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Alphabet A Through Z

A B C D E F G H I J K L M #
N O P Q R S T U V W X Y Z
P
p: Abbreviation for pico. One trillionth or 10-12.
pA: Abbreviation for picoamp. One trillionth of an Amp or 10-12 Amps.
PABX: Abbreviation for private automatic branch exchange. See PBX.

Packet: In data communications, a sequence of binary digits, including data and control signals, that is transmitted and switched as a composite whole. The packet contains data, control signals, and possibly error control information, arranged in a specific format.

Packet Switching: The process of routing and transferring data by means of addressed packets so that a channel is occupied during the transmission of the packet only, and upon completion of the transmission the channel is made available for the transfer of other traffic.

PAL: Abbreviation for phase alternation by line. A composite color standard used in many parts of the world for TV broadcast. The phase alternation makes the signal relatively immune to certain distortions (compared to NTSC). Delivers 625 lines at 50 frames per second. PAL-plus is an enhanced-definition version.
Parity: A term used in binary communication systems to indicate whether a number of 1’s in a transmission plus a parity bit is even or odd. If the total number of 1’s is even, the parity is said to be even; if the total number of 1’s is odd, the parity is said to be odd. Even Parity
Passband: The region of usable frequency in electronics or wavelength in optics.
Passive Branching Device: A device which divides an optical input into two or more optical outputs.

Passive Branching Device

Passive Device: Any device that does not require a source of energy for its operation. Examples include electrical resistors or capacitors, diodes, optical fiber (photo), cable, wires, glass, lenses, and filters. Passive Optical Splitter

Pathological Test Code: A special test pattern used with DTV and HDTV signals to create the longest strings of zeros and ones over the serial link.  This requires the serial transport link to handle much lower frequency components than is typical in a normal data link.

Pay-Per-View (PPV): An event that has an associated viewing cost, and which may be purchased separately from any package or subscription. The ordered events could include movies, special events, such as sporting, or adult programming. The event could be purchased by either impulse PPV by using a television remote (this application requires a continuous land line phone based connection), or over the phone PPV (this application may have additional costs for processing).
PBX: Abbreviation for private branch exchange. A subscriber-owned telecommunications exchange that usually includes access to public switched networks.
PC: Abbreviation for physical contact. Refers to an optical connector that allows the fiber ends to physically touch. Used to minimize backreflection and insertion loss. Physical Contact (PC) Finish on Fiber End Face
PCB: Abbreviation for printed circuit board. Also referred to as PWB (printed writing board).
PCM: See pulse-code modulation.
PCS Fiber: See plastic clad silica.
PD: See photodiode.
Peak Power Output: The output power averaged over that cycle of an electromagnetic wave having the maximum peak value that can occur under any combination of signals transmitted.
Peak Wavelength: In optical emitters, the spectral line having the greatest output power. Also called peak emission wavelength.
PFM: Abbreviation for pulse-frequency modulation. Also referred to as square wave FM.
Phase Constant: The imaginary part of the axial propagation constant for a particular mode, usually expressed in radians per unit length. See also attenuation.
Phase Noise: Rapid, short-term, random fluctuations in the phase of a wave caused by time-domain instabilities in an oscillator.
Phase-Shift Keying (PSK): 1) In digital transmission, angle modulation in which the phase of the carrier discretely varies in relation, either to a reference phase or to the phase of the immediately preceding signal element, in accordance with data being transmitted. 2) In a communications system, the representation of characters, such as bits or quaternary digits, by a shift in the phase of an electromagnetic carrier wave with respect to a reference, by an amount corresponding to the symbol being encoded. Also called biphase modulation, phase-shift signaling.
Photoconductive: Losing an electrical charge on exposure to light.
Photodetector: An optoelectronic transducer such as a PIN photodiode (illustrated) or avalanche photodiode. In the case of the PIN diode, it is so named because it is constructed from materials layered by their positive, intrinsic, and negative electron regions. PIN Photodiode
Photodiode (PD): A semiconductor device that converts light to electrical current.
Photon: A quantum of electromagnetic energy. A particle of light.
Photonic: A term coined for devices that work using photons, analogous to the electronic for devices working with electrons.
Photovoltaic: Providing an electric current under the influence of light or similar radiation.
Pigtail: A short optical fiber permanently attached to a source, detector, or other fiber optic device at one end and an optical connector at the other. Pigtail on Fiber Optic Transmitter
PIN Photodiode: See photodiode.
Planar Waveguide: A waveguide fabricated in a flat material such as thin film.
Plastic Clad Silica (PCS): Also called hard clad silica (HCS). A step-index fiber with a glass core and plastic or polymer cladding instead of glass.
Plastic Fiber: An optical fiber having a plastic core and plastic cladding.
PLC: Abbreviation for planar lightwave circuit. A device which incorporates a planar waveguide.
Plenum: The air handling space between walls, under structural floors, and above drop ceilings, which can be used to route intrabuilding cabling.
Plenum Cable: A cable whose flammability and smoke characteristics allow it to be routed in a plenum area without being enclosed in a conduit.
PMD: See polarization mode dispersion.
Point-to-Point Transmission: Transmission between two designated stations.

