Graded-index fiber − The core refractive index is made to vary as a function of the radial distance from the center of the fiber. Optical fibres are of small size and have lightweight as compared to electrical cables. The figure The optical fibers have many applications. Multi-mode fiber − These are excited with LED. The digital communication techniques discussed so far have led to the advancement in the study of both Optical and Satellite communications. incident ray is completely reflected back in the water (or medium with higher which light signals can be transmitted from one place to another with a Although optical fiber appears to be only a simple thread, it is actually composed of two structures similar to water and air. The power loss is very low and hence helpful in long-distance transmissions. Let XY be the boundary separating the optically denser An optical fiber can be understood as a dielectric waveguide, which operates at optical frequencies. Principle of Optical Fiber An optical fibre is a thin thread of lengthy, thin material, which is usually in the shape of a cylinder. The core has a diameter of 10 μm to 100 μm. medium (Water or medium with lower refractive index). The amount of network bandwidth a fiber cable can carry easily exceeds that of a copper cable with similar thickness. At this interface also, the angle of incidence is greater than the critical angle, so it again suffers total internal reflection. (ii) What are the necessary conditions for this phenomenon to occur? In this way light can be taken anywhere because fibers have enough flexibility. Though fiber optic cables last longer, the installation cost is high. Optical fiber is the technology associated with data transmission using light pulses travelling along with a long fiber which is usually made of plastic or glass. The optical frequency of 2 x 10. Hence, such a point is called as Critical angle $\phi _c$. Optical fibers are also unaffected by electromagnetic interference. In practical fibers, the cladding is usually coated with a tough resin coating and an additional buffer layer, which may be further surrounded by a jacket layer, usually plastic. Optical fiber can also be called an optical waveguide, since it is a … These are not affected by electrical noise. Reflection theory c. Light theory d. Snell’s law View Answer: Answer: Option D Solution: 124. A fiber made of a core and cladding with two reflective indices near and clad is called step index. The following figure explains the parts of an optical fiber. Acceptance Angle or Half Angle of Acceptance Cone: The maximum angle with the axis of the optical fibre at which the light entering propagates through the fibre by suffering repeated total internal reflections at the core-cladding interfaces is called the acceptance angle or half-angle of acceptance cone. The basic components are light signal transmitter, the optical fiber, and the photo detecting receiver. The refractive index is high in core and lower in cladding. Cladding has a refractive index n2 which is less than n1. The number of repeaters are to be increased with distance. This phenomenon is known as total internal reflection. Resulting image illustrates a bunch of fiber optic cables. Optical fibers are fine transparent glass or plastic fibers which can propagate light. that the light travels in the core in a guided manner. It is composed of a single-mode pigtail fiber as well as a collimating... 86-760-88338926 interface and θr = angle of reflection at the air-core interface. (numerical value) of merit which describes the light collecting ability of Optical fiber uses the nature of refractive index. Previous Topic: Communication Channels: Wires, Cables, Optic Fibres. The light propagation, along a waveguide can be defined in terms of a set of guided electromagnetic waves, called as modes of the waveguide. The following is a brief introduction to the insertion and return loss of the connector based on the working principle of the optical fiber connector: The optical fiber … The amount of data transmission is higher in fiber optic cables. A bunch of such optical fibres forms optical fibre cable. The optical fibre is a device which works on the principle of total internal reflection by which light signals can be transmitted from one place to another with a negligible loss of energy. Presented by – Ram Singh Patel Roll no.-CSJMA13001390104 ECE (4rd year),UIET, Kanpur Submitted to:- Er. along XY. The core and the cladding are enclosed in an outer protective jacket made of plastic to provide strength to the optical fibre. Silicon tetrachloride vapours are burnt in the same flame so that an oxidized … Optical fibres provide a high degree of signal security as it is confined to the inside of fibre and cannot be tapped and tempered easily. 4. (2) Electrical signals are converted into light signals. axis of the fibre. If the angle The raw material for the manufacture of fiber optic cables is glass, which is cheaper than copper. Fibre optic fibres do not carry high voltages or current. are measured w.r.t. They are flexible and very high tensile strength. The angle made by th… consider a ray of light PQ incident at the air-core interface at angle θi Therefore, the ray suffers total internal reflection at the core-cladding interface and strikes the opposite interface. optical fibre is called its numerical aperture. The light detector receives the optical pulses and converts them into electrical pulses 5. If communication is over the air the systems are usually known as free space communications; if optical fiber is used, then these systems are named Optical Fiber Communications (OFC) and use