The Optical Time Domain Reflectometer Essay Example for Free

The Optical Time Domain Reflectometer Essay In fiber optic networks, OTDR (Optical Time Domain Reflectometer) is an opto-electronic instrument used to characterize an optical fiber. Unlike power meters OTDR does not measure loss, but instead implies it by looking at the backscatter signature of the fiber. Generally, OTDR are used to determine the loss of any part of a system, the length of the fiber and the distance between any points of interest. Most of the light which is sent to the fiber can be detected at the other end, but a part of it is always absorbed or scattered. Absorption and scattering are caused by imperfections of fiber, small grains of dirt, for instance. Scattering means that light is not absorbed but it is just sent in different angle after it hits small particles in optical fiber (Figure 1). Some of the light is scattered to the direction it came from. This is called backscattering. Backscattering forms the basis to the use of the optical time domain reflectometry. Figure 1 Rayleigh –scattering in optical fiber Optical time domain reflectometry is based on scattering and reflections. OTDR sends an optical pulse to the fiber and measures the received backscattering. The signal which is received consists naturally only of scattering and reflections of pulse which was sent. By interpreting signal as a function of time OTDR can draw an attenuation of a fiber as a function of distance. Theory of the OTDR Optical time domain reflectometry measures backscattering as a function of time and graph is then drawn as a function of distance (Figure 2). The graph represents the power of signal which the detector of the OTDR receives. The graph of fiber probed by OTDR consists of two spikes with gradually decreasing line between them. The line between spikes is decreasing because the received signal is decreased as a function of distance in accordance with attenuation coefficient of fiber. At the both ends of fiber reflection is large (Fresnel reflection) which creates spikes to the graph. Length of the fiber can therefore be measured from the width of the graph. Figure 2 OTDR signal as a function of distance An OTDR trace is a graphical representation of optical changes or events on a fiber. An event could be a splice, optical connector, a bend, a break, or just normal backscattered light from the fiber itself. In the OTDR trace faults for instance, are shown as a drop in the power of received signal (Figure 3). Size of a drop depends on an amount of power that is lost due to the component. The lost power represents of course the attenuation of component. Components and faults in fiber are either reflective or nonreflective. Reflective components create a spike to the graph of OTDR the same way as the both ends of fiber do. With nonreflective components there are no spikes because no excess light is reflected back. In most cases reflective attenuation is caused by connectors or other passive components and nonreflective attenuation is usually caused by fusion splice or similar fault in fiber. Figure 3 Attenuation of different faults Figure 4 OTDR Trace Information The slope of the OTDR trace shows the attenuation coefficient of the fiber and is calibrated in dB/km by the OTDR (Figure 4). Whereby, The height of that peak will indicate the amount of reflection at the event, unless it is so large that it saturates the OTDR receiver. Then the peak will have a flat top and tail on the far end, indicating the receiver was overloaded. Sometimes, the loss of a good fusion splice will be too small to be seen by the OTDR. Thats good for the system but can be confusing to the operator. It is very important to know the lengths of all fiber in the network so that the operator is not confused by unusual events. Reflective pulses show the resolution of the OTDR. Two events which are closer than the pulse width cannot be seen. Generally longer pulse widths are used to be able to see farther along the cable plant and narrower pulses are used when high resolution is needed, although it limits the distance the OTDR can see. The Dead Zone Dead zones originate from reflective events (connectors, mechanical splices, etc.) along the link, and they affect the OTDR’s ability to accurately measure attenuation on shorter links and differentiate closely spaced events, such as connectors in patch panels, etc. When the strong optical reflection from such an event reaches the OTDR, its detection circuit becomes saturated for a specific amount of time (converted to distance in the OTDR) until it recovers and can once again measure backscattering accurately. As a result of this saturation, there is a part of the fiber link following the reflective event that can not be â€Å"seen† by the OTDR. Analyzing the dead zone is very important to ensure the whole link is measured. Two types of dead zones are usually specified: 1. Event dead zone: This refers to the minimum distance required for consecutive reflective events to be â€Å"resolved†, i.e., to be differentiated from each other. If a reflective event is within the event dead zone of the preceding event, it will not be detected and measured correctly. Industry standard values range from 0.8 m to 5 m for this specification. Figure 5 Common OTDR with 3 m event dead zone 2. Attenuation dead zone: This refers to the minimum distance required, after a reflective event, for the OTDR to measure a reflective or non-reflective event loss. To measure short links and to characterize or find faults in patchcords and leads, the shortest possible attenuation dead zone is best. Industry standard values range from 3 m to 10 m for this specification. To overcome the problem of dead zones, usually a patchcord of about 100 m is added at the beginning of the system. As a result, all lauch dead zone problems have finished before the fiber (which is to be tested) is reached. Ghosts When testing short cables with highly reflective connectors, it is likely to encounter ghosts like in Figure 6. These are caused by the reflected light from the far end connector reflecting back and forth in the fiber until it is attenuated to the noise level. Ghosts are very confusing, as they seem to be real reflective events like connectors, but will not show any loss. If a reflective event in the trace is found at a point where there is not supposed to be any connection, but the connection from the launch cable to the cable under test is highly reflective, look for ghosts at multiples of the length of the launch cable. Figure 6 OTDR Ghosts Resolution of the OTDR Consider that light travels 1 m every 5 ns in the fiber, so a pulsewidth of 100 ns would extend for a distance of 20 m. When the light reaches an event, such as a connector, the light is reflected. The reflection appears to be a 20 m pulse on the OTDR. However, if two events are separated by a distance of 10 m or less (Figure 7), the two reflections will overlap and join up in returning to the OTDR. Figure 7 Thus the OTDR will display the two events as one event and the loss at each event is not detected, instead the sum of losses at both events will be shown on the OTDR. Choosing a shorter pulsewidth may give a better resolution but in turn resulting a low energy content (causing shorter detection range). Besides using a shorter pulse which will provide the required range, a tool that is called a â€Å"visual fault locator† can help too. The visual fault locator injects a bright red laser light into the fiber to find faults. If there is a high loss, such as a bad splice, connector or tight bend stressing the fiber, the light lost may be visible to the naked eye. This will resolve event which is close to the OTDR or close to another event that are not resolvable to the OTDR. The limitation of this tool is about 4 km.

