电子英语证书考试电子英语证书考试(PEC)-光电子学术语光电子学术语A ABSORPTION - Losses in an optical fiber caused by the presence of some impurities - iron, copper, cobalt, vanadium, and chromium. For optical fibers, even one or two parts per billion of these impurities are considered unacceptable. ACCEPTANCE PATTERN - Curve of total transmitted light plotted against the incident angle ALPHANUMERIC DISPLAY - Readout of numbers and letters ANALOG DISPLAY - Readout that provides a continuous, illuminated movement along a predetermined calibrated path to provide an indication of a desired measurement ANALOG METER - Readout that provides a continuous numbered scale along which a pointer moves C CLADDING - A thin glass or plastic material applied to the surface of a fiber optic strand core, having less density than the core. If a light strikes the boundary between the two materials at a suitable angle, the light is reflected back into the denser core. CONNECTOR INSERTION LOSS - Light loss, expressed in decibels (dB), caused by the insertion of a mating connector between two sections of a fiber optic transmission system CONTRAST - The difference in light output between the areas of a display that are illuminated and non-illuminated CORE - The inner section of a fiber optic strand made of either pure glass (silica) or plastic through which light is guided. Typically, it is approximately .01 to .05 inches in diameter. CURRENT TRANSFER RATIO (CTR) - Ratio of an opto-couplers output current to its input current DDARK CURRENT - The output current of a photodetector with no light at its input. DECODER/DRIVER - A circuit that converts digital information into analog voltages, then amplifies the voltages to an adequate level to energize the elements of a display DIGITAL DISPLAY - A readout of alphanumerics (letters and numbers) as opposed to analog or linear meter indications DOMINANT WAVELENGTH - The wavelength that is a quantitative measure of the color of light as perceived by the human eye. DOT-MATRIX DISPLAY - A formation of dots arranged in an array of rows and columns, capable of being individually illuminated to produce alphanumeric characters and graphics DYNAMIC SCATTERING LCD - One technique that causes ambient light to be scattered when the LCD segments are properly energized, producing a readout E ELECTROLUMINESCENT (EL) DISPLAY - A display of segments or dots of transparent conductive electrodes separated by a thin dielectric containing a luminescent phosphor. Application of AC voltage across opposing electrodes will cause the dielectric to glow with a characteristic bluish-green light. EMITTER - The light source in a fiber optic system F FIBER OPTICS - The technology of transmitting and guiding optical radiation (light) along optical conductors FIBER OPTIC CABLE - A bundle of optical fibers within one conducting cable. In addition to the optical fibers and its cladding, the cable can consist of plastic strength members, an inner and an outer plastic jacket, all providing protection to the fiber strands. FIBER OPTIC CONNECTOR - A quick connect/disconnect assembly to interconnect: a light source to a fiber optic cable; a fiber optic cable to another fiber optic cable; a fiber optic cable to a light detector FIBER OPTIC COUPLER - A mechanical component that interconnects a number of fiber optic cables in a bidirectional system by mixing and splitting all light signals within the cable FIBER OPTIC SPLICE - A non-separable junction joining two fiber optic cables. The connection is made with the use of an epoxy adhesive or by thermal bonding. FLUORESCENT DISPLAY - A vacuum tube display with a phosphor-coated screen that glows with a characteristic bluish-green light when bombarded with electrons from a heated filament. G GALLIUM ARSENIDE (GaAs) - A compound of gallium and arsenic used to produce LEDs GALLIUM ARSENIDE PHOSPHIDE (GaAsP) - A compound of gallium, arsenic, and phosphorus used to produce LEDs GALLIUM PHOSPHIDE (GaP) - A compound of gallium and phosphorus used to produce LEDs GAS DISCHARGE DISPLAY - A display in which patterned segments or dots, containing an inert gas, are under the surface of a glass screen. The display is illuminated by the application of a sufficiently high voltage to ionize the gas and emit a light on the screen. The light is generally characterized by a bluish-green color. Also called a PLANAR or PLASMA display. GRADED INDEX FIBER - An optical fiber whose gradually changing density provides high density at its center and low density at the core-cladding interface. Instead of reflected light sharply zig-zagging, the reflected light in the fiber travels in a smooth, curving path, and reducing distortion in the fiber. GROUND LOOP NOISE - An undesirable voltage generated in the common reference of a relatively low-level signal circuit by magnetic fields or by the return or reference currents produced by relatively high-power circuits connected to the sa