Optical fibers near-infrared

We have previously shown that a fiber optic equipped near-infrared spectrophotometer (NIR) can be used to measure the composition of a blend of polypropylene with recycled polyethylene. In this current work, we show the results of monitoring color in-line, rather than composition, by using the visible part of the spectrum measured from the same spectrophotometer (which we now term a Vis-NIR instrument). 

Chan K., Ito H., Inaba H., Humio H., Remote sensing system for near-infrared differential absorption of methane gas using low-loss optical fiber link. Appl. Optics 1984 23 3415. 

Inaba H., Chan K., Ito H., All-optical remote gas sensor system over a 20 km range based on low-loss optical fibers in the near infrared region, Proc. SPIE-Int. Soc. Opt. Eng. 1984 514 211. 

Miniaturized chemical analysis systems have been developed for most macroscopic counterparts (Dittrich et al. 2006). The availability of optical fibers, light sources, and detectors in the visible UV and near-infrared (NIR) wavelengths makes it possible to integrate spectroscopic measurements in microreactors (Lobbecke et al. 2005). Fourier transform infrared spectroscopy (FTIR) is an efficient, broadly applicable... 

Fiber glass-reinforced plastic tanks, 24 299 Fiber grating, 11 150-151 Fiber length (FL), 18 148 Fiber manufacture, sodium bisulfite in, 23 673 Fiber-matrix bonding, 26 771-772 Fiber modification, chemical, 16 14 Fibernodes, 11 595 Fiber-optic probes, 16 524 Fiber optics, 11 128-162, 15 469 attenuation in, 11 132-133 dispersion in, 11 134-135 fiber drawing in, 11 141-145 fiber strength in, 11 141-145 history of, 11 128-131 inside processes for, 11 136-140 near-infrared, 23 141 optical amplifiers with, 11 145-146 optical fiber fabrication for,... 

Infrared spectra, of fats and oils, 10 823 Infrared spectral region, 19 564 Infrared spectroscopy, 14 224-243 23 136-143. See also Chromatography-infrared spectroscopy Far- infrared spectroscopy ir-selective surfaces Ir (infrared) spectroscopy Near- infrared spectroscopy Thermal analysis-infrared spectroscopy applications of, 14 239-240 23 140-141 in composition measurements, 20 682 in fiber optic fabrication, 11 138 industrial applications of, 14 240 instrumentation in, 14 225-228 23 137-138... 

T. Okazaki, T. Imasaka, and N. Ishibashi, Optical-fiber sensor based on the second-harmonic emission of a near-infrared semiconductor laser as light source, Anal Chim Acta 209, 327-331 (1988). 

M. Daneshvar, G. A. Casay, M. Lipowska, G. Patonay, and L. Strekowski, Investigation of a near-infrared fiber-optic immunosensor, SPIE—The International Society for Optical Engineering Chemical, Biochemical, and Environmental Fiber Sensors V 2063, 128-138(1993). 

Simply stated, fiber-optic cable allows for the transfer of light from one point to another withont going in a straight line, and as such their use in process analytical apphcations is highly seductive. In a likely near-infrared process application there may be multiple sample stream take-offs, each with different sample characteristics, located in positions spread around a process unit, with the only apparently convenient analyzer location some distance away. 

C. Coffey, A. Predoehl, D.S. Walker, Dryer effluent monitoring in a chemical pilot plant via fiber-optic near-infrared spectroscopy, Appl. Spectrosc., 52(5), 717-724 (1998). 

S.C. Harris and D.S. Walker, Quantitative real-time monitoring of dryer effluent using fiber optic near-infrared spectroscopy, J. Pharm. Sci., 89(9), 1180-1186 (2000). 

S.2.2.2 ICLS Example 2 This example discusses the determination of sodium hydroxide (caustic) concentration in an aqueous sample containing sodium hydroxide and a salt using NIR spearoscopy. An example of this problem in a chemical process occurs in process scrubbers where CO, is converted to Na,CO and H,S is converted to Na,S in the presence of caustic. Although caustic and salts have no distinct bands in the NIR, it has been demonstrated that they perturb the shape of the water bands (Watson and Baughman, 1984 Phelan et al., 1989)-Near-infrared spectroscopy is therefore a viable measurement technique. This method also has ad tages as an analytical technique for process analysis because of the stability of the instrumentation and the ability to use fiber-optic probes to multiplex tlie interferometers and Icx ate them rcm< >tely from the processes. 

Petrov, G. L, Yakovlev, V. V., and Minkovski, N. I. 2003. Near-infrared continuum generation of femtosecond and picosecond pulses in doped optical fibers. Appl. Phys. B 77 219-25. 

Coffey, C. Cooley, B.E., Jr Walker, D.S., Real time quantitation of a chemical reaction by fiber optic near-infrared spectroscopy Anal. Chim. Acta 1999, 395, 335-341. 

Figure 13.10 Photograph showing fiber-optic interface for collecting noninvasive near-infrared spectra from a rat skin model.

A miniaturized Fourier transform spectrometer for near-infrared measurements (FTIR, 2500-8330 nm) was developed at the Forschungszentrum Karlsruhe [120], Near-infrared measurements give information, for example, about the oil, water and protein content of liquids or solids. The dimensions of the detector chip are 11.5 x 9.4 mm, the device is essentially a miniaturized Michelson interferometer and it consists of a micro optical bench with beamsplitter, ball lenses, mirrors and the detector chip. The light beam is coupled in via a glass-fiber and an electromagnetic actuator. The signal is derived from the signal response of the detector by Fourier transformation. 

Fiber optic sensors based on polymer swelling offer several potential advantages. They can be designed so that the optical measurement is separated from the polymer by a diaphragm so that the measurement can not be affected by the optical properties of the sample. Unlike fiber optic sensors based on indicator absorbance or luminescence, photodegradation is not a potential source of sensor instability. Measurements can be made in the near infrared region of the spectrum and take advantage of inexpensive components available for fiber optic communications. 

Raman spectroscopy failed to live up to its original expectation when the technique was discovered. This was due to instrumental problems, high cost of the instrument, and the fluorescence problem. However, with improvement in instrumentation, the use of a near infrared laser with FT-Raman, the introduction of fiber optics, the number of applications (some of which were discussed in Chapter 3) has escalated. The applications are expanded in this chapter, which deals with materials applications involving structural chemistry, solid state, and surfaces. Additional applications are presented in Chapter 5 (analytical applications), Chapter 6 (biochemical and medical applications) and Chapter 7 (industrial applications). 

---