar to 200mg.