| 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
is even or odd. If the number of 1's is even,
the parity is said to be even; if the number
of 1's is odd, the parity is said to be odd. |
 |
| 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
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. |
 |
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. |
 |
| 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. |
 |
| 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. |
 |
| 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-Multipoint
Transmission: |
|
| Point-to-Point Transmission: Transmission
between two designated stations. |
|
| 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 Maintaining
Fiber: Fiber designed to
propagate only one polarization of light that
enters it. |
|
| 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. |
Click
on the image 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 CO, or a CATV headend and the subscriber’s
home. |
 |
| 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 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. |
 |
| 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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