Fiber Optics Essays (4499 words) - Optical Fiber, Fiber Optics

Fiber Optics Fiber optics produced by special methods from silica glass and quartz which replaced copper wire is very useful in telecommunications, long distance telephone lines and in examining internal parts of the body (endoscopy). Equipment for photography is available with all current fiber-optic endoscopes. Through a process known as total internal reflection, light rays beamed into the fiber can propagate within the core for great distances with remarkably little attenuation or reduction in intensity. In general, the methods of fiber production fall into three categories; (a) the extrusion method for synthetic fibers; (b) hot drawing of fibers from molten bulk material through an orifice; and (c) drawing of uncoated, coated and multiple fibers from assemblies of rods and tubes fed through a hollow cylindrical furnace. Three forms of fiber optics components have been proposed for the improvement of the image quality, field angle and photographic speed of various types of optical systems. These fiber optics elements, in the form of a field flattener, a conical condenser and distortion corrector, can be used separately or combined into a single unit called a "Focon". BOAZ? ?NVERSTES MAKNA M?HENDSL DEPARTMANI MALZEME DERS D?NEM PROJES YAZ OKULU 2000 ?ZET G?n?m?zde bakr tellerin yerini alan silikon camndan ve kristalinden ?retilen fiber optikler, telekom?nikasyonda, uzun mesafeli telefon hatlarnda ve insan v?cudunun i? ksmlarn inceleyen endoskopilerde kullanlmaktadr. Fotoraf ekipmanlarnda da b?t?n fiber-optik endoskoplara kullanlmaktadr. Tam i? yansma olarak bilinen ilem yoluyla, fiberin i?inde toplanan k nlar, uzun mesafeler boyunca iddetinde kk bir azalma ve bozulmayla yol alabilmektedir. Genellikle, fiber ?retimleri kategoridedir; Sentetik fiber ?retiminde dna ?karma methodu; Erimi d?kme maddelerden azlarna doru oluan fiberlerin scak ?izimleriyle, kaplanm,kaplanmam veya kark fiberlerin ?izimleriyle. ?eit olan fiber optik par?alar; g?r?nt? kalitesini, ?eitli optik sistemlerdeki alan a?s ve fotografik hzlar gelitirmek i?in dn?lm?t?r. Bu fiber optik elemanlar; alan d?zletirici, konik younlatrc ve sapma d?zenleyici ekillerindedir ve ayr veya "Focon" ad verilen ?nite i?in birlemi olarak kullanlabilirler. LIST OF FIGURES Figure 2.1 Photograph of the earliest bundle of uncoated aligned fibers Page 7 Figure 3.1 Core of a step index fiber Page 8 Figure 3.2 Schematic diagram of a typical fiber drawing Page 9 Figure 3.3 Preform manufacturing apparatus used in Silica-Quartz Page 11 Figure 3.4 Comparison of static,dynamic and spitial filtering imagery Page 12 Figure 4.1 Field flattener system of photography Page 13 Figure 4.2 Showing the image transmission through a conical fiber bundle Page 14 Figure 4.3 Fiber optics distortion correctors Page 14 Figure 4.4 Limiting resolution of Focon system Page 15 Figure 5.1 Single lens reflex camera Page 16 TABLE OF CONTENTS 1. INTRODUCTION 2. HISTORY OF FIBER OPTICS 3. WHAT IS FIBER OPTICS? 3.1 WHAT IS SILICA? 3.2 WHAT IS QUARTZ? 3.3 WHAT IS ENDOSCOPIC PHOTOGRAPHY? 4. ENDOSCOPIC PHOTOGRAPHY ELEMENTS 4.1 FIELD FLATTENER 4.2 CONICAL CONDENSER 4.3 DISTORTION CORRECTOR 4.4 FOCON RESOLUTION 5. ENDOSCOPIC PHOTOGRAPHY TECHNIQUES 5.1 COLOUR PHOTOGRAPHY WITH FIBRE-OPTIC ENDOSCOPES 5.2 CINE- ENDOSCOPY 5.3 CLOSED CIRCUIT COLOUR TELEVISION ENDOSCOPY 5.4 GASTRO-CAMERA EXAMINATION 6. CONCLUSION 7. REFERENCES 8. APPENDIX 1. INTRODUCTION The technology of fiber drawing for nonoptical applications is old and fairly standard. Very-small-diameter glass and quartz fibers were made as early as by Faraday. In the early stages of the production of glass fibers on an industrial scale, the main application of the fibers was envisaged in the textile industry. More recently, they have been used for insulation against sound, heat and electricity. Presently, very fine fibers are being made of materials such as glass, quartz, nylon, polystyrene, polymethylcrylate. Of these, glasses, quartz and plastics are preferred for optical use because of their higher visible light transmission, longer thermal working range, better surface characteristics and mechanical strength. Furthermore, it has been shown that glass fibers can have greater tensile strength than can be expected from the bulk material. 