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Advantage of graded index fiber over step index fiber?
A graded index multimode fiber will transmit 800 modes, and has a varying refractive index. A step index multimode will transmit 228 modes.
What is the difference between step index and graded index optical fiber?
1. Step index fiber is of two types viz; mono mode fiber and multi mode fiber. Graded index fiber is of only of one type that is multi mode fiber. 2. The refractive index of the core of the step index fiber is constant through out the core. The refractive index of the core of the graded index fiber is maximum at the center of the core and then it decreases towards core-cladding interface. 3. Number of modes for step index fiber N = V2/2, where V is cut off frequency or normalized frequency or V- number Number of modes for graded index fiber is N = V2/ 4. 4. V number can be less that 2.405 or more that 2.405 for step index fiber V number is always more than 2.405 for graded index fiber. 5. Step Index Fiber is a fiber in which the core is of a uniform refractive index and there is a sharp decrease in the index of refraction at the cladding. Graded Index Fiber is a type of fiber where the refractive index of the core is lower toward the outside of the fiber. It bends the rays inward and also allows them to travel faster in the lower index of refraction region. This type of fiber provides high bandwidth capabilities.
What is the significance of normalized frequency in optical fiber?
If V is less than 2.405 then the fiber is mono mode but if V is greater than 2.405 then fiber is multimode. V number is also related with the number of modes is the fiber as: N = V2/ 2 for step index fiber and Number of modes for graded index fiber is N = V2/ 4.
Material dispersion equation with curve?
Material dispersion in a step index fiber is given by:Dispersion = -(length/c)*((DELTA_wavelength)/wavelength)*(2nd derivitive of n1 wrt wavelength)c = speed of lightDELTA_wavelength/wavelength is usually given as a percentage2nd derivitive of n1 wrt wavelength can be found using a graph.Since n1 is a function of the fiber you're using you must obtain a graph of dispersion for that particular material. I have a graph for glass silica. Let me know if you need it.
What are optical fiber?
Fiber optics are cables that are used to transmit data at the speed of light. This uis especially popular with Verizon FiOS services. for details on fios go to www.whyisfiosbetter.viviti.com
The dependence of wave speed and index of refraction on wavelenght is called?
Dispersion.
Why does dispersion not occur in hollow prism?
bcz there is no difference in refractive index during proagation
What are the three categories of data communication?
Fiber Types & Modes of TransmissionIn fiber optics, the term "mode" refers to a stable propagation state of light down the fiber. Fibers can have any number of stable propagation states (modes), giving rise to two basic types of optical fibers, multimode and singlemode. Multimode obviously refers to a fiber that has many modes of propagation, while a singlemode, by design, only has one. Whether a particular fiber is multimode or singlemode depends on the fiber geometry, core/clad refractive indices, and the wavelength of operation. Multimode fibers can be further broken down into two subcategories, step-index and graded-index. Each type has distinctive advantages and disadvantages, which will be discussed below in more detail.Step-Index Multimode Fiber This was the first fiber type to find practical application, and continues to be in wide use today. A step-index multimode fiber allows the light to travel at many different angles within the fiber, thereby allowing many modes of propagation. The term "step" refers to the step function the refractive index takes at the core/clad interface.The advantages of a step-index multimode fiber are related to the relatively large core area and high numerical apertures. Both of these properties allow light to be easily coupled into the fiber. In turn, this allows the use of inexpensive termination techniques, low cost diodes, and high power handling capability. These fibers are therefore widely used in high power laser delivery applications (medical procedures, material processing), industrial process control links (factory automation), short distance data communications, and fiber sensors.A disadvantage to step-index multimode is bandwidth. Referring to the figure, the path the light takes down a step-index multimode fiber will be longer or shorter depending on the angle of propagation. This difference in path length causes the pulse of light to spread out during its journey down the fiber. This is known as modal dispersion (see Dispersion section). As one pulse spreads, it eventually interferes with the neighboring pulses, distorting the transmission signal. The longer the fiber length, the more severe this pulse spreading will become. However, this is only a problem in applications that require a coherent signal, as in communications links. Power delivery or sensor systems do not require coherent transmission and many data communication or industrial process control links are relatively short distances (less than 2km), allowing the widespread use of step-index multimode fiber.There is a wide selection of step-index multimode fiber available. Sizes vary from ~50 to >2000µm core diameters. Their construction can be silica or plastic cladding using silica, plastic, or liquid as a core. There are also applications with no core called hollow waveguides. The silica constructions allow lower attenuation, greater spectral range, higher power handling capability, and greater environmental range. Plastic fibers offer lower cost and greater flexibility, but are limited in transmission and environmental properties. Hollow waveguides are used principally