Abstract

Light from a single-mode He-Ne laser is coupled into a 100-140-μm step-index fiber. The fiber-optic probe consists of a sterilized piece of similar fiber with one end attached to the instrument with a low- loss wet mateable connector. The other end is highly polished and inserted into a mammalian blood vessel through a hypodermic needle or small incision. Figure 1 shows the optical fiber inserted into the coronary vein of a dog. Light at the laser wavelength is strongly scattered in blood, and this visibility aids the researcher in locating the probe tip in exploring the vascular tree. Only backscattered light from a small region ~0.5 mm in front of the probe tip is returned to the detector. This small sample volume makes the laser Doppler velocimeter (LDV) ideal in the determination of velocity profiles. The probe is inserted in the direction opposite to the flow to ensure that any turbulence created by the probe tip does not affect the measurements appreciably. Indeed the tip can also be used transverse to the flow to determine vessel diameters.

© 1985 Optical Society of America