2. HISTORY OF FIBER OPTICS The conduction of light along transparent cylinders by multiple total internal reflections is a fairly old and well known phenomenon. It is entirely possible that grecian and other ancient glassblowers observed and used this phenomenon in fabricating their decorative glassware. In fact, the basic techniques used by the old Venetian glassblowers for making ?millifiore' form an important aspect of present-day fiber optics technology. However, the earliest recorded scientific demonstration of this phenomenon was given by John Tyndall in 1870. In demostration Thyndall used an illuminated vessel of water and showed that, when a stream of water was allowed to flow through a hole in the side of the vessel, light was conducted along the curved path of the stream. In 1951 when A.C.S. van Heel in Holland and H.H. Hopkins and N.S. Kapany studied on the transmission of images along an aligned bundle

John F. Kennedy and PT-109 in WWII

John F. Kennedy and PT-109 in WWII PT-109 was an 80-ft. patrol torpedo boat used by the US Navy during World War II. Commanded by Lt. John F. Kennedy, it was sunk by the destroyer Amagiri on August 2, 1943.   After the loss of PT-109, Kennedy went to great lengths to have his crew rescued. Nation: United StatesType: Patrol Torpedo BoatShipyard: Elco - Bayonne, NJLaid Down: March 4, 1942Launched: June 20, 1942Fate: Sunk August 2, 1943 Specifications Displacement: 56 tonsLength: 80 ft.Beam: 20 ft. 8 in.Draft: 3 ft. 6 in.Speed: 41 knotsComplement: 12-14 men Armament 4 x 21 torpedo tubes ( 4 x Mark VIII torpedoes)4 x .50 cal. machines guns1 x 20 mm cannon1 x 37 mm cannon Design Construction PT-109 was laid down on March 4, 1942, in Bayonne, NJ. Built by the Electric Launch Company (Elco), the boat was the seventh vessel in the 80-ft. PT-103-class. Launched on June 20, it was delivered to the US Navy the following month and fitted out at the Brooklyn Navy Yard. Possessing a wooden hull constructed of two layers of mahogany planking, PT-109 could achieve speeds of 41 knots and was powered by three 1,500 hp Packard engines. Driven by three propellers, PT-109 mounted a series of mufflers on the transom to reduce engine noise and allow the crew to detect enemy aircraft. Typically manned by a crew of 12 to 14, PT-109s main armament consisted of four 21-inch torpedo tubes which utilized Mark VIII torpedoes. Fitted two to a side, these were swung outboard before firing. In addition, PT boats of this class possessed a 20 mm Oerlikon cannon aft for use against enemy aircraft as well as two swivel mounts with twin .50-cal. machine guns near the cockpit. Completing the vessels armament were two Mark VI depth charges which were placed forward of the torpedo tubes. After work was complete in Brooklyn, PT-109 was dispatched to Motor Torpedo Boat (MTB) Squadron 5 in Panama. Operational History Arriving in September 1942, PT-109s service in Panama proved brief as it was ordered to join MTB 2 in the Solomon Islands a month later. Embarked aboard a cargo ship, it arrived at Tulagi Harbor in late November. Joining Commander Allen P. Calverts MTB Flotilla 1, PT-109 began operating from the base at Sesapi and conducted missions intended to intercept the ships of the Tokyo Express, which were delivering Japanese reinforcements during the Battle of Guadalcanal. Commanded by Lieutenant Rollins E. Westholm, PT-109 first saw combat on the night of December 7-8. Attacking a group of eight Japanese destroyers, PT-109 and seven other PT boats succeeded in forcing the enemy to withdraw. Over the next several weeks, PT-109 took part in similar operations in the region as well as conducted attacks against Japanese shore targets. During such an attack on January 15, the boat came under fire from enemy shore batteries and was holed three times. On the night of February 1-2, PT-109 took part in a large engagement involving 20 Japanese destroyers as the enemy worked to evacuate forces from Guadalcanal. With the victory on Guadalcanal, Allied forces began the invasion of the Russell Islands in late February. During these operations, PT-109 aided in escorting transports and provided security offshore. Amid the fighting in early 1943, Westholm