Active fiber cavity strain sensor with temperature independence

A strain sensor, comprising:

• a laser pump;
• a ring laser cavity coupled to said pump, said cavity comprising:
• a wavelength division multiplexer coupler coupled to said pump;
• an Er-doped, athermal, heavy metal glass, optical fiber coupled to said multiplexer coupler;
• a 3 dB output coupler coupled to said Er-doped fiber;
• and
• a strain sensing, athermal, heavy metal fluoride glass, optical fiber coupled between said multiplexer and 3 dB couplers;
• and
• a multi-mode beat frequency measurement device coupled to said 3 dB output coupler.

A fiber optic sensor, comprising:

• a fiber optic laser cavity;
• means for pumping said cavity;
• and
• a fiber optic gain portion;
• wherein said cavity, said means for pumping, and said gain portion are operatively interconnected to produce a plurality of laser beat frequencies in said cavity;
• and
• wherein said sensor further comprises means for detecting frequency change, induced by mechanical straining of at least a portion of said cavity, of a preselected one of said beat frequencies.