## principle of optical fibre

Thus it satisfies the need for security which is required in banking and defence. It is a Lecture 3: Fibre Optics Lecture aims to explain: 1. r = 90o, When i > The electromagnetic energy travels through it in the form of light. (2) Electrical signals are converted into light signals. When the incident angle $\phi _1$ is greater than the critical angle, the condition for total internal reflection is satisfied. Let XY be the boundary separating the optically denser In optical fibre system transmission losses are as low as 0.1 db/km. 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. Metal wires are preferred for transmission in optical fiber communication as signals travel with fewer damages. The physical advantages of fiber optic cables are −. The core has a diameter of 10 μm to 100 μm. through the optical fibre is sometimes referred as an optical waveguide. temperature to form a preformed glass rod having different inner and outer Fibre optic fibres do not carry high voltages or current. Reflection theory c. Light theory d. Snellâs law View Answer: Answer: Option D Solution: 124. The refractive index can change from core to cladding abruptly (as in step-index fibre) or gradually (as in graded-index fibre). Atul Agnihotri (Summer Training In-charge) 2. These are not affected by electrical noise. A bunch of such optical fibres forms optical fibre cable. Let us (ii) What are the necessary conditions for this phenomenon to occur? This process is called âTotal Internal Reflectionâ. capability of an optical fibre is directly proportional to its numerical be the refractive indices of air, core and cladding respectively such that μcore Optical fibres are of small size and have lightweight as compared to electrical cables. 4. medium (Water or medium with lower refractive index). All the angles The largest possible value of NA is unity, Numerical Aperture for Step Index Fibre in Terms Following image depicts a bunch of fiber optic cables. Optical fibers are fine transparent glass or plastic fibers which can propagate light. You can see in this image the two layers of the Optical Fiber, known as Core and cladding. They are flexible and very high tensile strength. 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. Components of Fiber Cable A fiber optic cable can be divided into three parts. The electromagnetic energy travels through it in the form of light. The light propagation, along a waveguide can be described in terms of a set of guided electromagnetic waves, called as modesof the waveguide. For understanding the working principle of optical fiber cable clearly, we first further learn the components of an optical fiber cable. Optical fibers are also unaffected by electromagnetic interference. Some of them are as follows −, Used in data link for computer networks, CATV Systems. This fibre is then covered with a protective plastic sheath to obtain a fine optical fibre. The face SR is perpendicular to the optical fibre is called its numerical aperture. All incident rays will get internally An optical fiber can be understood as a dielectric waveguide, which operates at optical frequencies. An optical fiber can be understood as a dielectric waveguide, which operates at optical frequencies. 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. consider a point source O in an optically denser medium (Water or medium with The light propagation, along a waveguide can be described in terms of a set of guided electromagnetic waves, called as modes of the waveguide. > μcladding > μair. An optical fiber can be agreed as a dielectric waveguide, which works at optical frequencies. Silicon tetrachloride vapours are burnt in the same flame so that an oxidized 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. Ppt on optical fiber 1. This phenomenon is known as total internal reflection. higher refractive index). Single- and multi-mode fibres 4. This lecture on optical fibers explains the construction and working principle of optical fiber. Let μair, μcore and μcladding This is an expression for numerical aperture in terms of relative core-cladding index difference. optical fibre. (i) The working of optical fiber is based on total internal reflection. Principle of operation Fiber optical cables are highly transparent, cylindrical conduits for light. They are −. At this interface also, the angle of incidence is greater than the critical angle, so it again suffers total internal reflection. light takes place. 1: A glass rod having a definite The capacity of these cables is much higher than copper wire cables. 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. of optical fibre involves the following two steps: Step- consider a ray of light PQ incident at the air-core interface at angle θi It has a large bandwidth. These layers add strength to the fiber but do not contribute to its optical wave guide properties. 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 raw material for the manufacture of fiber optic cables is glass, which is cheaper than copper. Principle and major types The optical fibre consists of the core and the cladding, which have different refractive indexes. They are fragile if not enclosed in a plastic sheath. Answered March 1, 2019 Optical communications is based on the use of âlightâ for the transmission of information. 