The invention discloses a transmission-type
optical fiber liquid level sensor with an irregular core structure. The transmission-type
optical fiber liquid level sensor comprises a
wideband light source, a sensing head and an
optical fiber spectrum analyzer, wherein the sensing head is formed by
welding a section thin core single mode
fiber onto the middle of common single mode
fiber, during measurement, one part of the thin core single mode
fiber is positioned on a liquid level, and the other part of the thin core single mode fiber is positioned below liquid level. The common single mode fiber receives light coming from a
wideband light source and is coupled to the thin core single mode fiber, so that the light is transmitted inside the thin core single mode fiber in a form of a mandrel and a
cladding mode so a to form an interferometer similar to Mach-Zehnder interferometer. Light of the two parts interferes mutually and then is coupled into the common single mode fiber again and finally led into an optical fiber
spectrum analyzer. By measuring drift amount of wave length of the characteristic peak in transmitted spectrum, the liquid-level variation can be calculated. The transmission-type optical fiber
liquid level sensor has a compact structure, has the benefits of simplicity in preparation, high measuring accuracy, wide measuring range, safety,
explosion protection and the like, and is particularly suitable for precision measurement to liquid level of inflammable liquid.