Affirmative Action Will Build a Strong Nation Essay -- affirmative act

Affirmative Action Will Build a Strong Nation Affirmative Action: often upon hearing this word, one will start thinking about quotas and reverse discrimination. However, contrary to this misconception, affirmative action is actually a policy that dictates that employers attempt to find diverse employees by exploring untraditional sources of labor. The goal of affirmative action is to create a work force that mirrors the population of the nation both in gender and in ethnicity (Hanmer 8,10). Affirmative action is necessary to give all Americans an opportunity to be successful and to counteract the discrimination that still exists in modern society. Affirmative action is not only morally justifiable, but it is also socially and economically preferable in order to improve our society. The United States’ government first implemented affirmative action to overcome some of the clear differences in living conditions between people of different genders and races. Unfortunately, these differences still exist and eliminating affirm ative action now would be premature for our nation. Affirmative action is essential to compensate for the fact that women and minorities receive fewer opportunities to succeed. Even after laws were passed to end institutionalized racism, the white males who owned the businesses and held the best jobs before continued to own the businesses and hold the best jobs. While legal equality may have been achieved, the nation was nowhere near having true social equality. As President Lyndon B. Johnson stated when he first started affirmative action, â€Å"This is the next and the more profound stage of the battle for civil rights. We seek not just freedom but opportunity. We seek not just legal equity but human abi... ...., William. â€Å"Give Affirmative Action Time to Act.† AAD Project. 1 Dec. 2000. University of California Santa Barbara, Department of English. 19 Feb. 2002 http://aad.english.ucsb.edu/docs/darity.html>. Hanmer, Trudy J. Affirmative Action: Opportunity for All?. Hillside, NJ: Enslow Publishers, Inc., 1993. Mask, Susan. â€Å"Countering the Myths: A Proponent’s Point of View.† University of Iowa, Office of Affirmative Action. 25 Feb. 2002 http://www.uiowa.edu/~oaa/counteri.htm>. Plous, Scott. â€Å"Ten Myths About Affirmative Action.† Journal of Social Issues. 52.4 (1996): 25-31. Pressley, Sue Anne. â€Å"Texas Campus Attracts Fewer Minorities.† Washington Post. 28 Aug. 1997, http://www.washingtonpost.com/wp-srv/politics/special/affirm/stories/ aa082897.htm>. Supplier Diversity. Nike. 17 Mar. 2002. http://www.nikebiz.com/diversity/supplier.shtml>.

