| s: Abbreviation for
second. |
| Sampling
Rate: The number of discrete sample measurements made in a given
period of time. Often expressed in megahertz (MHz) for video. |
| SAP (Secondary Audio
Programming): Secondary audio signal that is broadcast along with a
television signal and its primary audio. SAP may be enabled through either
the television, stereo VCR equipped to receive SAP signals, or an SAP
receiver. SAPs may be used for a variety of enhanced programming,
including providing a "video description" of a program's key visual
elements, inserted in natural pauses, that describes actions not otherwise
reflected in the dialog, used by visually impaired viewers. This service
also allows television stations to broadcast programs in a language other
than English, and may be used to receiver weather information, or other
forms of "real-time" information. |
| SAN (Storage Area Network): Connects a group
of computers to high-capacity storage devices. May be incorporated into local
area networks (LAN), metropolitan
area networks (MAN), and wide
area networks (WAN). |
 |
| Saturation: 1) In a communications
system, the condition in which a component of the system has reached its
maximum traffic handling capacity. 2) The point at which the output of a linear
device, such as a linear amplifier, deviates significantly from being
a linear function of the input when the input signal is increased. 3) The
degree of the chroma or purity of a color. |
| S-Band: The
wavelength region between 1485 nm and 1520 nm used in some CWDM and DWDM applications. |
| SBS: See stimulated
Brillouin scattering. |
| SC: Abbreviation
for subscription channel connector. A push-pull type of optical connector that features high packing density, low loss, low backreflection,
and low cost. |
 |
| Scattering: The
change of direction of light rays or photons after striking small
particles. It may also be regarded as the diffusion of a light beam caused by the inhomogeneity of the transmitting material. |
 |
| Scalable Coding: The ability to
encode a visual sequence so as to enable the decoding of the digital data
stream at various spatial and/or temporal resolutions. |
| Scalable Video: Refers to video
compression that can handle a range of bandwidths,
scaling smoothly over them. |
| Scanning: 1) In telecommunications
systems, periodic examination of traffic activity to determine whether
further processing is required. 2) In television, facsimile, and picture
transmission, the process of successively analyzing the colors and
densities of the object according to a predetermined pattern. |
| S-CDMA: Abbreviation for synchronous code division multiple
access. A synchronized version of CDMA. |
 |
| SCM: Abbreviation for subcarrier multiplexing.
The process by which multiple subcarrier signals are combined onto one
signal. |
| Scrambler: 1) A
device that transposes or inverts signals or otherwise encodes a message
at the transmitter to make the message unintelligible at a receiver not equipped with an appropriately set descrambling device.
Scramblers usually use a fixed algorithm or mechanism. 2) A device
intended to normalize the duty cycle of a data stream to be close to
50%. |
| Scrambling: To transpose or invert digital data according to a prearranged scheme in order to break up the
low-frequency patterns associated with serial digital signals. |
| SCSI: Acronym for
small computer system interface. An intelligent interface device that
expands a microprocessor (CPU) bus to facilitate connections to multiple
peripherals (e.g., CD-ROM drives, hard drives, or scanners) and exchange
data with those peripherals via a separate communications bus. |
| SDTV: Abbreviation
for standard-definition television. Synonym NTSC television transmission. |
| SECAM: Abbreviation
for Système Électronique Couleur avec Mèmoire. A TV
standard used in various parts of the world. Delivers 625 lines at 50
frames per second. |
| Selfoc
Lens: A trade name used by the Nippon Sheet
Glass Company for a graded-index
fiber lens; a segment of graded-index fiber made to serve as a
lens. |
| Self-phase modulation (SPM): A
fiber nonlinearity caused by the nonlinear index
of refraction of glass. The index of refraction varies with optical
power level causing a frequency chirp which interacts with the fiber’s dispersion to broaden the pulse. |
 |
| Semiconductor Optical Amplifier
(SOA): A laser
diode without end mirrors coupled to the fibers on both ends. Light coming in either fiber is amplified by a single pass
through the laser diode. An alternative to EDFAs. |
 |
| Sensitivity: See receiver
sensitivity. |
| Serial: One bit at
a time, along a single transmission path. |
| Serial
Digital: Digital information that is transmitted in serial form.
Often used informally to refer to serial digital television
signals. |
| Serial Digital Interface
(SDI): A 10-bit, scrambled, polarity independent interface, based
on a 270 Mb/s data rate, with common scrambling for both component ITU-R 601, composite digital video, and four channels
of (embedded) digital audio. Most new broadcast digital equipment includes
SDI. |
| Serial Digital Transport
Interface (SDTI): Another name for SMPTE 305M.
