Fiber Optics 12812
Fiber Optics 12812

Fiber Optics 12812

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  • Pages: 9 (4488 words)
  • Published: November 23, 2018
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Fiber optics produced by special methods from silica glass and quartz which

replaced copper wire is very useful in telecommunications, long distance

telephone lines and in examining internal parts of the body (endoscopy).

Equipment for photography is available with all current fiber-optic endoscopes.

Through a process known as total internal reflection, light rays beamed into the

fiber can propagate within the core for great distances with remarkably little

attenuation or reduction in intensity. In general, the methods of fiber

production fall into three categories; (a) the extrusion method for synthetic

fibers; (b) hot drawing of fibers from molten bulk material through an orifice;

and (c) drawing of uncoated, coated and multiple fibers from assemblies of rods

and tubes fed through a hollow cylindrical furnace. Three forms of fiber optics

components have been proposed for the improvement of the image quality, field

angle and photographic speed of various types of optical systems. These fiber

optics elements, in the form of a field flattener, a conical condenser and

distortion corrector, can be used separately or combined into a single unit

called a “Focon”. BOGAZICI UNIVERSITESI MAKINA

MUHENDISLIGI DEPARTMANI MALZEME DERSI DONEM PROJESI

YAZ OKULU 2000 OZET Gunumuzde bak?r tellerin yerini alan silikon cam?ndan

ve kristalinden uretilen fiber optikler, telekomunikasyonda, uzun mesafeli

telefon hatlar?nda ve insan vucudunun ic k?s?mlar?n?

inceleyen endoskopilerde kullan?lmaktad?r. Fotograf ekipmanlar?nda

da butun fiber-optik endoskoplara kullan?lmaktad?r. Tam ic yans?ma

olarak bilinen islem yoluyla, fiberin icinde toplanan ?s?k

?s?nlar?, uzun mesafeler boyunca siddetinde kucuk

bir azalma ve bozulmayla yol alabilmektedir. Genellikle, fiber uretimleri uc

kategoridedir; Sentetik fiber uretiminde d?s?na c?karma

methodu; Erimis dokme maddelerden ag?zlar?na dogru olusan

fiberlerin s?cak cizimleriyle, kaplanm?s,kaplanmam?s

veya kar?s?k fiberlerin cizimleriyle. Uc cesit olan

...

fiber optik parcalar?; goruntu kalitesini, cesitli optik

sistemlerdeki alan ac?s? ve fotografik h?zlar? gelistirmek

icin dusunulmustur. Bu fiber optik elemanlar?; alan duzlestirici,

konik yogunlast?r?c? ve sapma duzenleyici sekillerindedir

ve ayr? veya “Focon” ad? verilen unite icin birlesmis

olarak kullan?labilirler. LIST OF FIGURES Figure 2.1 Photograph of the

earliest bundle of uncoated aligned fibers Page 7 Figure 3.1 Core of a step

index fiber Page 8 Figure 3.2 Schematic diagram of a typical fiber drawing Page

9 Figure 3.3 Preform manufacturing apparatus used in Silica-Quartz Page 11

Figure 3.4 Comparison of static,dynamic and spitial filtering imagery Page 12

Figure 4.1 Field flattener system of photography Page 13 Figure 4.2 Showing the

image transmission through a conical fiber bundle Page 14 Figure 4.3 Fiber

optics distortion correctors Page 14 Figure 4.4 Limiting resolution of Focon

system Page 15 Figure 5.1 Single lens reflex camera Page 16 TABLE OF CONTENTS 1.

INTRODUCTION 2. HISTORY OF FIBER OPTICS 3. WHAT IS FIBER OPTICS? 3.1 WHAT IS

SILICA? 3.2 WHAT IS QUARTZ? 3.3 WHAT IS ENDOSCOPIC PHOTOGRAPHY? 4. ENDOSCOPIC

PHOTOGRAPHY ELEMENTS 4.1 FIELD FLATTENER 4.2 CONICAL CONDENSER 4.3 DISTORTION

CORRECTOR 4.4 FOCON RESOLUTION 5. ENDOSCOPIC PHOTOGRAPHY TECHNIQUES 5.1 COLOUR

PHOTOGRAPHY WITH FIBRE-OPTIC ENDOSCOPES 5.2 CINE- ENDOSCOPY 5.3 CLOSED CIRCUIT

COLOUR TELEVISION ENDOSCOPY 5.4 GASTRO-CAMERA EXAMINATION 6. CONCLUSION 7.

