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