Dear Stella

Dear Stella, I hope this letter finds you well. I am sorry about leaving so abruptly, but I was called away on urgent work. I have been sent to Crythin Gifford by Mr. Bentley to attend the funeral of Mrs. Alice Drablow, I also need to sort though all of her legal documents. Mrs. Drablow lived in a strange little house called Eel Marsh House. To get out to the house you must cross the Nine Lives Causeway, it is only accessible during low tide, otherwise it is covered by water, and impassable. The house is very strange, all on it's own on a small island separated from the rest of the main land. At first I thought it to be quite beautiful but it has a scary if not dark side to it. Even Mrs. Drablow was a bit strange, she lives alone and no one from the village will speak of her. When I arrived Mr. Daily, the local landowner, took me to the Gifford Arms where I have been staying. I went to the funeral of Mrs. Drablow, on the way there I saw some school children and they had strange white pasty faces. When I arrived I noticed that there were very few people there. There was a woman in black clothes with a pasty white face, which I saw on the way back to the village and again on Eel Marsh Island. After the funeral of I went to Eel Marsh house, to start work. Mr. Keckwick took me across the causeway on a horse and trap. When we arrived at Eel Marsh House Keckwick left me and said he would return at five to collect me. I looked around the island; there is an old graveyard with some ruins of a small abbey. The names on the gravestones were all undecipherable because they were covered with various fungi's. While looking around the graveyard I saw the mysterious Woman in Black, a cold feeling came over me like nothing I had ever felt before, but before I could approach her she ducked away under a headstone and disappeared. I don't think you should worry about me I'm fine and I'm not worried about her. She was probably a figment of my imagination; the marsh mist was quite dense. After that went in to the house and I started work opening all the windows, to get some light. I searched thought the rooms to see what was in side the house. It has an old musty smell, all the furniture is old, and made of strong wood. It was about four, so I decided I would walk back to Crythin Gifford, Keckwick wouldn't be back until five and the exercise would be good for me. As I started to walk along the causeway I noticed that it was getting darker and darker and the mist was drawing in, the sea mist was thick and salty. The further I got from the house the better I felt, but soon I couldn't see it any more because of the mist. I thought about turning back but I would soon meet Keckwick and he could take me the rest of the way. The mist was soon playing tricks on my sight and hearing, I could hear a pony and trap coming a long the road to the causeway, and it went silent. I then heard noises of screaming like someone was drowning, I thought this was my imagination, I didn't know how far it was to the other side of the causeway and the water was rising fast so I decided to turn back and head for the house. When I got back I was very worried and I was shaking. I sat down in one of the old musty chairs and had a drink, I must have fallen asleep because when I awoke someone was knocking on the door, when I opened it I saw Keckwick and the pony and trap. They were normal, still alive; it must have been my imagination about him drowning. He apologized for not coming to pick me up but he was unable to because of the sea mist, I was unlucky. I hope that everything in London is fine. There is no need for you to come down to Crythin Gifford, because I should be returning soon, I will go back to Eel Marsh House today and stay for a couple of days to finish all the work and send anything important back to Mr. Bentley. Hope to see you very soon. Yours Lovingly, Arthur

