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Mahmoud Al-Saba – 223132 Majed Al-Bishi – 216423 1 History of Fiber Optic Technology People have used light to transmit info. for hundreds of years The invention of the laser prompted researchers to study the potential of fiber optics send a much larger amount of data than telephone first experiment letting the laser beam transmit freely in air & through different types of waveguides very large losses in the optical fibers prevented coaxial cables from being replaced Decrease in the amount of light reaching the end of the fiber Cont: History of Fiber Optic Technology Early fibers had losses around 1,000 dB/km In 1969, several scientists concluded that impurities in the fiber material caused the signal loss Researchers believed it was possible to reduce the losses By removing the impurities researchersobserve the improvement In 1970,(corning glass works)* made a multimode fiber with losses under 20 dB/km. in 1972, the company made a high silica-core multimode optical fiber with 4dB/km. Nowadays, multimode fibers can have losses as low as 0.5 dB/km at wavelengths around 1300 nm *company Introduction Optical fiber has a number of advantages over the copper wire since it is made glass or plastic light has a much higher frequency than any radio signal we can generate, fiber has a wider bandwidth To carry more information at one time Transmitters transmitters include an LED(Light-emitting diodes) or laser diode LED produce incoherent light have relatively large emitting areas and as a result are not as good light source they are widely used for short distances because they are much more economical Cont: Transmitters Laser diode produce coherent light used for applications that require the transmission of signals over long distances Important performance specifications data rate transmitter rise time wavelength spectral width maximum optical output power Receivers Receivers are instruments that convert light into electrical signals. component of an optical receiver is a photo detector that converts light into electricity use three types of photodiodes positive-negative (PN) junctions positive-intrinsic-negative (PIN) photodiodes avalanche photodiodes (APD) Optical Fiber Fiber is the medium to guide the light form the transmitter to the receiver. There are two types: Multimode Fiber Single-Mode Fiber Multimode Fiber In multimode fibers more than one light transmitted at a time. Fiber diameter ranges from 50-to-100 micron. 9 Multimode Fiber Multimode Fiber is divided into two types: Multimode Step-index Fiber Multimode Graded-index Fiber Multimode Step-index Fiber Lights are sent at angles lower than the critical angle or straight Any light angle exceed the critical angle will cause it to penetrate through cladding. Obviously light with lower angle will reach the end faster than others. Multimode Step-index Fiber The difference in signals receiving time result in unstable wave light at the receiver. To avoid this problem there should be spacing between the light pulses but this will limit the bandwidth. Used for very short distance Multimode Graded-index Fiber In this mode reduce the problem with Multimode Step-Index. All the beams reaching the receiver almost at the same time. This can be done by slowing down the ones with shorter distance. This is done in fiber implementation by increasing its refractive index at the center and gradually decreases it toward the edges Single-Mode Fiber Only one light is transmitted in the fiber. Diameter ranges from 8.3 to 10 microns. It has Higher transmission rate. it can be used for longer distance. Fiber Cables Advantages of Cabling fiber: Ease of Handling Protection Crush Resistance Degradation Types of Fiber Cables: Loose Tube Cable Tightly Buffered Cable Ribbon Cables Wave Division Multiplexing (WDM) it is a way to send multiple optical signals from deferent source at the same time on one optical fiber. Used with single mode fiber How it works: At the sender the data stream from each Source is assigned an optical wavelength. The multiplexer modulates each data stream from each Source. The resulted optical signal generated for each source data stream is placed on its assigned wavelength. Wave Division Multiplexing (WDM) The resulted signals are simultaneously sent through the fiber. At the receiver the signal is separated into the original signals according to their different wavelengths by using prisms. These signals are further demodulated. Then, The resulting separated data streams are provided to the respective Users. Some Application Long telecommunication systems on land and at sea to carry many simultaneous telephone calls (or other signals) over long distances. Links among computers and high resolution videoterminals. Local area Networks operating at high speeds. Connections between the telephone N/W and antennas for mobile telephone service. Interoffice trunks that carry many telephone conversations simultaneously between local and regional switching facilities. Thank you Any Question please 19