Fiber optics

Fiber optics is a transmission line or a similar cable is made of glass or plastic is very smooth and smaller than a strand of hair, and can be used to transmit light signals from one place to another by using the principle of total internal reflection phenomenon. The light source used is usually a laser or LED. This cable diameter of about 120 micrometers. Fiber optic cables are generally composed of two main parts, namely: core (nucleus) and cladding. Core optical fiber serves as a medium of light propagation, through the phenomenon of total internal reflection. Cladding is the outer layer that wraps the core and reflect the light that radiates out back into the core. In addition to the two main layers are also jacket / buffer coating, which is a layer of protective material that protects the core and cladding of the environment.
-> In order to spread the light perfectly reflecting the requirement that the core must have a refractive index of refraction larger than the cladding, so that when the light enters the nucleus with the angle of incidence greater than the critical angle will undergo total internal reflection repeated in the core .
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Division of optical fibers can be seen from the two kinds of differences:
1. Based on the mode of propagation (spread) are propagated:
a. Single mode: optical fiber core is very small (typically about 8.3 microns), very narrow core diameter approaches the wavelength of light that goes into it is not bouncing into the wall sleeve (cladding). Courant core single-mode optical fiber is made of silica glass (SiO2) with a small amount of glass Germania (GeO2) to increase the refractive index. To obtain good performance on these cables, usually for the slug size is about 15 times the size of the core (about 125 microns). Cables for the most expensive of this type, but has a weaker (less than 0.35dB per kilometer), thus enabling very high speed from a great distance. The latest standard for this cable is the ITU-T G.652D, and G.657. The light source used in the form of laser and distance of single-mode> 60 km
b. Multi mode: optical fiber with a core diameter of a rather large which makes laser in it will be bouncing on the wall cladding which can reduce the bandwidth of the optical fiber type. LED light source and the distance is about 300 500 m
2. Based on the distribution of the refractive index of the core:
a. Step index: in step index optical fibers, the core has a homogeneous refractive index. Inddeks core bias greater than the cladding to form a ladder at the core-cladding boundary.
b. Graded index: core refractive index approached closer to the smaller cladding. So in graded index, central core has a refractive index value the most. Graded index fiber makes it possible to bring greater bandwidth, due to the widening pulses that occur can be minimized.

          

            In the propagation of light in optical fibers, light can not all power dijalarkan perfectly. There is a small power loss due to external factors such as fiber curvature (bending losses). Bending loss is one of the few sources of loss optical fiber. Bending loss is caused by the bending of the optical fiber exceeds a certain diameter. Where there is a change in the angle of incidence so that the fiber optic loss of some modes of propagation, as a result of light out of the fiber optic core. These circumstances in optical fiber communication is very detrimental. But from the other side can be used as a displacement sensor and can be used as an extensometer.
Fiber optics can be applied as a sensor for the measurement of various parameters such as friction, temperature, pressure, humidity, fluid flow rate, rotation rate, the concentration of a substance, Iistrik field, magnetic field, and chemical analysis. "Excellence optic fiber as a sensor include no direct contact with the object of measurement, not using electricity as a signal, high measurement accuracy, relatively insensitive terbadap electric and magnetic induction, can be monitored remotely, can be connected to the system via the data communication interface (inteiface) and small dimensions and lightly. working principle of optical fiber as a sensor based on intensity modulation, modulation and phase modulation wavelength of light as a cue.

  -> Other than a sensor utilizing physics, can also be used as biosensors. NRL research has developed a fiber-optic biosensor which uses antibody, lectin, and antibiotics on the surface of an optical fiber to achieve selectivity. The system is very well adapted to detect environmental pollutants and hazardous chemicals or biological materials
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Fiber optic biosensor is a device that measures the fluorescent complex formation on the surface of an optical fiber. Antibodies, lectins, and antibiotics provides a mechanism to recognize an analyte of interest and immobilizing a fluorescent complex on the fiber surface. Biosensor is a rapid, sensitive, and permits analysis of hazardous materials away from existing instruments. A portable sensor has been manufactured and tested in the detection of explosives in groundwater. Antibody-coated fibers were stable for two years of storage before use. Biosensors have been developed to detect explosives, pollutants, pathogens, and toxic materials.
Bibliography
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_______. Fiber Optic. http://www.lipi.go.id/intra/database2.cgi? cetakprogram &&& 1036006479 & 2011 & 10 36006479 & 1296790120 & 1012548352 && research
_______. Fiber Optic Sensors. http://www.nrl.navy.mil/accomplishments/materials/fiber-optic-sensors/
_______. Fiber Optics. http://1100060884.blog.binusian.org/category/fiber-optik/
_______. Fiber Optics. http://id.wikipedia.org/wiki/Serat_optik
Pramod, YP and Rohedi, A Y.2008.Aplikasi Directional Coupler Optical Fiber as Sensor Shift. Journal of Physics and Applications, Vol 4 # 2

Fiber optics 2013-02-25T09:33:00+07:00 Rating: 4.5 Diposkan Oleh: Rumah Minimalis