Weak reflection terahertz fiber optic devices for distributed sensing applications

A fiber optic sensor device for distributed measurements of stress, strain and temperature, comprising:

• an optical fiber detection arm comprising an inner core extending along a length of the optical fiber detection arm, an outer cladding surrounding the inner core and extending along a length of the optical fiber detection arm, and at least one reflector structure formed within said inner core,
• said reflector structure comprising first and second spectral reflectors having a terahertz range pitch spacing (Δz) between about 10 terahertz and 100 gigahertz,
• each of said spectral reflectors having an ultra-weak spectral reflection of <−50 dB
• said optical fiber detection arm terminated with an anti-reflection cut;
• and
• a narrow bandwidth interrogation system coupled to said optical fiber,
• said interrogation system comprising a narrowband tunable laser source having a tunable bandwidth of 100 gigahertz or less,
• said interrogation system interrogating said optical fiber detection arm to detect changes in reflections and interference patterns caused by physical changes in said optical fiber.

A fiber optic shape/position sensing device based on ultra-weak, terahertz-range reflector structures comprising:

• a plurality of fiber optic sensor devices extending in parallel, adjacent relation to form a shape-sensing bundle,
• each of said fiber optic sensor devices comprising an optical fiber detection arm an inner core extending along a length of the optical fiber detection arm, an outer cladding surrounding the inner core and extending along the length of the optical fiber detection arm, and at least one reflector structure formed within said inner core, said reflector structure comprising first and second spectral reflectors having a terahertz range pitch spacing (Δz) between about 10 terahertz and 100 gigahertz, each of said spectral reflectors having an ultra-weak spectral reflection of <−50 dB said optical fiber detection arm terminated with an anti-reflection cut, and further comprising a narrow bandwidth interrogation system coupled to said optical fiber, said interrogation system comprising a narrowband tunable laser source having a tunable bandwidth of 100 gigahertz or less, said interrogation device interrogating said detection arm to detect changes in reflections and interference patterns caused by physical strain changes in said optical fiber and to output a strain profile for said optical fiber;
• and
• a shape-sensing unit coupled to each of said plurality of fiber optic sensing devices, said shape sensing unit receiving said strain profile from each of said plurality of fiber optic sensing devices and providing a three-dimensional shape profile of said shape-sensing bundle.