infrared wavelengths. through the optical fibre is sometimes referred as an optical waveguide. This cylinder is known as the Core of the fiber. The electromagnetic energy travels through it in the form of light. All the angles The basic working principle of optical fiber sensor is to light from the light source signal through optical fiber to the modulator, the parameters and enter the modulation OuDeGuang interaction under test, leading to the optical properties of the light (such as light intensity, wavelength, frequency, phase, polarization, etc.) The electromagnetic energy travels through it in the form of light. The difference between the two indices is very small of order 10-3. Following image depicts a bunch of fiber optic cables. The face SR is perpendicular to the This image shows the structure and working principle of the optical Fibre. Metal wires are preferred for transmission in optical fiber communication as signals travel with fewer damages. Fiber optic cables last longer than copper cables. In step index the density of the core remains constant from center of edges and the refractive index changes in a step fashion from center of fiber (core) to outer shell (cladding. Principle of operation 3. Protects the core from absorbing unwanted surface contaminants. It is a The fibre optic sensor has an optical fibre connected to a light source to allow for detection in tight spaces or where a small profile is beneficial. The communication system of fiber optics is well understood by studying the parts and sections of it. Depending upon the material composition of the core, there are two types of fibers used commonly. The optical frequency of 2 x 10 14 Hz can be used and hence the system has higher bandwidth. The most commonly used optical fiber is single solid di-electric cylinder of radius a and index of refraction n1. This fibre is then covered with a protective plastic sheath to obtain a fine optical fibre. The following figure shows these terms clearly. Step-index fiber − The refractive index of the core is uniform throughout and undergoes an abrupt change (or step) at the cladding boundary. indices of core and cladding is very small. The core is enclosed by a cover of glass or plastic called cladding. Single- and multi-mode fibres 4. 1: A glass rod having a definite An optical fibre is a thin, transparent fibre, usually made of glass or plastic, for transmitting light. If the angle of incidence $\phi _1$ is much larger, then the refracted angle $\phi _2$ at a point becomes Π/2 . The physical advantages of fiber optic cables are −. refractive index is constantly heated by rotating it on the flame of a burner. Fiber optics support a higher capacity. Most When light travels from a medium of a lower refractive index to that of a higher refractive index, it bends towards the normal. The weight of these FOC cables is much lighter than the copper ones. Step – 2: The performed glass rod is then heated in a fibre drawing furnace. The device or a tube, if bent or if terminated to radiate energy, is called a waveguide, in general. Applying Snell’s law at the air-core interface. When Somesh Malhotra Er. It consists of a very thin fibre of silica or glass or plastic of a high refractive index called the core. The light propagation, along a waveguide can be described in terms of a set of guided electromagnetic waves, called as modesof the waveguide. Although fiber optics offer many advantages, they have the following drawbacks −. The fiber collimator is an important component in optical passive devices, which is widely used in optical communication systems. If light is incident on a cable end with an angle of incidence greater than the critical angle then the light will remain trapped inside the glass strand. At the other end, the ray suffers refraction and emerges out of the optical fibre. ray moves along the surface of water i.e. In optical fibre system transmission losses are as low as 0.1 db/km. Hence, more protection is needed than copper ones. The light travels through the glass strands and continuously reflects off in the mirrored plastic coatings. Light losses in fibres Fibre is a transparent cylinder made of a dielectric. 1. Further refraction is not possible beyond this point. such that ∅ is greater than the critical angle θc. ic, there will be no refracted ray. When a ray of light is incident on the core of the optical fibre at a small angle, it suffers refraction and strikes the core-cladding interface, As the diameter of the fibre is very small hence the angle of incidence is greater than the critical angle. Hence the communication Lecture 3: Fibre Optics Lecture aims to explain: 1. Let ∅ be the angle of incidence at the core-cladding interface Fibre applications in telecommunications 2. Fabrication The end of the rod is pulled at a constant rate to form a thin fibre containing the core and the cladding. For an optically dense material, if the reflection takes place within the same material, then such a phenomenon is called as internal reflection. The working principle of optical fiberis the transmission of the information in the form of light atoms otherwise photons. The additional elements such as fiber and cable splicers and connectors, regenerators, beam splitters, and optical amplifiers are employed to improve the performance of the communication system. fibre is a device which works on the principle of total internal reflection by An optical fiber is a cylindrical dielectric waveguide that transmits light along its axis, by the process of total internal reflection. higher refractive index). light takes place. glass rod. The critical optical fibre. The optical