Sensitivity-Enhanced Flow Rate Sensor Based on Vernier Effect With a Virtual Reference Cell

A novel scheme for the measurement of an ultralow flow rate based on a fiber Fabry–Perot interferometer (FPI) and sensitivity-enhanced Vernier effect is proposed. The impact of water at different flow rates varies the cavity length of the sensor, resulting in a change of the free spectrum range (FSR) of the interferometric spectrum. The theoretical relation between the FSR and flow rate has been established by numerical simulation. The sensitivity can be further enhanced via the Vernier effect with a virtual reference cell and experimentally verified in the flow rate range of 0– $80\,\mu \text{m}$ /s. The proposed interferometric sensor with modified Vernier effect is used for ultralow flow rate measurements for the first time, which shows the potential for applications in microfluidic technology and biochemical reaction.