Elective 5

Fiber Optic

2008-01-30T02:46:00.000-08:00

Fiber Optic Cable

An optical fiber' (or fibre) is a glass or plastic fiber designed to guide light along its length. Fiber optics is the overlap of applied science and engineering concerned with the design and application of optical fibers. Optical fibers are widely used in fiber-optic communication, which permits transmission over longer distances and at higher data rates than other forms of communications. Fibers are used instead of metal wires because signals travel along them with less loss, and they are immune to electromagnetic interference. Optical fibers are also used to form sensors, and in a variety of other applications.

Light is kept in the "core" of the optical fiber by total internal reflection. This causes the fiber to act as a waveguide. Fibers which support many propagation paths or transverse modes are called multimode fibers (MMF). Fibers which support only a single mode are called singlemode fibers (SMF). Multimode fibers generally have a large-diameter core, and are used for short-distance communication links or for applications where high power must be transmitted. Singlemode fibers are used for most communication links longer than 200 meters.

Joining lengths of optical fiber is more complex than joining electrical wire or cable. The ends of the fibers must be carefully cleaved, and then spliced together either mechanically or by fusing them together with an electric arc. Special connectors are used to make removable connections.

History of Fiber Optic Cable

The light-guiding principle behind optical fibers was first demonstrated by Daniel Colladon and Jaques Babinet in the 1840s, with Irish inventor John Tyndall offering public displays using water-fountains ten years later. Practical applications, such as close internal illumination during dentistry, appeared early in the twentieth century. Image transmission through tubes was demonstrated independently by the radio experimenter Clarence Hansell and the television pioneer John Logie Baird in the 1920s. The principle was first used for internal medical examinations by Heinrich Lamm in the following decade. In 1952 physicist Narinder Singh Kapany conducted experiments that led to the invention of optical fiber, based on Tyndall's earlier studies; modern optical fibers, where the glass fiber is coated with a transparent cladding to offer a more suitable refractive index, appeared later in the decade.[1] Development then focused on fiber bundles for image transmission. The first fiber optic semi-flexible gastroscope was patented by Basil Hirschowitz, C. Wilbur Peters, and Lawrence E. Curtiss, researchers at the University of Michigan, in 1956. In the process of developing the gastroscope, Curtiss produced the first glass-clad fibers; previous optical fibers had relied on air or impractical oils and waxes as the low-index cladding material. A variety of other image transmission applications soon followed.

In 1965, Charles K. Kao and George A. Hockham of the British company Standard Telephones and Cables were the first to suggest that attenuation of contemporary fibers was caused by impurities, which could be removed, rather than fundamental physical effects such as scattering. They speculated that optical fiber could be a practical medium for communication, if the attenuation could be reduced below 20 dB per kilometer.[2] This attenuation level was first achieved in 1970, by researchers Robert D. Maurer, Donald Keck, Peter C. Schultz, and Frank Zimar working for American glass maker Corning Glass Works, now Corning Inc. They demonstrated a fiber with 17 dB optic attenuation per kilometer by doping silica glass with titanium. A few years later they produced a fiber with only 4 db/km using germanium oxide as the core dopant. Such low attenuations ushered in optical fiber telecommunications and enabled the Internet. Nowadays, attenuations in optical cables are far less than those in electrical copper cables, leading to long-haul fiber connections with repeater distances of 500 - 800 km.

The erbium-doped fiber amplifier, which reduced the cost of long-distance fiber systems by reducing or even in many cases eliminating the need for optical-electrical-optical repeaters, was co-developed by teams led by David Payne of the University of Southampton, and Emmanuel Desurvire at Bell Laboratories in 1986. The more robust optical fiber commonly used today utilizes glass for both core and sheath and is therefore less prone to aging processes. It was invented by Gerhard Bernsee in 1973 by Schott Glass in Germany.

In 1991, the emerging field of photonic crystals led to the development of photonic crystal fiber (Science (2003), vol 299, page 358), which guides light by means of diffraction from a periodic structure, rather than total internal reflection. The first photonic crystal fibers became commercially available in 1996. Photonic crystal fibers can be designed to carry higher power than conventional fiber, and their wavelength dependent properties can be manipulated to improve their performance in certain applications.