Essay The Golden Ratio - 995 Words

The Golden Ratio Certain pictures, objects, and animals appeal to the human mind more than others. Proportions and images of symmetry often contribute to our fascination with them. Often, when examined carefully, you may find a common â€Å"coincidence† between man made objects and those found naturally in nature. This fluke, however, may be used to ascertain various mathematical relationships between these objects. This paper will introduce the golden ratio and weigh its significance on math, art, and nature. 1.6180339887†¦. has been given many names varying from the â€Å"golden ratio† first coined by the Greeks, to the â€Å"golden rectangle† and â€Å"golden section†, â€Å"phi† named after Phidias a renowned Greek sculptor, as well as the â€Å"divine†¦show more content†¦The definitive polymath, he had almost too many gifts, including superlative male beauty, a splendid singing voice, magnificent physique, mathematical excellence, scientific daring†¦ (Beckett, 117) He studied at various places including Milan and Florence and the Vatican. It is in these cities that he became famous. He masterfully uses the golden ratio in the Mona Lisa framing her head as well as the rest of her body parts in exact proportion to the golden rectangle. Furthermore, he goes on in such works as the Vitruvian Man and Virgin and Child with St. Anne to incorporate the golden rectangle into everything he possibly can. He was by no means enthralled in art. Instead, his great passions were mathematics and the natural world, and he compiled volumes of detailed drawings and notes on anatomy, botany, geology, meteorology, architectural design, and mechanics. (Stokstad, 693) Toward the end of his life math, particularly the golden ratio, began to dominate everything he created. Leonardo da Vinci died in 1519. Another painter that used, primarily, golden rectangles was Piet Mondrian. In, Composition with Gray and Light Brown virtually every rectangle has the â€Å"pleasing† dimensions. Still, more possibilities abound. It has been proven that famous composers such as Bach, Beethoven and Bartok have used the golden ratio between intervals of their masterpieces. (FibonacciShow MoreRelatedGolden Ratio Essay765 Words   |  4 Pages(Peter,1971) From the Egyptians and Greek we have the Golden Ratio that was and is used for construction of buildings and in artwork. This essay will discuss the relation and use of science in art of the Renaissance, Baroque, and Rococo periods. The Golden Ratio Defined: The Golden Ratio. Throughout history, the ratio for length to width of rectangles of 1.618 has been considered the most pleasing to the eye. This ratio was named the golden ratio by the Greeks. In the world of mathematics, the numericRead MoreTaking a Look at the Golden Ratio782 Words   |  3 PagesGolden Ratio is found by dividing a line into two parts so that the longer part divided by the smaller part equals the whole length divided by the longer part. Golden ratio is very similar to pi because it is an infinite number and it goes on forever. It is usually rounded to around 1.618. The formula for golden ratio is a/b = (a+b)/b. It has been around for a long time so it is not known who made up the golden ratio. Since the golden ratio is used all around the world it is known in many names suchRead More Use of the Golden Ratio in Our World Essay595 Words   |  3 Pagesnumber from the sum of the previous two. This sequence of numbers is called the Fibonacc i Sequence. The Fibonacci numbers are interesting in that they occur throughout both nature and art. Especially of interest is what occurs when we look at the ratios of successive numbers. The Fibonacci numbers play a significant role in nature and in art and architecture. When you construct a set of rectangles using the sequence (1, 1, 2, 3, 5, 8, 13, 21,), a design found in nature is revealed: Next, whenRead MoreBeauty: Golden Ratio on Human Face Essay731 Words   |  3 PagesThe golden ratio can be seen in anywhere. It is also captured in many books and articles. It is also aesthetically shown in literature, art and ancient architectural buildings. The golden ratio can be seen in the way trees grow, in the ratios of both human and animal bodies. The ratio is approximately 1.618. The golden ratio is only can be seen by the one of the most complex organ in our body and it can be directly seen. The golden ratio has been discovered and used since ancient times. Our eye analyzesRead MoreArt and Math: Golden Ratio and the De Divina Proportione659 Words   |  3 Pagestools such as the Golden Ratio and the De Divina Proportione have helped shape the art we know today. Famous artists and mathematicians such as Piero De Francesca, Polykleitos, and M. C. Escher are the founders of the amazing works of art we are familiar with. Even modern day mathematics has given art a new fo rm, with Fractal Art. Without math, some of the art we have today would not exist. In the ancient times, the Golden Ratio was the most used mathematical tool. The Golden Ratio is a term usedRead MoreDebussys use of the Fibonacci sequence Essay1403 Words   |  6 PagesMusic An Analysis of Debussy’s Nocturne Math has been associated with music for many years, particularly that of the Fibonacci sequence and the Golden Ratio. In Debussy’s Nocturne, composed in 1892, I look into the use of the Fibonacci sequence and the Golden Ratio. Previously it has been noted that composers used the Fibonacci sequence and the Golden Ratio in terms of form, however in my analysis I look into the use of it in terms of notation as well. I will explore how the idea of Sonata form isRead MoreMathematics and Music: The Collision of Science and Art Essay1735 Words   |  7 Pagesare: how musical scales can be made using Fibonacci ratios, the Golden Ratio’s relationship with music, equal temperament, where else the Fibonacci numbers occur in music, the exponential nature of octaves, and how exposure to music helps ones understanding of math, and vice versa. Exploration An interesting connection that music has with mathematics is the presence of Fibonacci ratios in musical frequencies. To understand what exactly these ratios are we must first understand; what is the set ofRead MoreMathematics: The Fibonacci Sequence1323 Words   |  5 Pagesmust find the second term and so on. Golden Ratio In mathematics, two quantities are in the golden ratio if their ratio is the same as the ratio of their sum to the larger of the two quantities. The Golden Ratio can be used not only for Fibonacci Numbers, but also for all the other everyday numbers. When you take any two successive Fibonacci Numbers, their ratio is very close to the Golden Ratio, which is approximately 1.618034†¦ The Golden Ratio works for numbers other than the one’s inRead MoreMathematical and Musical Harmony1308 Words   |  6 Pagescommonly considered to do, but that there are connections and similarities between them, which may explain why some musicians like mathematics and why mathematicians frequently love music. Music is mathematical because the Fibonacci numbers and the golden section exist in musical compositions. The questions of tone and tuning are one aspect in which mathematical thoughts enter the world of music. However, music—at least in a modern perception—does not only consist of notes and harmony. More importantRead MoreThe Golden Mean in Anatomy965 Words   |  4 PagesThe Golden Mean in Anatomy The Golden Mean is a mysterious number that has been found in plants, humans, art and even architecture. It was first discovered and studied by ancient mathematicians in Egypt a very long time ago. In the study of mathematics one realizes that many patterns often occur. None have been more relevant or fascinating that the golden ratio. The golden ratio has many names and is often referred to as the golden section, golden mean, golden proportion and golden cut. The golden