Point-to-Point Transmission

Polarization: The direction of the electric field in the lightwave. If the electric field  of the lightwave is in the Y Axis, the light is said to be vertically polarized. If the electric field of the lightwave is in the X axis, the light is said to be horizontally polarized. Polarization
Polarization Maintaining Fiber: Fiber designed to propagate only one polarization of light that enters it.

Cross-section of Polarization Maintaining Fiber

Polarization Mode Dispersion (PMD): Polarization mode dispersion is an inherent property of all optical media. It is caused by the difference in the propagation velocities of light in the orthogonal principal polarization states of the transmission medium. The net effect is that if an optical pulse contains both polarization components, then the different polarization components will travel at different speeds and arrive at different times, smearing the received optical signal. Polarization Mode Dispersion

(Click to Enlarge)

PON: Abbreviation for passive optical network. A broadband fiber optic access network that uses a means of sharing fiber to the home without running individual fiber optic lines from an exchange point, telco Central Office (CO), or a CATV headend and the subscriber’s home. Passive Optical Network (PON)
Port: Hardware entity at each end of the link.
POTS: Abbreviation for plain old telephone system. A call that requires nothing more than basic call handling without additional features.
p-p: Abbreviation for peak-to-peak. The algebraic difference between extreme values of a varying quantity.
PPM: Abbreviation for pulse-position modulation. A method of encoding data.
Preform: The glass rod from which optical fiber is drawn.
Profile Dispersion: Dispersion in an optical fiber attributed to the variation of refractive index contrast with wavelength.
ps: Abbreviation for picosecond. One trillionth of a second or 10-12 seconds.
PSTN: Abbreviation for public switched telephone network. A domestic telecommunications network usually accessed by telephones, key telephone systems, private branch exchange trunks, and data arrangements.
Public Switched Networks (PSN): 1. Any common carrier network that provides circuit switching among public users. 2. A switched network accessible to the public for originating and terminating telecommunications messages. 3. Any common carrier switched network, whether by wire or radio, including local exchange carriers, interexchange carriers, and mobile service providers, that use the North American Numbering Plan in common with provision of switched services.
Pulse: A current or voltage which changes abruptly from one value to another and back to the original value in a finite length of time. Used to describe one particular variation in a series of wave motions. The parts of the pulse include the rise time, fall time, and pulse width, pulse amplitude. The period of a pulse refers to the amount of time between pulses. Parts of a Pulse
Pulse-code Modulation (PCM): A technique in which an analog signal, such as a voice, is converted into a digital signal by sampling the signal's amplitude and expressing the different amplitudes as a binary number. The sampling rate must be at least twice the highest frequency in the signal.
Pulse Dispersion: The dispersion of an optical signal as it propagates through an optical fiber. Also called pulse spreading.
Pump Laser: A power source for signal amplification, typically a 980 nm or 1480 nm laser, used in EDFA applications.
Push: 1) In electronic marketing, to send data to another computer without a direct request from that computer. 2) In networking, to send data from a server to a client in compliance with a previous request from the client, as soon as the data becomes available.

pW: Abbreviation for picowatt. One trillionth of a Watt or 10-12 Watts.

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Q
QAM: See quadrature amplitude modulation.
QDST: Abbreviation for quaternary dispersion supported transmission. See DST.
QoS: See quality of service.
QPSK: See quadrature phase-shift keying.
Quadrature Amplitude Modulation (QAM): A coding technique that uses many discrete digital levels to transmit data with minimum bandwidth. 256QAM uses 16 discrete amplitude levels and 16 phase shift levels to transmit digitized video.
Quadrature Phase-shift Keying (QPSK): Phase-shift keying uses four different phase angles out of phase by 90. Also called quadriphase or quaternary phase-shift keying.
Quality of Service (QoS): 1. The performance specification of a communications channel or system which may be quantitatively indicated by channel or system performance parameters such as signal-to-noise ratio, bit error rate, message throughput rate, and call blocking probability. 2. A subjective rating of telephone communications quality in which listeners judge transmissions by qualifiers such as excellent, good, fair, poor, or unsatisfactory.
Quantization: The process of converting the voltage level of a signal into digital data before or after the signal has been sampled.

Quantizing Error: Inaccuracies in the digital representation of an analog signal. These errors occur because of limitations in the resolution of the digitizing process.

Quantizing Noise: Noise which results from the quantization process. In serial digital video, a granular type of noise that occurs only in the presence of a signal.

Quantum Efficiency: In a photodiode, the ratio of primary carriers (electron-hole pairs) created to incident photons. A quantum efficiency of 70% means seven out of ten incident photons create a carrier.
Quaternary Signal: A digital signal having four significant conditions.

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