Allows faster-than-real-time transfers between various servers and between
acquisition tapes, disk-based editing systems and servers. Supports both
270 Mb/s and 360 Mb/s data rates. |
| Servo-loop: Automatic
device for regulating |
| Set-top Box: See STB. |
| SH: Abbreviation for
short-haul. A classification of video performance under RS-250B/C. Higher
performance than long-haul or medium-haul. |
| Sheath: An
outer protective layer of a fiber optic cable.
Also called the cable jacket. |
 |
| Shot Noise: Noise caused by current fluctuations arising from the discrete
nature of electrons. |
| Si: Abbreviation for silicon. Generally used in detectors. Good for
short wavelengths only (e.g., < 1000 nm). |
| Sideband: Frequencies
distributed above and below the carrier that contain energy resulting from amplitude
modulation. The frequencies above the carrier are called upper
sidebands, and the frequencies below the carrier are called lower
sidebands. |
| Silica
Glass: Glass made mostly of silicon dioxide, SiO2,
used in conventional optical
fibers. |
| Signal-to-Noise Ratio (SNR): The
ratio of the total signal to the total noise which shows how much higher
the signal level is than the level of the noise. A measure of signal
quality. |
| Simple Network
Management Protocol (SNMP): The Internet standard protocol for network management software. It monitors devices on
the network, and gathers device performance data for management
information data bases (MIB). |
| Simplex: Single element
(e.g., a simplex connector is a single-fiber connector). |
| Simplex
Cable: A term sometimes used for a single-fiber cable. |
| Simplex Transmission: Transmission in one direction only. Also referred to as half-duplex
transmission. |
 |
| Single Attachment Concentrator: A concentrator that offers one attachment to the FDDI network. |
| Single-line Laser: See single-longitudinal
mode laser. |
| Single-longitudinal
Mode Laser (SLM): An injection laser
diode which has a single dominant longitudinal mode. A single-mode
laser with a side mode suppression ratio (SMSR)< 25 dB. |
 |
| Single-mode (SM) Fiber: A small-core optical
fiber through which only one mode will propagate. The typical diameter is 8-9 microns. |
 |
| Single-mode Laser Diode (SMLD): See single-longitudinal
mode laser. |
| Single-mode Optical Loss Test
Set (SMOLTS): An optical
loss test set for use with single-mode fiber. |
| SI Units: Abbreviation for Système Internationale (in English,
International System of Units), commonly known as the metric
system. |
| SLED: See surface-emitting
diode. |
| SLM: See single-longitudinal
mode laser. |
| Slope
Efficiency (SE): This is the mean value of the incremental change
in optical power for an incremental change in forward current when the
device is operating in the lasing region of the optical power output
versus forward current curve. Also referred to as differential
efficiency. |
| SMF: Abbreviation for single-mode
fiber. |
| SMA: A threaded
type of optical connector.
One of the earliest optical connectors to be widely used. Offers poor
repeatability and performance. |
 |
| Smart
Structures: Also smart skins. Materials containing sensors
(fiber optic or other types) to measure their properties during
fabrication and use. |
| SMD: Abbreviation for
surface-mount device. See SMT. |
| SMPTE: Abbreviation for Society of Motion Picture and Television
Engineers. Organization that publishes ANSI-approved standards,
recommended practices, and engineering guidelines for the motion picture
and television industry. |
http://www.smpte.org |
| SMPTE 259M:
Television standard, written by the Society of Motion Picture and
Television Engineers (SMPTE), that
describes a serial digital interface (SDI) for 10-bit 4:2:2 component and 4fsc composite digital transport. |
| SMPTE 310M:
Television standard, written by the Society of Motion Picture and
Television Engineers (SMPTE), that
describes a synchronous serial interface for MPEG-2 digital transport streams. |
| SMT: Abbreviation
for surface-mount technology. An electronics
manufacturing technique. |
| S/N: See signal-to-noise
ratio. |
| SNR: See signal-to-noise
ratio. |
| SOA: See semiconductor
optical amplifier. |
| Soliton
Pulse: An optical pulse having a shape,
spectral content, and power level designed to take advantage of nonlinear
effects in an optical fiber waveguide,
for the purpose of essentially negating dispersion over long distances. |
| SONET: Abbreviation for
synchronous optical network transport system. An interface standard widely
used by the telecom industry where OC-3 is the lowest current rate (155.5
Mb/s), and OC-768 is the highest rate being contemplated (39.808 Gb/s).
