Sensing device having a large diameter D-shaped optical waveguide

An optical sensor for sensing a measurand, comprising:

• an optical waveguide having an outer cladding and at least one inner core disposed therein which propagates light;
• and
• a D-shaped portion of the optical waveguide having a generally D-shaped cross-section, wherein at least one of polarization or birefringence of the D-shaped portion changes in response to the measurand.

An optical sensor for sensing a measurand, comprising:

• a first D-shaped waveguide having a generally D-shaped cross-section;
• and
• a second D-shaped waveguide having a generally D-shaped cross-section, wherein the first and second D-shaped waveguides are optically coupled together and wherein polarization or birefringence of at least one of the first and second D-shaped waveguides changes in response to the measurand.