became the flotilla operations officer and left Ensign Bryant L. Larson in command of PT-109. Larsons tenure was brief and he left the boat on April 20. Four days later, Lieutenant (junior grade) John F. Kennedy was assigned to command PT-109. The son of prominent politician and businessman Joseph P. Kennedy, he arrived from MTB 14 in Panama. Under Kennedy Through the next two months, PT-109 conducted operations in the Russell Islands in support of the men ashore. On June 16, the boat, along with several others, moved to an advanced base on Rendova Island. This new base became a target of enemy aircraft and  on August 1, 18 bombers struck. The raid sunk two PT boats and disrupted operations. Despite the attack, a force of fifteen PT boats was assembled in response to intelligence that five Japanese destroyers would be conducting a run from Bougainville to Vila, Kolombangara Island that night. Prior to departing, Kennedy ordered a 37 mm gun field mounted on the boat. Deploying in four sections, PT-159 was the first to make contact with the enemy and attacked in concert with PT-157. Expending their torpedoes, the two boats withdrew. Elsewhere, Kennedy patrolled without incident until spotting firing along the south shore of Kolombangara. Rendezvousing with PT-162 and PT-169, he soon received orders to maintain their normal patrol. Due east of Ghizo Island, PT-109 turned south and led the three-boat formation. Moving through the Blackett Straits, the three PT boats were spotted by the Japanese destroyer Amagiri. Turning to intercept, Lieutenant Commander Kohei Hanami bore down on the American boats at high speed. Spotting the Japanese destroyer at about 200-300 yards, Kennedy attempted to turn to starboard preparatory to firing torpedoes. Too slow, PT-109 was rammed and cut in half by Amagiri. Though the destroyer suffered minor damage, it safely returned to Rabaul, New Britain the following morning while the surviving PT boats fled the scene. Thrown into the water, two of PT-109s crew were killed in the collision. As the forward half of the boat remained afloat, the survivors clung to it until daylight. Rescue Aware that the forward section would soon sink, Kennedy had a float fashioned using a timber from the 37 mm gun mount. Placing badly burned Machinists Mate 1/c Patrick MacMahon and two non-swimmers aboard the float, the survivors succeeded in evading Japanese patrols and landed on uninhabited Plum Pudding Island. Over the next two nights, Kennedy and Ensign George Ross unsuccessfully attempted to signal patrolling PT boats with a salvaged battle lantern. With their provisions exhausted, Kennedy moved the survivors to nearby Olasana Island which possessed coconuts and water. Seeking additional food, Kennedy and Ross swam to Cross Island where they found some food and a small canoe. Using the canoe, Kennedy came into contact with two local islanders but was unable to get their attention. These proved to be Biuku Gasa and Eroni Kumana, who had been dispatched by Sub Lieutenant Arthur Reginald Evans, an Australian coastwatcher on Kolombangara, who had seen PT-109 explode after the collision with Amagiri. On the night of August 5, Kennedy took the canoe into the Ferguson Passage to try to contact a passing PT boat. Unsuccessful, he returned to find Gasa and Kumana meeting with the survivors. After convincing the two men that they were friendly, Kennedy gave them two messages, one written on a coconut husk, to take to the coastwatchers at Wana Wana. The next day, eight islanders returned with instructions to take Kennedy to Wana Wana. After leaving supplies for the survivors, they transported Kennedy to Wana Wana where he made contact with PT-157 in the Ferguson Passage. Returning to Olasana that evening, Kennedys crew was ferried to the PT boat and transported to Rendova. For his efforts to rescue his men, Kennedy was awarded the Navy and Marine Corps Medal. With Kennedys political ascent after the war, the story of PT-109 became well known and was the subject of a feature film in 1963. When asked how he became a war hero, Kennedy replied, It was involuntary. They sank my boat. The wreck of PT-109 was discovered in May 2002 by noted underwater archaeologist and oceanographer Dr. Robert Ballard.