in the IR.Polymicro offers a wide selection of step-index, multimode fibers, particularly for laser power delivery and stringent or harsh environmental conditions. Please refer to our data sheets.Graded-Index Multimode Fiber As the name implies, the refractive index of this fiber gradually decreases from the core out through the cladding, as opposed to the abrupt step change of step-index. Instead of taking a zigzag path down the fiber, the gradual change in refractive index directs the light in a sinusoidal path as previously illustrated. Since the light travels faster in a material of lower refractive index, the light traveling on the outer reaches of the graded region moves more quickly, thereby reducing the amount of pulse spreading. The result is a dramatic >25-fold increase in bandwidth over step-index multimode fibers.Graded-index is actually a compromise between step-index multimode and singlemode fibers, trading off bandwidth for ease of termination and light launch. The graded profile and smaller core increases bandwidth over step-index multimode, but the core sizes are still large enough for convenient termination and use of lower cost diodes. In more recent years, the components and techniques for terminating singlemode has improved dramatically, so graded-index has seen a decline in market share. However, graded-index remains a popular standard for use in medium distance (2-15km) data communication links.The most common core sizes for graded-index multimode fibers are 50, 62.5, and 100mm. These sizes have become industry standards. The construction is always silica core/silica clad based, with dopants (typically Ge, B, P, and F) used to adjust the refractive index in the graded profile. This fiber is used almost exclusively for medium distance data communication (local area networks), although it is sometimes used for fiber sensor systems. The smaller core area makes this fiber less useful for power delivery applications, however new special, larger core designs specifically for high power applications are available.Singlemode Fiber In singlemode fiber the core size is reduced to the point (5-10mm diameter) where only one mode, the primary mode, can be guided. This mode essentially travels straight through the fiber and thus is not subject to the pulse spreading seen in multimode fiber due to different path lengths. The net effect is a substantial increase in bandwidth since all the light is traveling at the same speed for the same distance. In addition, using the primary mode and higher operational wavelengths (1310 and 1550nm) results in very low attenuation. For these reasons, singlemode is the fiber of choice for long distance data and voice communication.Singlemode does experience some distortion of the signal, but this is due primarily to chromatic dispersion, which is variation in light speed due to the pulse not being purely monochromatic. This type of dispersion is very small when compared to the modal dispersion experienced in multimode fibers.Singlemode fiber typically consists of a silica core/silica clad construction with a step-index refractive index profile. The core and/or clad is doped to obtain the index difference between the core and clad. The core size, being very small, is more difficult and costly to terminate versus the multimode fibers, but for long distance systems this cost is acceptable. In contrast, the small core size does not allow a great deal of power input, and therefore this fiber is generally not suitable for power delivery and many sensor applications.
What is the Principle of optical fiber?
Fiber optic cables containing silica called filamentous crystal crystalline silica is actually the main component of these filaments heap on the inner wall can be attached to the wire with the wire bent over bent when the optical signal from the wire the optical signal to one input of the specular reflection on the surface of the silica on the principle of reflective transmission until it reaches the other end of the optical signal conductor recognizer so far. Fiber is divided into the following two categories: 1) transfer points modulo class Transfer points modulo class of single-mode fiber and multimode fiber. Single-mode fiber core diameter is small, at a given operating wavelength only in single-mode transmission, the transmission frequency bandwidth, transmission capacity. Multimode fiber is given in the operating wavelength, can be transmitted simultaneously to a plurality of mode optical fiber. Compared with single-mode fiber, multimode fiber transmission performance is poor. 2) refractive index distribution type Refractive index distribution type optical transitions can be divided into optical fiber and tapered optical fiber. Hopping optical fiber core refractive index and the refractive index of the protective layer is a constant. And a protective layer in the core of the interface, the refractive index changes stepwise type. Graded refractive index of optical fiber core increases as the radius decreases according to certain rules, and the protective layer of the core is reduced to the junction of the refractive index of the protective layer. Similar to the refractive index of the core changes parabola.
What is the normal dispersion of the refractive indices?
In which the index of refraction is higher for short wavelengths and lower for long wavelengths.
How will violet light react in the process of dispersion?
Violet light has a higher index of refraction than red or blue because it is a higher frequency wave. Violet light will have the largest angle of deviation during the process of dispersion.
Advantages of single step index fiber over multimode step index fiber?
The single step fiber mode tolerates high powered laser use and a high bandwidth in comparison to the multi-step which only allows for non-coherent light sources and lower bandwidth.
