ABSTRACT
Fiber-optic techniques for chemical analysis offer several advantages. Probes can be installed in situ to monitor the composition of chemical process streams in real time. One probe sends a highly collimated light across the sample, and the second collects the light and focuses it back onto a single fiber. Upon exiting the fiber, the rays of light impinge upon the sample, which gives off a characteristic fluorescent emission. Light travels to the sampling probe via one fiber-optics cable and returns to the instrument via a second. The absorption characteristics of silica limit practical fibers to a spectral range of about 200 to 2200 nm. All near-infrared (NIR) on-line instruments use fiber-optical bundles to interface with the process. The use of fiber bundles permits high energy throughput, which ensures accurate and precise NIR measurements. Designed in single-strand fiber and fiber bundle configurations, the wand probe employs a mirrored tip to reflect from the sending fiber(s) to the receiving fiber(s).