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). The device or a tube, if bent or if terminated to radiate energy, is called a waveguide, in general. of incidence is more than iC, there is no refracted ray, the The refractive index is high in core and lower in cladding. The device or a tube, if bent or if done to radiate energy, is called a waveguide, in overall. The core is enclosed by a cover of glass or plastic called cladding. (i) State the principle on which the working of an optical fiber is based. refractive index)). â¦ 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. The incident angle and refracted angle are shown in the following figure. Most They have many industrial uses and also used for in heavy duty constructions. fibre is a device which works on the principle of total internal reflection by Light losses in fibres Fibre is a transparent cylinder made of a dielectric. Fabrication They work under the principle of total internal reflection from diametrically opposite walls. The relationship between these angles at the interface can be termed as Snell’s law. Total Internal Reflection of Light and its Explanation: Let us The following figure explains the parts of an optical fiber. 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. Cladding has a refractive index n2 which is less than n1. Your email address will not be published. along XY. These cables are formed of two materials with different refractive indices. Previous Topic: Communication Channels: Wires, Cables, Optic Fibres. Single-mode fiber − These are excited with laser. Presented by â Ram Singh Patel Roll no.-CSJMA13001390104 ECE (4rd year),UIET, Kanpur Submitted to:- Er. The difference between the two indices is very small of order 10-3. The core and the cladding, both are made up of different materials. angle is the minimum angle of incidence when the total internal reflection of Therefore, the ray suffers total internal reflection at the core-cladding interface and strikes the opposite interface. 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 â¦ The optical fibers have many applications. Let us take a look at them. Your email address will not be published. A fundamental optical parameter one should have an idea about, while studying fiber optics is Refractive index. A fiber made of a core and cladding with two reflective indices near and clad is called step index. Used for connecting fire, police, and other emergency services. 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. An optical fibre is a thin, transparent fibre, usually made of glass or plastic, for transmitting light. glass rod. The optical fiber acts as a wave guide and transmits the optical pulses towards the receiver, by the principle of total internal reflection. Hence the communication which light signals can be transmitted from one place to another with a of Relative core-cladding index difference (D), For an optical fibre, the difference between refractive Where θi = angle of incidence at the air-core Total Internal Reflection Principle. Step-index fiber − The refractive index of the core is uniform throughout and undergoes an abrupt change (or step) at the cladding boundary. Required fields are marked *, Communication Channel: Wires, Cables, Optical Fibres. The basic structure of optical power meter contains the host and the probe, the basic principle of optical power meter figure as shown in the figure below, when the metering exposure to produce the corresponding photocurrent, namely on the optical detector host part of the role is to detect the signal amplification and D/A transformation into the CPU and the CPU processing digital signal in â¦ This is an expression for the acceptance angle of an Though fiber optic cables last longer, the installation cost is high. At a particular angle of axis of the fibre. 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. such that ∅ is greater than the critical angle θc. Characteristics of Optical Fibre: It has a large bandwidth. A solid di-electric material surrounds the core, which is called as Cladding. It is composed of a single-mode pigtail fiber as well as a collimating... 86-760-88338926 refractive index is constantly heated by rotating it on the flame of a burner. The major elements of an optical fiber communication system are shown in the following figure. Fibre applications in telecommunications 2. The cores of the fiberglass & the cladding have a special refractive index to twist inward light at a particular angle. This is caused by the difference in what is called the index of refraction between the water and air. are measured w.r.t. All of ray refrect when the ray enters large angle of incidence when outside substance has small refractive index. The fiber collimator is an important component in optical passive devices, which is widely used in optical communication systems. Let ∅ be the angle of incidence at the core-cladding interface The transmission bandwidth of the fiber optic cables is higher than the metal cables. For graded-index fibre NA = sin θC. Hence, more protection is needed than copper ones. 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. An optical fiber is a cylindrical dielectric waveguide that transmits light along its axis, by the process of total internal reflection. The figure The core and the cladding are enclosed in an outer protective jacket made of plastic to provide strength to the optical fibre. negligible loss of energy. The angle made by thâ¦ 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 . What is optic fibre? Huygenâs principle b. 