Valid rates increase by a factor of four from the OC-3 rate up to
OC-768. |
Source: In fiber optics,
a transmitting LED or laser
diode, or an instrument that injects test signals into fibers. |
| Span
Engineering: The process of designing a DWDM transmission span to achieve the required performance based on fiber type,
the transmission distance, amplifier spacing, noise, power, and channel
count. |
| Spectral
Efficiency: The number of data bits per second that can be
transmitted in a one Hertz bandwidth range. |
| Spectral Width: A
measure of the extent of a spectrum. For a source, the
width of wavelengths contained in the output at one half of the wavelength of peak power.
Typical spectral widths are 50 to 160 nm for an LED and less than 5 nm for a laser
diode. |
 |
| Spectral Width, Full
Width, Half Maximum (FWHM): The absolute difference between
the wavelengths at which the spectral radiant intensity is 50 percent of the maximum
power. |
| Splice: A
permanent connection of two optical
fibers through fusion or mechanical means. |
 |
| Splitter: see Coupler. |
| Splitting
Ratio: The ratio of power emerging from two output ports of a coupler. |
| SPM: See self-phase
modulation. |
| SRS: See stimulated Raman
scattering. |
| ST: Abbreviation
for straight tip connector.
Popular fiber optic connector originally developed by AT&T. |
 |
| Stabilized Light Source: An LED or laser
diode that emits light with a controlled and constant spectral
width, center
wavelength, and peak
power with respect to time and temperature. |
| Star Coupler: A coupler in which power at any input port is distributed to all output
ports. |
 |
| Star
Network: A network in which all terminals are connected through a single point, such as a star
coupler or concentrator. |
| STB: Abbreviation for
set-top box. An auxiliary device that usually sits on top of or adjacent
to a television receiver used in direct analog or digital satellite
transmission and digital television to view the signals on an analog TV.
Converter boxes are becoming obsolete as old model televisions requiring a
converter are replaced by modern televisions, which incorporate a
converter into the television. Also called a set-top converter. |
| Step-index Fiber: Fiber that has a uniform index
of refraction throughout the core that is a step below the index of refraction in the cladding. |
 |
| Stimulated Brillouin Scattering
(SBS): The easiest fiber nonlinearity to trigger. When a powerful light wave travels through a fiber it interacts with acoustical vibration modes in the glass. This causes a scattering mechanism to be formed that reflects much of the light back to the source. |
 |
| Stimulated Raman Scattering (SRS): A fiber nonlinearity similar to SBS but having a much higher threshold. This mechanism can also
cause power to be robbed from shorter wavelength signals and provide gain
to longer wavelength signals. |
 |
| Strength
Member: The part of a fiber
optic cable composed of aramid yarn, steel strands, or fiberglass
filaments that increase the tensile strength of the cable. |
| Submarine Cable: A
cable designed to be laid underwater. |
 |
| Subscriber
Loop: Also called local loop.
The link from the telephone company central
office (CO) to the home or business (customer premises). |
| Sun
Fade: In satellite systems, the loss of a satellite signal that
occurs when energy from the sun overpowers the satellite's signal. Also
called sun transit or sun outage. |
| Supertrunk: A cable that carries several video channels between facilities of a cable
television company. |
| Surface-emitting Diode: A simple and inexpensive LED that emits light from its flat surface rather than its side with emission
spread over a wide angle. |
 |
| Surround Sound: More commonly referred to as
Dolby Digital, a standard for high-quality digital audio that is used for
the sound portion of video stored in digital format, especially videos stored on DVD-ROMs. Dolby Digital delivers 6
channels in the so called "5:1" configuration: left, right, and center
screen channels, separate left and right sounds, and a subwoofer channel. |
| Switch: 1) In
communications systems, a mechanical, electro-mechanical, or electronic
device for making, breaking, or changing the connections in or among
circuits. 2) Synonym for central office, switching center. 3) In
communications systems, to transfer a connection from one circuit to
another. |
| Synchronization Pulse: 1) A signal
derived from the composite or combination of the horizontal and vertical
drives. 2) A pulse used to achieve or maintain synchronism, usually
applied to analog signals. (The term "synchronization bit" is usually
applied to digital data streams.) Commonly called the sync pulse. See also composite
sync. |
| Synchronous: A data signal that is sent along with a clock signal. A system in
which events, such as signals, occur at evenly spaced time durations.
Opposite of asynchronous. |
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