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 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 optical frequency of 2 x 10 14 Hz can be used and hence the system has higher bandwidth. Although fiber optics offer many advantages, they have the following drawbacks −. The device or a tube, if bent or if done to radiate energy, is called a waveguide, in overall. reflected. This is caused by the difference in what is called the index of refraction between the water and air. > μcladding > μair. optical fibre is called its numerical aperture. This fibre is then covered with a protective plastic sheath to obtain a fine optical fibre. The space occupied by these cables is much less. The raw material for the manufacture of fiber optic cables is glass, which is cheaper than copper. change, become a modulated signal source, after a fiber into light detector, … These are not affected by electrical noise. Huygen’s principle b. Used for connecting fire, police, and other emergency services. Thus light collecting This process is called “Total Internal Reflection”. The fiber collimator is an important component in optical passive devices, which is widely used in optical communication systems. It is represented as −, n1 and n2 are the refractive indices of two materials. If the angle of incidence $\phi _1$ is much larger, then the refracted angle $\phi _2$ at a point becomes Π/2 . such that it is less than the acceptance angle θa. This lecture on optical fibers explains the construction and working principle of optical fiber. These cables are more corrosion resistant than copper cables, as they are bent easily and are flexible. They are flexible and very high tensile strength. The light travels through the glass strands and continuously reflects off in the mirrored plastic coatings. incidence iC, the angle of refraction is 90° and hence the refracted Optical fibers are fine transparent glass or plastic fibers which can propagate light. 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. This reduces cross-talk between the fibers, or reduces flare in fiber bundle imaging applications. refractive index is constantly heated by rotating it on the flame of a burner. The critical Following image depicts a bunch of fiber optic cables. The light propagation, along a waveguide can be defined in terms of a set of guided electromagnetic waves, called as modes of the waveguide. Fiber optic cables are immune to electromagnetic interference. Fiber optic cables are the most secure way for data transmission. 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 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. increases, the angle of refraction also increases. 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). that the light travels in the core in a guided manner. Reflection theory c. Light theory d. Snell’s law View Answer: Answer: Option D Solution: 124. 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. Further refraction is not possible beyond this point. Your email address will not be published. r = 90o, When i > … We can see aperture. The relationship between these angles at the interface can be termed as Snell’s law. Ppt on optical fiber 1. are measured w.r.t. medium (Water or medium with lower refractive index). This is an expression for numerical aperture in terms of relative core-cladding index difference. Fabrication They are fragile if not enclosed in a plastic sheath. The basic components are light signal transmitter, the optical fiber, and the photo detecting receiver. Metal wires are preferred for transmission in optical fiber communication as signals travel with fewer damages. consider a ray of light PQ incident at the air-core interface at angle θi Hence, such a point is called as Critical angle $\phi _c$. Let us take a look at them. The electromagnetic energy travels through it in the form of light. fibre is a device which works on the principle of total internal reflection by Let us glass rod. At this interface also, the angle of incidence is greater than the critical angle, so it again suffers total internal reflection. For an optically dense material, if the reflection takes place within the same material, then such a phenomenon is called as internal reflection. be the refractive indices of air, core and cladding respectively such that μcore For understanding the working principle of optical fiber cable clearly, we first further learn the components of an optical fiber cable. Fiber optic cables provide high security and cannot be tapped. At the start of the total internal reflection, i = ic and Optical fiber uses the nature of refractive index. 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 figure Total Internal Reflection of Light and its Explanation: Let us Single-mode fiber − These are excited with laser. along XY. This image shows the structure and working principle of the optical Fibre. The functional advantages of optical fibers are −. Therefore, the ray suffers total internal reflection at the core-cladding interface and strikes the opposite interface. interface and θr = angle of reflection at the air-core interface. The normal is a line that is perpendicular to the interface of two mediums. Optical fibres are of small size and have lightweight as compared to electrical cables. light takes place. Thus it satisfies the need for security which is required in banking and defence. The difference between the two indices is very small of order 10-3. which light signals can be transmitted from one place to another with a Answered March 1, 2019 Optical communications is based on the use of “light” for the transmission of information. Fiber optic cables last longer than copper cables. optical fibre. They have many industrial uses and also used for in heavy duty constructions. indices of core and cladding is very small. The optical fiber acts as a wave guide and transmits the optical pulses towards the receiver, by the principle of total internal reflection. They work under the principle of total internal reflection from diametrically opposite walls. 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 following figure explains the parts of an optical fiber. It consists of a very thin fibre of silica or glass or plastic of a high refractive index called the core. At a particular angle of This creates a optimal waveguide for transmitting light. incident ray is completely reflected back in the water (or medium with higher The working principle of optical fiberis the transmission of the information in the form of light atoms otherwise photons. Fiber cables rated at 10 Gbps, 40 Gbps, and 100 Gbps are stand Depending upon the material composition of the core, there are two types of fibers used commonly. In optical fibre system transmission losses are as low as 0.1 db/km. 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 . Thus, the ray of light reaches the other end of the fibre after suffering repeated total internal reflections along the length of the fibre. Your email address will not be published. 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. 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 … (3) Light travels down the fibre. Where θi = angle of incidence at the air-core 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 … Hence the communication A fundamental optical parameter one should have an idea about, while studying fiber optics is Refractive index. A bunch of such optical fibres forms optical fibre cable. Please clarify whether the core is solid or hollow. Let ∅ be the angle of incidence at the core-cladding interface negligible loss of energy. The largest possible value of NA is unity, Numerical Aperture for Step Index Fibre in Terms The device or a tube, if bent or if terminated to radiate energy, is called a waveguide, in general. 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. All of ray refrect when the ray enters large angle of incidence when outside substance has small refractive index. 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. If the angle Hence, more protection is needed than copper ones. Thus they can be twisted and bent easily. The light detector receives the optical pulses and converts them into electrical pulses 5. Light losses in fibres Fibre is a transparent cylinder made of a dielectric. The end of the rod is pulled at a constant rate to form a thin fibre containing the core and the cladding. The optical fibers have many applications. Optical fibers are also unaffected by electromagnetic interference. The core and the cladding, both are made up of different materials. A fiber made of a core and cladding with two reflective indices near and clad is called step index. Used in hospitals, schools, and traffic management systems. The physical advantages of fiber optic cables are −. Previous Topic: Communication Channels: Wires, Cables, Optic Fibres. Fiber optics support a higher capacity. Atul Agnihotri (Summer Training In-charge) 2. The digital communication techniques discussed so far have led to the advancement in the study of both Optical and Satellite communications. The light propagation, along a waveguide can be described in terms of a set of guided electromagnetic waves, called as modesof the waveguide. Fibre optic fibres do not carry high voltages or current. An optical fibre is a thin, transparent fibre, usually made of glass or plastic, for transmitting light. 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. Principle and major types The optical fibre consists of the core and the cladding, which have different refractive indexes. These cables are formed of two materials with different refractive indices. The transmission bandwidth of the fiber optic cables is higher than the metal cables. Graded-index fiber − The core refractive index is made to vary as a function of the radial distance from the center of the fiber. At the other end, the ray suffers refraction and emerges out of the optical fibre. The core is enclosed by a cover of glass or plastic called cladding. Although optical fiber appears to be only a simple thread, it is actually composed of two structures similar to water and air. Characteristics of Optical Fibre: It has a large bandwidth. 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