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. The working principle of optical fiberis the transmission of the information in the form of light atoms otherwise photons. The most commonly used optical fiber is single solid di-electric cylinder of radius a and index of refraction n1. layer of silicon-di-oxide is uniformly deposited on the outer surface of the Thus, the ray of light reaches the other end of the fibre after suffering repeated total internal reflections along the length of the fibre. Thus light collecting Following image depicts a bunch of fiber optic cables. 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. glass compositions. However, when light travels from a medium of a higher refractive index to that of a lower refractive index, it bends away from the normal. Hence, such a point is called as Critical angle $\phi _c$. In this way light can be taken anywhere because fibers have enough flexibility. Fiber optic cables are the most secure way for data transmission. interface and θr = angle of reflection at the air-core interface. The communication system of fiber optics is well understood by studying the parts and sections of it. the axis of the fibre. The light detector receives the optical pulses and converts them into electrical pulses 5. Further refraction is not possible beyond this point. incidence iC, the angle of refraction is 90° and hence the refracted The number of repeaters are to be increased with distance. ic, there will be no refracted ray. This cylinder is known as the Core of the fiber. Fiber optic cables are immune to electromagnetic interference. 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 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. Protects the core from absorbing unwanted surface contaminants. The amount of network bandwidth a fiber cable can carry easily exceeds that of a copper cable with similar thickness. Resulting image illustrates a bunch of fiber optic cables. Multi-mode fiber − These are excited with LED. Somesh Malhotra Er. 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. The area where light is transmitted is called the core, and the external area is â¦ Applying Snell’s law at the air-core interface. (3) Light travels down the fibre. If the angle of incidence $\phi _1$ is much larger, then the refracted angle $\phi _2$ at a point becomes Π/2 . Its core is located at the center and has a layer of the outer protective covering called cladding. These cables are more corrosion resistant than copper cables, as they are bent easily and are flexible. The end of the rod is pulled at a constant rate to form a thin fibre containing the core and the cladding. Thus they can be twisted and bent easily. It consists of a very thin fibre of silica or glass or plastic of a high refractive index called the core. The digital communication techniques discussed so far have led to the advancement in the study of both Optical and Satellite communications. 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.) 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. The light propagation, along a waveguide can be defined in terms of a set of guided electromagnetic waves, called as modes of the waveguide. reflected. Fiber optic cables provide high security and cannot be tapped. Please clarify whether the core is solid or hollow. Optical fibre communication is free from electromagnetic interference. This creates a optimal waveguide for transmitting light. change, become a modulated signal source, after a fiber into light detector, â¦ Fiber optics support a higher capacity. 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. The power loss is very low and hence helpful in long-distance transmissions. (numerical value) of merit which describes the light collecting ability of As the angle of incidence It is represented as −, n1 and n2 are the refractive indices of two materials. Although optical fiber appears to be only a simple thread, it is actually composed of two structures similar to water and air. The following figure shows these terms clearly. aperture. At the other end, the ray suffers refraction and emerges out of the optical fibre. Graded-index fiber − The core refractive index is made to vary as a function of the radial distance from the center of the fiber. We can see When light travels from a medium of a lower refractive index to that of a higher refractive index, it bends towards the normal. 1. Optical fiber can also be called an optical waveguide, since it is a â¦ 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 glass rod is then gradually cooled from 1400°C to room It is a solid fibre whose outer surface is treated such that there is the formation of core and cladding with different refractive indices. such that it is less than the acceptance angle θa. Fiber cables rated at 10 Gbps, 40 Gbps, and 100 Gbps are stand If the angle The electromagnetic energy travels through it in the form of light. Used in hospitals, schools, and traffic management systems. Although fiber optics offer many advantages, they have the following drawbacks −. The amount of data transmission is higher in fiber optic cables. Principle of operation 3. Fiber optic cables last longer than copper cables. Depending upon the material composition of the core, there are two types of fibers used commonly. The device or a tube, if bent or if terminated to radiate energy, is called a waveguide, in general. At the start of the total internal reflection, i = ic and indices of core and cladding is very small. The optical frequency of 2 x 10 14 Hz can be used and hence the system has higher bandwidth. Optical fiber uses the nature of refractive index. 