Montie Ramsarran August 11th, 2014 NT1310 Mr. Amos

Unit 9 Exercise 1 Light Source and Components-Definitions

1. Forward Biased LED: A bias voltage that is applied to a pn-junction in the direction that causes a large current flow; used in some semiconductor diode circuits. 2. Incoherent Light: Light in which the electric and magnetic fields of photons are completely random in orientation. Incoherent light is typically emitted from light bulbs and LEDs. 3. Laser: 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. Lasers are used to provide the high-powered, tightly controlled light wave lengths necessary for high-speed, long-distance optical fiber transmissions. 4. Output Pattern: A setting that selects the output pattern for comparison outputs. This enables outputs for changes in levels rather than just upper/lower limit comparisons to set value. It can be set according to the control applications. Note: The settings must be as follows for correct zone outputs. 5. Output Power: The useful signal or power delivered by a circuit or device. 6. Modulation Speed: (1) Coding of information onto the carrier frequency. Types of modulation include amplitude modulation (AM), frequency modulation (FM), and phase modulation (PM). (2) When light is emitted by a medium, it is coherent, meaning that it is in a fixed-phase relationship within fixed points of the light wave. The light is used because it is a continuous, or sinusoidal, wave (a white or blank form) upon which a signal can be super imposed by modulation of that form. The modulation is a variation imposed upon this white form, a variation of amplitude, frequency, or phase of the light. There are two basic forms of this modulation: one by an analog form, another by a digital signal. This signal is created in the form of the “intelligence” and superimposed upon the light wave. It is then demodulation by a photo detector and converted into electrical energy. 7. Core Diameter Mismatch: The central part of a single optical fiber in which the light signal is transmitted. Common core sizes are 8.3 microns, 50 microns, and 62.5 microns. The core is surrounded by a cladding that has a higher refractive index that keeps the light inside the core. The core is typically made of glass or plastic. 8. Current: The flow of electrons in a conductor alternating current and direct current. 9. PIN Photodiode: is a diode with a wide, lightly doped 'near' intrinsic semiconductor region between a p-type semiconductor and an n-type semiconductor region. The p-type and n-type regions are typically heavily doped because they are used for ohmic contacts. 10. Avalanche Photodiode: With respect to optical fiber equipment, a specialized diode designed to use the avalanche multiplication of photocurrent. The photodiode multiplies the effect of the photons it absorbs, acting as an amplifier. 11. Responsivity: (1) The ratio of a detector’s output to input, usually measured in units of amperes per watt (or microamperes per microwatt). The measure of how well a photodiode converts a wavelength or range of wavelengths of optical energy into electrical current. 12. Optical Subassembly: The portion of a fiber-optic receiver that guides light from the optical fiber to the photodiode. 13. Dynamic Range: The difference between the maximum and minimum optical input power that an optical receiver can accept. 14. Operating Wavelength: The wavelength at which a fiber-optic receiver is designed to operate. Typically, an operating wavelength includes a range of wavelengths above and below the stated wavelength. 15. Fiber-Optic Coupler: is a device used in optical fiber systems with one or more input fibers and one or several output fibers. Light entering an input fiber can appear at one or more outputs and its power distribution potentially depending on the wavelength and polarization. 16. Optomechanical Switch: produces different optical paths from two optical path sections out of a plurality of optical path sections that are oriented in different spatial directions. 17. Optical Attenuator: Reduces the intensity of light waves, usually so that the power is within the capacity of the detector. There are three basic forms of attenuators: fixed optical attenuators, stepwise variable optical attenuators, and continuous variable optical attenuators. Attenuation is normally achieved either by a doped fiber or an offset or core misalignment. 18. Optical Isolator: A component used to block out reflected and other unwanted light. 19. Wavelength Division Multiplexing: A method of carrying multiple channels through a fiber at the same time (multiplexing) whereby signals within a small spectral range are transmitted at different wavelengths through the same optical-fiber cable. 20. Passive Optical Network: is a telecommunications network that uses point-to-multipoint fiber to the premises in which unpowered optical splitters are used to enable a single optical fiber to serve multiple premises. 21. FTTH (fiber-to-the-home): Fiber reaches the boundary of the living space, such as a box on the outside wall of a home. Passive optical networks and point-to-point Ethernet are architectures that deliver triple-play services over FTTH networks directly from an operator's central office. 22. FTTB (fiber-to-the-building, -business, or -basement): Fiber reaches the boundary of the building, such as the basement in a multi-dwelling unit, with the final connection to the individual living space being made via alternative means, similar to the curb or pole technologies. 23. FTTC (fiber to closet, or –cabinet) very similar to FTTN, but the street cabinet or pole is closer to the user's premises, typically within 1,000 feet (300 m), within range for high-bandwidth copper technologies such as wired Ethernet or IEEE 1901 power line networking and wireless Wi-Fi technology. FTTC is occasionally ambiguously called FTTP (fiber-to-the-pole), leading to confusion with the distinct fiber-to-the-premises system. 24. FTTN (fiber-to-the-node): Fiber is terminated in a street cabinet, possibly miles away from the customer premises, with the final connections being copper. FTTN is often an interim step toward full FTTH and is typically used to deliver advanced triple-play telecommunications services. 25. Feeder Cable: A voice backbone cable that runs from the equipment room cross-connect to the telecommunications cross-connect. A feeder cable may also be the cable running from a central office to a remote terminal, hub, head end, or node. 26. Distribution Cable: An optical fiber cable used “behind-the-shelf” of optical fiber patch panels; typically composed of 900 micron tight buffered optical fibers supported by aramid and/or glass-reinforced plastic (GRP). 27. Drop Point: A single length of cable installed between two points. 28. Local Coverage Point: The distribution of broadband access then continues at the local convergence point which serves as a point of flexibility and where splitters would be located in PON systems. 29. Network Access Point: was a public network exchange facility where Internet service providers (ISPs) connected with one another in peering arrangements. 30. Network Interface Device: is a device that serves as the demarcation point between the carrier's local loop and the customer's premises wiring.