REFERENCES 8. APPENDIX 1. INTRODUCTION The technology of fiber drawing for

nonoptical applications is old and fairly standard. Very-small-diameter glass

and quartz fibers were made as early as by Faraday. In the early stages of the

production of glass fibers on an industrial scale, the main application of the

fibers was envisaged in the textile industry. More recently, they have been used

for insulation against sound, heat and electricity. Presently, very fine fibers

are being made of materials such as glass, quartz, nylon, polystyrene,

polymethylcrylate. O

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these, glasses, quartz and plastics are preferred for

optical use because of their higher visible light transmission, longer thermal

working range, better surface characteristics and mechanical strength.

Furthermore, it has been shown that glass fibers can have greater tensile

strength than can be expected from the bulk material. 2. HISTORY OF FIBER OPTICS

The conduction of light along transparent cylinders by multiple total internal

reflections is a fairly old and well known phenomenon. It is entirely possible

that grecian and other ancient glassblowers observed and used this phenomenon in

fabricating their decorative glassware. In fact, the basic techniques used by

the old Venetian glassblowers for making ‘millifiore’ form an important

aspect of present-day fiber optics technology. However, the earliest recorded

scientific demonstration of this phenomenon was given by John Tyndall in 1870.

In demostration Thyndall used an illuminated vessel of water and showed that,

when a stream of water was allowed to flow through a hole in the side of the

vessel, light was conducted along the curved path of the stream. In 1951 when

A.C.S. van Heel in Holland and H.H. Hopkins and N.S. Kapany studied on the

transmission of images along an aligned bundle of flexible glass fibers. But it

was the year 1956 that Kapany first applied the term ‘fiber optics’ to this

field and described its principle and various of possible applications. Kapany

defines fiber optics as the art of the guidance of light, in the ultraviolet,

visible and infrared regions of the spectrum, along transparent fibers through

predetermined paths. Between 1957 and 1960 Potter, Reynolds, Reiffel and Kapany

investigated the use of scintillating fibers for tracking high energy particles.

Potter also investigated the theory of skew ray propagation along fibers in some

detail. One of the biggest application area of fiber optics is in medicine.

Hirschowitz have been working on the developement of fiber optics gastroduodenal

endoscopes and Kapany have been researching fiber optics in gastrocopy,

bronchoscopy, retroscopy and cyctoscopy. Kapany, Drougard and Ohzu have made

basic studies on image transfer characteristics of fiber assemblies. 3. WHAT IS

OPTICAL FIBRES? Optical fibres are glass or plastic waveguides for transmitting

visible or infrared signals. Since plastic fibres have high attenuation and are

used only in limited applications, they will not be considered here. Glass

fibres are frequently thinner than human hair and are generally used with LEDs

or semiconductor lasers that emit in the infrared region. For wavelengths near

0.8 to 0.9 m, gallium arsenide-aluminum gallium arsenide (GaAs-AlxGa1 – xAs)

sources are used, and, for those of 1.3 and 1.55 m, indium phosphide-gallium

indium arsenide phosphide (InP-GaxIn1 – xAsyP1 – y) sources are employed. As

noted earlier, optical fibres consist of a glass core region that is surrounded

by glass cladding. The core region has a larger refractive index than the

cladding, so that the light is confined to that region as it propagates along

the fibre. Fibre core diameters ranges between 1 and 100 m, while cladding

diameters are between 100 and 300 m. Fibres with a larger core diameter are

called multimode fibres, because more than one electromagnetic-field

configuration can propagate through such a fibre. A single-mode fibre has a

small core diameter, and the difference in refractive index between the core and

cladding is smaller than for the multimode fibre. Only one electromagnetic-field

configuration propagates through a single-mode fibre. Such fibres have the

lowest losses and are the most widely

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