Sources, fiber-optic chemical sensors

Figure 3. First fiber optic chemical sensor (from ref. [17] used for sensing oxygen). Alos shown is a cross-sedction of the fiber bundle used. 6 light source 9 photodectectors 16 chemically sensitive layer.

The basic design of a fiber-optic chemical sensor system is shown in Fig. 1. The fiber-optic chemical sensor s main components are (a) a light source, (b) optical fibers fo both transmit the light and act as the substrate for (c) the sensing material, and (d) a detector to measure the output light signal. Usually computers or microprocessors control the fiber-optic chemical sensor instrumentation and are employed to analyze the output signals. 

The light sources used for fiber-optic chemical sensors should provide sufficient light intensity within the sensor... 

Typical fiber-optic chemical sensors for in vivo monitoring are constructed from optical fibers that are connected to an external compact unit containing the light source and the detector, as shown in Fig. 18. The optical fiber s distal end is inserted into the patient through a catheter. 

A variety of transducer configurations that has been employed in photometric sensor devices fall into two sensor types extrinsic sensors and intrinsic sensors. While in the former sensor type the optical fiber merely acts as a light guide, conveying the optical information between the optical source and the chemical transducer and between the chemical transducer and the detector, in the latter sensor type the optical fiber, probably in some modified form, would become a part of the transducer. 

Fiberoptic sensors can be used to measure PAHs in situ A xenon lamp is a common excitation source when connected to optical fiber to excite a sample remotely and induce fluorescence. The fluorescence light emitted is collected by another optical fiber and transmitted to a photomultiplier detector. Sensors are chemically modified to enhance selectivity and sensitivity. (3-cyclodextrins and immunochemical reagents on optical fiber probes can selectively determine individual PAHs but with some crossreactivity. Fluorescence probes such as perylene can be imbedded in polymers affixed to the end of the probe. 

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