Active fiber cavity strain sensor with temperature independence

摘要

A strain sensor system formed from a laser cavity where changes in length of the cavity are used to measure strain. The cavity can include a passive optical fiber strain sensing section and/or an active doped optical fiber section that lases when pumped by a laser pump. The cavity can be a ring or linear cavity with or without mode locking. The light oscillating in the cavity sets up multiple oscillation modes. The multiple modes create beat modes or frequencies. The measured frequency difference between beat mode frequencies is inversely proportional to the length of the cavity. The measured frequency change in one of the mode frequencies or one of the beat frequencies is proportional to the absolute strain on the fiber. A heavy metal fluoride glass sensing section makes the sensor temperature insensitive.