Purchase evaluation equipment or software

2008-01-18T19:28:00.000-08:00

Purchase equipment or some hardware and software needed in a certain company are good, but we have also to consider that every investment should be use in the company not on our personal interest. Because there are some employees especially in high rank, they made a decision for there on good or satisfaction on there self. And People tend to be attracted to risk. They buy international stocks. And they buy tech stocks - the riskiest of all (and about three times as risky as stocks in general). I don't know if people haven't seen a table like this before, or if they just don't want good-but-boring investments like timber or decent corporate bonds, for example. But when you take the time to compare the risk-reward ratios of different investments - in much the same way you would compare features of new luxury cars before purchasing - you give yourself a much clearer understanding of what to expect for your money. As we proved here, it's easy to find out just how much return you can expect…and just how many sleepless nights you'll have along the way. One more important thing to note: we only used 18 years worth of data in this chart, and that's probably not enough. If you just invested based on this table, you'd buy big U.S. stocks right now and shun small stocks, which could be a dangerous move. The table and the comparisons are only as good as the data used. And he investment decision (also known as capital budgeting) is one of the fundamental decisions of business management: managers determine the assets that the business enterprise obtains. These assets may be physical (such as buildings or machinery), intangible (such as patents, software, goodwill), or financial (see below). The manager must assess whether the net present value of the investment to the enterprise is positive; the net present value is calculated using the enterprise's marginal cost of capital.

A business might invest with the goal of making profit. These are marketable securities or passive investment. It might also invest with the goal of controlling or influencing the operation of the second company, the investee. These are called intercorporate, long-term and strategic investments. Hence, a company can have none, some or total control over the investee's strategic, operating, investing and financing decisions. One can control a company by owning over 50% ownership, or have the ability to elect a majority of the Board of Directors.“What Reward to Risk Ratio is Right for you? “The key message here is that, when you evaluate any investment, you've got to consider both expected RETURN and RISK. Most people, dreaming about big potential returns, forget about the second variable - RISK. Don't include yourself in that list. Before making an investment, ask yourself: "How much risk am I really taking, and what is my upside?" For me, personally, I like to have a three-to-one reward-to-risk ratio. If I can't potentially make three times whatever I have at risk in a stock, it's not worth it.

Ability to track and measure performance

2008-01-13T00:00:00.001-08:00

As a student, I agree with the “Ability to track and measure performance “or “
It’s important to set objectives and be able to measure your progress. Successful managers establish specific measurements that tell them and others how well the organization is doing and provide feedback that helps managers zero in on issues that will improve the organization’s performance.” Because as I experience in our school. All student must required to have there club. But depend to the student ability and performance. After we choose club organization, the instructor assign or student are the one who will give a practicum exam for individuals. The practicum exam or result are the evidence that we student are have the ability or performance to be one of the club organization we choose. And help this organization to be more improved than last year. With the simple story, obviously the assign instructor or student trying to test if that student are sufficient to there club, cause I believe the every student have there own ability but in different fields. That’s way we need to have a test the ability of individuals. But there are lots of students missed judging by other students. Not only student but there are some instructor. That they don’t know, every people have his own talent. Just like managers, it is also important to track or measure how they work, ask comments to others and be guided with the others. So that they will know how they work, are they being good there employee, are they need to enhance there self or what is lacking to theme. Because I believe that to others we can ask anything about our self or how you manage theme as a manager of a certain company. With that technique, not only your self will improve but also others will respect you as the manager not only manager but as loyal friend theme also.

The Difference of CSMA/CD and CSMA/CA

2007-12-13T23:36:00.001-08:00

CSMA/CD - a transmitting data station that detects another signal while transmitting a frame, stops transmitting that frame, transmits a jam signal, and then waits for a random time interval (known as "backoff delay" and determined using the truncated binary exponential backoff algorithm) before trying to send that frame again.

CSMA/CA - a station wishing to transmit has to first listen to the channel for a predetermined amount of time so as to check for any activity on the channel. If the channel is sensed "idle" then the station is permitted to transmit. If the channel is sensed as "busy" the station has to defer its transmission. This is the essence of both CSMA/CA and CSMA/CD. In CSMA/CA (LocalTalk), once the channel is clear, a station sends a signal telling all other stations not to transmit, and then sends its packet. In Ethernet 802.11, the station continues to wait for a time, and checks to see if the channel is still free. If it is free, the station transmits, and waits for an acknowledgment signal that the packet was received.

This is my first blog...

2007-11-16T02:24:00.000-08:00

Hello!!!! Have a nice day....