• Optical fibers are long, thin strands of very pure glass usually the diameter of a human hair; 120 µm.• They are arranged in bundles called optical cables and used to transmit light signals over long distances. (up to 50 km.)
• Core – thin glass center of the fiber .• Cladding – outer optical material made from glass surrounding the core.• Buffer Coating – plastic coating that protects the fiber . 1.Core• Jacket – The bundles are 2.Cladding protected by the cables’ outside covering called jacket. 3.Buffer 4.Jacket
• Let a ray of light be incident on the fibre making the critical angle with the axis as shown. • The light ray passes passes into the fibre. • This ray forms the incident angle. • If the incident theta is greater than the critical angle then the ray suffers total internal reflection. • So all the energy in the ray of light is reflected in the core and none escapes into the cladding. • The reflection get repeated throughout the fibre leading to a total internal reflection. Ɵ 2Ɵ1
Types of Optical Fibers.Optical fibers come in two types: Single-mode fibers Multi-mode fibers• Single-mode fibers are used to transmit one signal per fiber (used in telephone and cable TV). They have small core (9 microns in diameter) and transmit infra-red light from laser. • Multi-mode fibers are used to transmit many signals per fiber (used in computer networks). They have larger cores (62.5 microns in diameter) and transmit infra-red light from LED.
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ADVANTAGES OF OPTICAL FIBERS1. It has a very high information carrying capacity.2. It has less attenuation.3. The cost of production is less compared to copper. Less Signal Degradation occurs throughout the fibre.4. Greater safety and immunity to EMI or RFI, moisture and corrosion.5. It’s flexible and easy to install in tight conduits.6. It’s dielectric in nature so can be laid in electrically sensitive surroundings.7. You wont come across any situations of cross talking or any disturbances.8. Power usage is less compared to many other cables.
Disadvantages• Fiber optics are that the cables areexpensive to install.• The termination of a fiber opticcable is complex and requires specialtools.• They are more fragile than coaxial cable.
It’s the backbone of many long distancecommunications. It’s widely used in computerdata communications and networks. (LAN, WANetc..)It’s used in many lighting systems.It’s used in video and data transmissions.It’s used in transmitting broadbandsignalsThe cables are ideally suited for high-reliability settings such in commercial andmilitary jet aircraft, satellite and otherspace-based applications.It’s used by Surgeons to view organsinside the body that cannot be vieweddirectly.It’s also used in the biomedical industry.