Fiber optic probe and method for detecting optically active materials

An optical probe for use in determining the presence of an optically active constituent in a fluid medium, comprising:

• a) a fluid tight housing immersible in the fluid medium, said housing having a chamber therein for receiving said medium,
• b) light input means for transmitting incident planar polarized light along a path from a source thereof to one end of said chamber for a first pass through said medium to impart a first optical rotation to the incident light attributable to the optically active constituent of said medium,
• c) reflective means in the path of said light at the opposite end of said chamber for reflecting the incident light back along a reverse path to said chamber for a second pass through said medium,
• d) means plate between the reflective means and the chamber and in the path of the light for altering the first optical rotation before said second pass through said medium so as to achieve a second optical rotation during said second pass that is attributable to said optically active constituent and is additive to said first optical rotation, and
• e) light collecting means for collecting the reflected light.

A method of determining the presence of an optically active constituent in a fluid medium comprising the steps of:

• a) directing plane polarized light in a first pass through the fluid medium in a first direction to induce a first optical rotation of the plane of polarization attributable to the optically active constituent,
• b) altering the first optical rotation of the light following said first pass through said fluid medium by retarding one component of said light one-half wave with respect to a perpendicular component of said light,
• c) reflecting the light following said first pass for a second pass through said medium, said second pass following the altering of the first optical rotation to achieve a second optical rotation during the second pass attributable to the optically active constituent and combinable with the first optical rotation to yield a detectable optical effect, and
• d) collecting the light from the second pass for analysis.

In an optical probe for use in determining the presence of an optically active constituent that produces circular birefringence, in a fluid medium, the combination of a source of light;

• first and second optical input fibers for transmitting light from said source through said fluid medium for a first pass;
• means for imparting plane polarization to the light transmitted by said fibers before passing through said fluid;
• a wave retardation device to retard one component of said light one half wavelength with respect to a perpendicular component of said light after said first pass but before a second pass;
• a reflector for reflecting said light after said first pass to direct said light through said fluid for said second pass;
• first and second optical output fibers oriented relative to the respective first and second light input fibers to receive therefrom light that traverses said fluid medium after said second pass and transmit such light along a path;
• and first and second polarized analyzer members for selecting for analysis respective first and second polarized light components from the light received by said output fibers.