1、电子英语证书考试(PEC)-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 transmitt
2、ed 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 c
3、ontinuous 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 t
4、he 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
5、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
6、 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)
7、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 pr
8、oduce 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 separat
9、ed 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 o
10、ptical 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 f
11、iber 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 fibe
12、r 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 displa
13、y 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 phosph
14、orus 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 su
15、fficiently 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 a
16、t 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 circu
17、it by magnetic fields or by the return or reference currents produced by relatively high-power circuits connected to the same circuit reference (ground). This is a potentially detrimental condition, generally caused by poor circuit layout of a PC board. I ILLUMINATED LEGEND DISPLAY - A display in wh
18、ich information is imprinted on a translucent surface and illuminated by backlighting INFRARED RADIATION - Radiation in the electromagnetic wavelength region situated between 750 and 1000 nanometers IONIZATION - The breakdown of an inert gas when a high voltage of sufficient amplitude is applied acr
19、oss the terminals (electrodes) of the component IRED - An infrared emitting diode. See LIGHT EMITTING DIODE L LEAST SIGNIFICANT DIGIT - The numeral at the right-hand position of a digital numerical display LED ARRAY - A number of independent LED chips in a package LIGHT CURRENT - The current flowing
20、 through a photodetector when light is applied to its input. Also called PHOTO CURRENT LIGHT EMITTING DIODE (LED) - A semiconductor diode that emits monochromatic (single color) light when forward biased. The emitted light can be red, yellow, orange, green, blue, or nonvisible infrared. LIGHT DETECT
21、OR - A component that converts optical energy (light) into electricity. See PHOTODETECTOR LIGHT REPEATER - An electronic circuit that converts a light signal to an electrical signal, amplifies the electrical signal and then changes the electrical signal back to an amplified version of the original l
22、ight signal. Essentially, it is a light amplifying circuit when applied to a fiber optic system. LINEAR READING - An equal change in visual indication for a given change in the quantity being measured. The term LINEAR is often interchanged with the term ANALOG. LIQUID CRYSTAL DISPLAY (LCD) - A displ
23、ay having conductive segments or dots deposited on the inside surfaces of two transparent glass plates separated by a crystal in liquid form. When energized with AC voltage in the presence of light, the selected segments will provide a black-tone or gray readout. LUMINANCE CONTRAST - The observed br
24、ightness of a light emitting diode display element compared with the brightness of the surrounding field that is an integral part of the device M MONO-MODE FIBER - A fiber optic type where the diameter of the core is slightly larger than the wavelength of the transmitted light. All light beams trave
25、l in a straight path through the fiber, providing a greatly increased information-carrying capacity with a minimum of distortion when compared with the step-index and graded-index fibers. MOST SIGNIFICANT DIGIT - The numeral at the left-hand position of a digital numerical display MULTIPLEXING - A d
26、isplay drive technique used with multiple-digit (four or more) displays. Selected digits are pulsed at a high peak current and low duty cycle so that the human eye can not discern when the digits are being turned OFF. As a result, the total display power is reduced. Since some of the drive circuitry
27、 is shared by all the display digits, fewer parts are used. Also called STROBING N NEMATIC LIQUID - The display medium in a liquid crystal display. A nematic liquid is characterized by having its crystalline structure, or lattice, totally aligned when no energizing voltage is applied, resulting in a
28、 transparent liquid. See LIQUID-CRYSTAL DISPLAY. NUMERICAL APERTURE (NA) - The characteristic of a fiber optic strand which defines its acceptance of impinging light. The degree of openness, light gathering ability, and angular acceptance are other terms describing this characteristic. O OPTO-COUPLE
29、R (OPTO-ISOLATOR) - A component capable of optically transferring an electrical signal between two circuits and, at the same time, electrically isolating these circuits from each other. It consists of an infrared LED emitting, section at its input, and a silicon photodetector, at its output, with ot
30、her circuitry sometimes included as part of the device. OPTOELECTRONICS - The technology that merges the sciences of electronics and optics P PEAK WAVELENGTH - The wavelength at the peak of the radiated spectrum of a light emitter PHOTO DARLINGTON - A pair of bipolar transistors connected in a Darli
31、ngton configuration to provide very high current gain and often used as the photodetector section of an opto-coupler PHOTODETECTOR - A device capable of sensing light and converting it to electricity PHOTO DIODE - A silicon diode used as a photodetector PHOTO SCR - A silicon controlled rectifier tha
32、t acts as the photodetector section of an opto-coupler PHOTO TRANSISTOR - A bipolar transistor used as a photodetector. It provides current at its output that is proportional to light intensity at its input. The low-level input light current is amplified by the current gain (beta) of the transistor.
33、 PLANAR DISPLAY or PLASMA DISPLAY - See GAS DISCHARGE DISPLAY POINT SOURCE - A light source with a maximum dimension less than one-tenth the distance between source and detector POLARIZER or POLARIZED FILTER - A transparent film that allows light to pass through it in one plane and blocks light in o
34、ther planes S SCATTERING - A change in the light wave passing through an optical fiber caused by an impurity or change of density in the fiber. This effect produces losses in the fiber. SEGMENTED DISPLAY - A pattern of a specific number of segments arranged in a rectangular form to provide an alphan
35、umeric display when energized. SPLICE - A non-separable junction joining two fiber optic conductors. A splice can be accomplished either by fusing the two optical conductors with heat or by using an epoxy adhesive. STEP-INDEX FIBER - The simplest form of optical fiber that is based on the principle
36、of total internal reflection within the fiber strand or rod. When a light beam is applied at one end, the light will bounce through the fiber in a zig-zag manner and emerge at the other end with the emerging angle equal to the incident angle. STROBING - See MULTIPLEXING SUPERTWISTED BI-FRINGENCE EFF
37、ECT (SBE) - An advanced approach to liquid crystal displays which offers a distinct improvement in contrast (particularly in ambient low-level light) over the older nematic field-effect LCD T THIN-FILM ELECTROLUMINESCENCE (TFEL) - An advanced approach to the production of large-panel fluorescent displays that allows them to compete with other display technologies in data-display and graphics-display applications V VAPOR DEPOSITION - A processing step in the manufacture of optical glass fiber to reduce the inherent metallic impurities in the material, thereby minimizing light distortion