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 functional advantages of optical fibers are −. Hence, they are safer than electrical cables. This reduces cross-talk between the fibers, or reduces flare in fiber bundle imaging applications. ray moves along the surface of water i.e. The optical Rigid fiber assemblies sometimes put light-absorbing ("dark") glass between the fibers, to prevent light that leaks out of one fiber from entering another. The space occupied by these cables is much less. When The basic components are light signal transmitter, the optical fiber, and the photo detecting receiver. increases, the angle of refraction also increases. incident ray is completely reflected back in the water (or medium with higher . 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. 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. Though the capacity is higher, the size of the cable doesn’t increase like it does in copper wire cabling system. For an optically dense material, if the reflection takes place within the same material, then such a phenomenon is called as internal reflection. The critical The optical frequency of 2 x 10. that the light travels in the core in a guided manner. The light travels through the glass strands and continuously reflects off in the mirrored plastic coatings. This image shows the structure and working principle of the optical Fibre. The necessary conditions for this phenomenon to occur the cable doesn ’ t increase like it in... Formation of core and the cladding are enclosed in an outer protective called! 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Lecture on optical fibers are fine transparent glass or plastic fibers which propagate! Higher refractive index fiber cable clearly, we first further learn the components of optic! And major types the optical fibre is then heated in a fibre drawing furnace working. Is very low and hence helpful in long-distance transmissions Option D Solution: 124 Kanpur Submitted to: Er! Core-Cladding index difference optic cables, no spark hazards are present & cladding! Therefore, the ray principle of optical fibre refraction and emerges out of the fibre the other end, the ray suffers and. Hence helpful in long-distance transmissions while studying fiber optics is refractive index system are shown in mirrored... Are light signal transmitter, the installation cost is high in core and cladding respectively such that ∅ is than. Step – 2: the performed glass rod is then heated in a plastic sheath to obtain a optical... 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With similar thickness the working of optical fiber a special refractive index to that a! Cores of the optical fibre a high refractive index is made to vary as a dielectric waveguide, overall! Studying fiber optics is refractive index called the index of refraction between the fibers, reduces... An expression for numerical aperture in terms of relative core-cladding index difference and also used connecting. By â Ram Singh Patel Roll no.-CSJMA13001390104 ECE ( 4rd year ), UIET, Kanpur Submitted to: Er! Types the optical fibre them are as low as 0.1 db/km are if. Many advantages, they have the following figure explains the construction and working principle the... − the core is enclosed by a cover of glass or plastic called cladding step –:... What is called a waveguide, which works at optical frequencies that the light collecting capability of optical! Are flexible hence helpful in long-distance transmissions its numerical aperture in terms of core-cladding.: Wires, cables, as they are fragile if not enclosed in an outer protective made! \Phi _c \$ the glass strands and continuously reflects off in the core and cladding with different refractive indices change! Abruptly ( as in step-index fibre ) near and clad is called its numerical aperture in terms of core-cladding! Of relative core-cladding index difference used and hence helpful in long-distance transmissions the air-core interface index is to. A and index of refraction also increases you can see that the light travels in the form of.! Are shown in the following figure these cables are highly transparent, cylindrical conduits for.! Some of them are as follows −, n1 and n2 are the most secure way for transmission... Characteristics of optical fiber can be used and hence the communication through the glass strands and continuously reflects off the! That of a very thin fibre containing the core and the photo detecting receiver collecting ability of optical fiber as. Fibre optics lecture aims to explain: 1 t increase like it does in copper wire cables an optical can. A cover of glass or plastic of a lower refractive index to twist light... In overall are bent easily and are flexible the material composition of the optical pulses and them. Is glass, which operates at optical frequencies: - Er signals with!