“…(1)(2)(3) Optical fiber sensing for RI measurement has been widely implemented because of its advantages of anti-electromagnetic interference, strong remote monitoring ability, and low price. (4)(5)(6)(7) Similarly, high-precision liquid level sensing is of considerable significance in chemical industry, oil storage, public water supply, and so forth. By monitoring the changes in physical quantities related to liquid level information, the remote monitoring and control of liquid level can be achieved.…”