change, become a modulated signal source, after a fiber into light detector, … Fiber optic cables are immune to electromagnetic interference. It is a solid fibre whose outer surface is treated such that there is the formation of core and cladding with different refractive indices. Principle and major types The optical fibre consists of the core and the cladding, which have different refractive indexes. The area where light is transmitted is called the core, and the external area is … Used for connecting fire, police, and other emergency services. Where θi = angle of incidence at the air-core An optical fiber can be agreed as a dielectric waveguide, which works at optical frequencies. The largest possible value of NA is unity, Numerical Aperture for Step Index Fibre in Terms A fibre-optic gyroscope (FOG) senses changes in orientation using the Sagnac effect, thus performing the function of a mechanical gyroscope.However its principle of operation is instead based on the interference of light which has passed through a coil of optical fibre, which can be as long as 5 kilometres (3 mi). The optical fiber acts as a wave guide and transmits the optical pulses towards the receiver, by the principle of total internal reflection. By definition, “The ratio of the speed of light in a vacuum to that in matter is the index of refraction n of the material.” It is represented as −, c = the speed of light in free space = 3 × 108 m/s, v = the speed of light in di-electric or non-conducting material, Generally, for a travelling light ray, reflection takes place when n2 < n1 . > μcladding > μair. For understanding the working principle of optical fiber cable clearly, we first further learn the components of an optical fiber cable. Hence, they are safer than electrical cables. The device or a tube, if bent or if terminated to radiate energy, is called a waveguide, in general. . The refractive index of the cladding is less than that of the core (which is a must condition for the working of the optical fibre). Since these cables are di-electric, no spark hazards are present. The normal is a line that is perpendicular to the interface of two mediums. incidence iC, the angle of refraction is 90° and hence the refracted Statement: When a light ray goes from denser to rarer medium at an angle greater than critical angle, the ray is totally reflected in first (denser) medium. Thus it satisfies the need for security which is required in banking and defence. At a particular angle of A light ray, if passed into a glass, at such condition, it is totally reflected back into the glass with no light escaping from the surface of the glass. of Relative core-cladding index difference (D), For an optical fibre, the difference between refractive A fundamental optical parameter one should have an idea about, while studying fiber optics is Refractive index. The bent of light ray at the interface is the result of difference in the speed of light in two materials that have different refractive indices. Fiber cables rated at 10 Gbps, 40 Gbps, and 100 Gbps are stand These cables are formed of two materials with different refractive indices. You can see in this image the two layers of the Optical Fiber, known as Core and cladding. What is optic fibre? Please clarify whether the core is solid or hollow. This reduces cross-talk between the fibers, or reduces flare in fiber bundle imaging applications. The transmission bandwidth of the fiber optic cables is higher than the metal cables. This process is called “Total Internal Reflection”. layer of silicon-di-oxide is uniformly deposited on the outer surface of the When the incident angle $\phi _1$ is greater than the critical angle, the condition for total internal reflection is satisfied. Total Internal Reflection Principle. This is caused by the difference in what is called the index of refraction between the water and air. Whenever light gestures are transmitted through the optical cable, then they do not reflect the cladding & core within a sequence of zigzag bounces, sticking to a method is named as total internal reflection. A solid di-electric material surrounds the core, which is called as Cladding. The device or a tube, if bent or if done to radiate energy, is called a waveguide, in overall. The electromagnetic energy travels through it in the form of light. (i) State the principle on which the working of an optical fiber is based. As the angle of incidence FIBRE OPTICSOptical Fibre is new medium, in which information (voice, Data or Video) is transmitted through a glass or plastic fibre, in the form of light Transmission sequence: (1) Information is encoded into electrical signals. Ppt on optical fiber 1. glass compositions. Your email address will not be published. r = 90o, When i > The Principles Behind Fiber Optics, Fabrication Of Optical Fibers, Fiber Classifications, Other Applications Optical fiber is a very thin strand of glass or plastic capable of transmitting light from one point to another. A fiber optic cable is a long-distance network telecommunications cable made from strands of glass fibers that uses pulses of light to transfer data. It is represented as −, n1 and n2 are the refractive indices of two materials. The incident angle and refracted angle are shown in the following figure. The major elements of an optical fiber communication system are shown in the following figure. They work under the principle of total internal reflection from diametrically opposite walls. Thus, the ray of light reaches the other end of the fibre after suffering repeated total internal reflections along the length of the fibre. 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