FIBER OPTICS

INTRODUCTION

A fiber - optic cable is a technology that uses glass (or plastic) threads (fibers) to transmit data. It is made up of 100 or more incredibly thin strands of glass or plastic fibers known as Optical Fibers. Each one is less than a tenth as thick as human hair and can carry 10 million telephone calls.

Optical fibers are widely used in fibers-optic communication, which permits transmission over longer distances and at higher data rates than other forms of wired and wireless communications.

How the Fiber Optic works..??There are 2 things which keeps light inside the fiber optics.

The first one is the structure of the cable , which is made up of 2 separate parts.

The main part of cable - in the middle - is called CORE and that’s the bit the light travels through. Wrapped around the outside the core is another layer of glass called CLADDING .

The CLADDINGS’S job is to keep the light signals inside the core. It can do this because it is made of a different type of glass to the core.

Light travels slower in the cladding than in the core. Any light that tries to leak into the cladding tends to bend back inside the core.

The second is:-Light travels down a fiber – optic cable by bouncing repeatedlyoff the walls. Each tiny photon i.e., particle of light bounces down the pipe like bobsleigh down the pipe like an ice run.We may expect a beam of light , travelling in a clear glass pipe, simply to leak out of edges. But if light hits at a really shallow angle (Less than 42 degrees), it reflects back in again – as though the glass were really a mirror.

This phenomenon is called total internal reflection.

TYPES OF FIBER OPTICS

Other fibers carry light signals down them in what are called MODES. That sounds technical but it just means different ways of travelling : a mode is simply the path that a light beam follows down the fiber.

There are generally two modes of fiber optics :-

1. Single – mode Fiber Optic2. Multi – mode Fiber Optic

SINGLE – MODE FIBER OPTIC

The simplest type of optical fiber is called single – mode. It has a very thin core about 5 – 10 microns (millionths of a meter) in diameter. In a single – mode fiber, all signals travel straight down the middle without bouncing off the edges.

Cable TV, Internet, and telephone signals are generally carried by single – mode fibers, wrapped together into a huge bundle. Cables like this can send information over 100 km (600 miles).

MULTI – MODE FIBER OPTIC

Another type of fiber – optic cable is called multi-mode. Each optical fiber in multi- mode cable is about 10 times bigger than one in a single-mode cable. This means light beams can travel through the core by following a variety of different paths(purple, green and blue lines) - in other words, in multiple different modes. Multi – mode cables can send information only over relatively short distances and are used to link computer networks together.

ADVANTAGES OF FIBER OPTICS Low cost in long run. Low loss of signals, so repeater – less transmission over long distances is possible. Large data carrying capacity. No electro – magnetic radiation ; difficult to eavesdrop. Low weight. Signals contain very little power. No cross – talks between cables.

DISADVANTAGES OF FIBER OPTICS

High investment cost. Need for more expensive optical transmitters and receivers. More difficult and expensive to split than wires.

AREAS OF FIBER OPTICS

Tele – communications Local Area Networks Cable TV CCTV Optical Fiber Sensors

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