Sensor extrinsic optical

Fig. 5.4. Optical Fiber biosensor, (a) Extrinsic optical fiber is used for the guiding the light to and from the sensor area, (b) Intrinsic the receptor molecules are immobilized on the fiber core after decladding of the fiber. The detection is based on fluorescence labels.

Fig. 5.6. (a) Extrinsic optical fiber sensor, where fibers are used to guide input and output signals, (b) Intrinsic optical fiber sensor, where sensor is incorporated into fiber structure... 

Fig. 1.12 Variants of extrinsic optical fiber sensors (Reprinted with permission from Chan et al. (1984). Copyright 1984 IEEE) Table 1.13 Gases commonly detected by optical absorption...

A first broad classification of optical fibres can be carried out according to the sensing location, by distinguishing between intrinsic and extrinsic optical fibre sensors. The extrinsic optical fibre sensors are characterised by the fact that the fibre is simply used as a means to carry light to (and from) an external optical device where the... 

Extrinsic detectors, 22 180 Extrinsic fiber-optic sensors, 11 148 Extrinsic photoconductors, 19 138 Extrinsic semiconductors, 22 236-237 Extrinsic wastes, 10 68 Extruded food packaging, 18 45 Extruded lead-copper alloys, 14 776 Extruded lead-tellurium alloys, 14 778 Extruded rigid foam, 23 404-405 Extruders... 

The fiber optic sensors utilize an extrinsic Fabry-Perot interferometer to spectrally modulate light in proportion to pressure, temperature, or refractive index variations. Because they are based on spectral modulation instead of amplitude modulation, they are not affected by such common problems as fiber bending, connector losses, and aging. 

Optical biosensors based on the use of fiber optics can be classified into two categories intrinsic sensors where interaction with the analyte occurs within an element of the optical fiber, and extrinsic sensors in which the optical fiber is used to couple light, usually to and fi om the region where the light beam is influenced by the measurand. Moreover, biosensors become attractive because they can be easily used by non-specialist personnel and they allow accurate determination with either none or little sample treatment. Therefore, fiber-optic biosensors may be especially useful in... 

Both extrinsic- and intrinsic-type sensors incorporate a transducer element making it an active device. Extrinsic sensors have an external transducer, and the optical fiber just serves the purpose of a light carrier to and from the external transducer whereas, intrinsic sensors have the structure of the optical fiber modified to incorporate the transducer element. In both cases, the transduction mechanisms change the light properties based on interaction with chemical species. 

It was mentioned before that fiber-optic chemical and biosensors are broadly classified into two categories extrinsic- and intrinsic-type sensors. In the extrinsic-type sensors, the fiber is acting as a link connecting optical signals to (and from) the active material (medium) positioned at the end of the fiber, such as the Optode case. In the intrinsic-type sensors, the fiber is modified in different ways, through construction of the sensing component, which will be explained next. 

Recent work has investigated conductive polymers [69,70], sol-gels [71], and chemoresponsive dyes [72] for use as the gas-sensitive transduction medium in fiber optic sensors. In general, fiber optic sensors can be divided into two different sensing architectures extrinsic and intrinsic. If the transduction of the chemical signal into an optical signal occurs within the fiber... 

Due to their high sensitivity to strain, temperature variation, vibration, and acoustic waves, embedded extrinsic Fabry-Perot interferometric optical fiber sensors have been developed to detect delamination, based on changes in the acoustic properties of the materials before and after delamination [41]. Impact events and corrosion cracking generate ultrasonic waves, which can be characterized using elliptical core fiber sensors [40]. The in-line Fabry-Perot interferometer seems well suited for the local detection of shear waves and the characterization of impact-induced damage. 

It is noteworthy that the wetting effect caused PL quenching, as an extrinsic sensing mechanism, is likely extendable to other QD-polymer systems used as chemical vapor sensors for detection of different molecular species. The complexity arises from solid-state optical systems for vapor detections involving a combination of nanoparticles and polymer interaction with chemical species under illumination. This is an important point to which to pay attention in the studying and development of this type of dependable QD-based chemical sensor. 

Direct physical contact between the sensor reagent or transducer and the fiber is not a requirement. The indicator can also be in a sample that is viewed through a window the optical fiber, such as in a flow-injection-analysis sensing scheme used for process control ( ). Although such applications will be an Important part of optical sensor technology, the more demanding approach is the preparation of extrinsic sensors with the reagent phase attached directly to the fiber tip, a requirement for in vivo and in situ applications. The inventive work of sensor chemists now focuses... 

A sensor is a device capable of converting a physical or chemical quantity into readable information. In addition to a topological classification (local or distributed, intrinsic or extrinsic), a more basic classification can be made according to the optical parameter affected by the external factor intensity, phase, wavelength, and polarization. 

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. 

Basically, two fundamental classes of FOS can be distinguished - the intrinsic fiber optic sensor and the extrinsic fiber optic sensor, see Fig. 7.11. An intrinsic FOS takes advantage of measurable changes in the transmission characteristic of the optical fiber itself that means the sensing element is, at one and the same time, the carrier of information from and to the reading unit. Sensor types of this class are predestined for use in smart components because they avoid additional elements. Some extrinsic sensor types (such as micro strain sensors, see Sect. 7.2.2), where the fiber is not used as a sensor... 

Fig. 7.11. Two main classes of fiber optic sensors a intrinsic t5fpe, b extrinsic type. The picture above shows the transmission mode the picture below shows the reflection mode...

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