Optical probe for measuring light transmission of liquid

An optical probe is for measurement of light transmission of liquid. A tubular housing three equally configured legs defining three arcuately spaced openings in the housing wall. A solid cylindrical member formed of glass or fused silica has a flat transparent end surface and an opposing curved surface silvered to form an internally concave reflector. The cylindrical member is retained in the housing with the transparent end surface adjacent to the openings. A transparent rod member has a flat first end surface and a flat second end surface parallel to the first end surface. The rod member is retained in the housing with the second end surface adjacent to the openings and spaced from the transparent end surface parallel thereto so as to define a cavity therebetween such that, upon immersion of the probe, liquid passes through the openings into the cavity. The first end surface is spaced from the concave reflector so that conjugate focal spots of the concave reflector are located at the first end surface. Two first optical fibers are affixed respectively to the focal spots. Light entering through one optical fiber passes twice through the liquid in the opening while being reflected by the concave reflector into the other optical fiber.