Scott Cumston 5/15/2013 NGT1310 Wednesday 165 Physical Networking Instructor: Robert Freid Physical Networking Unit 9 Assignments Unit 9 Exercise 1 – Definitions for Light Sources and Components 1. Forward Biased LED - When an LED is forward biased, the anode is connected to positive and cathode is connected to negative terminal of the supply, then current flows through the LED, just like in a regular diode. 2. Incoherent Light – Light in which the electric and magnetic fields of photons are completely random in orientation. 3. Laser – An acronym for light amplification by stimulated emission of radiation. The laser produces a coherent source of light with a narrow beam and a narrow spectral bandwidth (about 2cm). Lasers in fiber optics are usually solid-state semiconductor types. Used to provide the high-powered, tightly controlled light wavelengths necessary for high-speed, long-distance optical fiber transmissions. 4. Output Pattern – The LED and laser semiconductors used in fiber-optic light sources are packaged to couple as much light as possible into the core of the optical fiber. The LED has a wide output pattern compared to a laser and does not couple all its light energy into the core of a multimode optical fiber. The output pattern of a laser light source is very narrow, allowing a majority of the light energy to be coupled into the core of a single-mode or multimode optical fiber. 5. Output Power – Amount of power a component, circuit or system can deliver to a load. 6. Modulation Speed – The modulation speed of a light source is just one factor that can limit the performance of a fiber-optic communication system.
7. Core Diameter Mismatch – This occurs when the core diameter of the transmitting fiber (t) is larger than the core diameter of the fiber at the receiving end (r). 8.
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