Stepped-index type

Fig. 3. Types of optical fiber (a) multimode stepped index, (b) multimode graded index, and (c) single-mode stepped index.

There are two major types of planar waveguides - those with a graded index and those that are step-indexed, as shown in Fig. 4. Waveguides can be composed of any optically transparent material such as glassy materials and polymers, depending on their structure. 

We mentioned above three types of optical fibers step index single mode, step index multimode, and gradient index multimode. The last two types can carry more light that the step index single mode fiber. Lightness is a very important feature. Among the important features for such a system are the following (Oare, 1995) ... 

Figure 7.9 Refractive index profiles of three common types of optical glass fiber multimode step index, multimode graded index, and single mode.

FIGURE 4-1 Refractivity and core diameter ranges for three types of optic fibers, (a) Multi-mode step-index optic fiber, (b) Multi-mode gradient-index optic fiber, (c) Single model step-index optic fiber. 

The production of activated carbon extrudates by steam activation does not follow the general scheme of Fig. 8. In this case, after crushing the raw mato ial is first devolatilized at high temperature and then finely pulverized, resulting in a powdered char. The powdered char is then mixed with appropiate binders to form a paste with lubricant properties, which is extruded. Normally several binders are used to form the paste because they each have different tasks a) to provide lubricant properties to allow the extrusion of the paste b) to transform the wet extrudates into hard and consistent short cylinders during the drying step (low temperature binder), and c) to act as a high temperature binder in the activation step. The type and composition of the hinder is a matter for further research, since the final hardness and abrasion index is dependent on the binders. Consequently, it is not unusual for them to be a mixture of three binders, each with a specific mission. 

Figure 14.32 Types of optical fibre (a) stepped index fibre, (b) graded index fibre and (c) monomode fibre...

Since all commercially available POF have been of the step-index (SI) type, the modal dispersion limits the possible bit rate of POF links to less than 100 megabit per second (Mb/s). Because of this, it has been thought that POF cannot be utilized for high speed transmission medium. Recently, however, we proposed a large core, low loss, and high bandwidth graded-index polymer optical fiber (GI POF) (7,2) for the first time and we confirmed that 2.5 Gb/s signal transmission for 100 m distance was possible in the GI POF (2,5). 

Material Dispersion. The material delay distortion for propagation of a pulse in the step-index (SI) qie and single-mode type optical fiber can be obtained from the following equation(P) ... 

A specific number of modes are allowed to propagate down the length of a fiber. When the core and cladding each have a constant refractive index across their cross sections, but the core refractive index is different than the cladding refraction index, then they behave like an optical waveguide. This is referred to as step index and in this fiber type, only a specific number of modes can propagate. 

This section provides a brief review of the types and characteristics of optical fiber amplifiers, step index fiber waveguides, and fiber components and often used fiber lasers. The effect of the various fiber component characteristics on fiber laser performance is highlighted. 

Figure App. 15.1 illustrates the steps required to accomplish a three-stage countercurrent wash in a laboratory test. It is easiest to understand the principle behind this test by visualizing a continuous horizontal vacuum belt filter in operation (an indexing type is referred to here but the same applies to the models with continuous belt movement). The slurry enters the feed zone and the cake is formed (Step 1). The cloth indexes (follow Leaf C in the figure) and the formed cake move into the first wash area (Step 2). Another...

Figure A.1 Ray trajectories through basic types of optical fibers, (a) Single-mode fiber, (b) Step-index multimode fiber, (c) Graded-index multimode fiber.

There are basically two types of optical communications fiber design, each having many variations. The first type, called step-index fiber, is similar in construction to that described in Sec. 6.6 for traditional fiber optics, with several key differences (1) Communications fiber dimensions are generally much smaller. (The outside diameter is now a standard 125 p.m the core diameter can be as small as about 8 /xm.) (2) The refractive index difference (An) between core and cladding is much smaller, on the order of 1 percent, or less. (3) Much greater precision is required for the critical dimensions, including core concentricity within the fiber. 

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