Radio over Fiber; refers to a technology whereby light is modulated by a radio signal and transmitted over an optical fiber link to facilitate wireless access. Although radio transmission over fiber is used for multiple purposes, such as in cable television (CATV) networks and in satellite base stations, the term RoF is usually applied when this is done for wireless access. In RoF systems, wireless signals are transported in optical form between a central station and a set of base stations before being radiated through the air. Each base station is adapted to communicate over a radio link with at least one user's mobile station located within the radio range of said base station. RoF transmission systems are usually classified into two main categories (RF-over-Fiber; IF-over-Fiber) depending on the frequency range of the radio signal to be transported. [Wik1112] a) In RF-over-Fiber architecture, a data-carrying RF (Radio Frequency) signal with a high frequency (usually greater than 10 GHz) is imposed on a lightwave signal before being transported over the optical link. Therefore, wireless signals are optically distributed to base stations directly at high frequencies and converted to from optical to electrical domain at the base stations before being amplified and radiated by an antenna. As a result, no frequency up/down conversion is required at the various base station, thereby resulting in simple and rather cost-effective implementation is enabled at the base stations.
b) In IF-over-Fiber architecture, an IF (Intermediate Frequency) radio signal with a lower frequency (less than 10 GHz) is used for modulating light before being transported over the optical link. Therefore, wireless signals are transported at intermediate frequency over the optical.
A loss of vertical synchronization which causes the picture to move up or down on receiver or monitor. [Cha07] Roll-Off
A gradual attenuation of gain-frequency response at either or both ends of the transmission pass band.
Read Only Memory
RF over Glass (RFoG) Optical Network Unit; device defined by SCTE 174 2010, “Radio Frequency over Glass Fiber-to-the-Home Specification”. The RFoG system is defined to terminate at the subscriber-side interface of an RFoG Optical Network Unit (R-ONU) at the home. The specifications in SCTE 174 2010 apply to the RFoG Optical Network Unit (R-ONU) and are designed to allow interoperability between R-ONUs from various manufacturers. [SCT11] Root Private Key
The private signing key of the highest-level Certification Authority. It is normally used to sign public key certificates for lower-level Certification Authorities or other entities. Root Public Key
The public key of the highest level Certification Authority, normally used to verify digital signatures generated with the corresponding root private key.
ROSI Return On Security Investment
The portion of a connector that rotates freely, making it unnecessary to twist the entire connector (as well as any devices attached to the connector) during installation. [Arr11] Router
Routers are special network devices used to connect one recognized computer network to another. Routers work like a postal worker; they examine the To addresses of network messages they are given and use part of the address like a zip code to figure out which computer network to send it to. Once a router has figured out which network the message should go to, it sends the message to another router, which repeats the process until the last router in the chain sends it directly to the computer listed in the destination address. Most WANs use routers to connect one LAN location to another.
Routing Information Protocol (RIP)
A protocol of the Internet Engineering Task Force (IETF) for exchanging routing information about Internet Protocol (IP) networks and subnets.
An ANSI recommended standard for video transmission used to evaluate the quality of a received picture quality. Different requirements exist for short-haul, medium-haul, and long-haul RS-250C. Each of these three levels is defined by the number of intermediate processing devices and the type of path (optical or electrical). [Fib111] RSA
A public-key, or asymmetric, cryptographic algorithm that is used to provide the services of authentication and encryption. RSA stands for the three inventors of the algorithm; Rivest, Shamir, Adleman; also company by same name marketing public key technology. RSA Key Pair
A public/private key pair created for use with the RSA cryptographic algorithm.
RSVP Resource reSerVation Protocol
RTP/RTCP Real-time Protocol/Real-time Control Protocol
RTCP Real-time Control Protocol
RTP Real Time Protocol
Request to Send; in a communications network, a signal from a remote receiver to a transmitter for data to be sent to that receiver. [Fib111]
RTSP Real Time Streaming Protocol RZ
Return to Zero; a common means of encoding data that has two information states called “zero” and “one” in which the signal returns to a rest state during a portion of the bit period. [Fib111]
The reversal of a developed image due to the exposure of the partially developed image to actinic light. [Pho11]
The movement of the eye as it focuses on details of a scene. Some imaging systems mimic this movement by small, rapid scanning motions of the sensor. [Pho11]
A special-purpose polarimeter having a scale calibrated directly in the concentration of sugar in the test solution. [Pho11]
A term used to describe a saddle-shaped -- i.e., convex along one axis, concave along the other -- polished surface, generally an error, whose contours are apparent by the shape of Newton's rings. [Pho11]
Formula that describes the thermal equilibrium of gas electrons and ions as a direct function of variations in temperature. [Pho11]
A Sagnac interferometer (named after the French physicist Georges Sagnac) uses counterpropagating beams in a ring path, realized e.g. with multiple mirrors or with an optical fiber. If the whole interferometer is rotated e.g. around an axis which is perpendicular to the drawing plane, this introduces a relative phase shift of the counterpropagating beams (Sagnac effect). The sensitivity for rotations depends on the area covered by the ring, multiplied by the number of round trips (which can be large e.g. when using many turns in an optical fiber). It is possible e.g. to obtain a sensitivity which is sufficient for measuring the rotation of the Earth around its axis. Sagnac interferometers are used in inertial guidance systems. [Enc11]
SAID Security Association Identifier
In analog to digital signal processing; a sample is taken at regular intervals to establish the electrical potential (voltage) present in an analog system at a given point in time. Each sample is then assigned a digital value. In telephony, sample values are established by a codex, and range from zero to 255. (Though, for most “voice grade” connections the actual range of codex values is between zero and 127). Each sample value is transmitted across the digital phone network and used to re-create a facsimile of the original analog signal at the other end of a phone connection.
Sample and Hold Circuit
A device that acquires a signal and then stores it for a specified period of time before processing, and used, for example, to reduce noise as in correlated double sampling. [Pho11] Sample Rate
In analog to digital signal processing, the sample rate is the interval at which samples of an analog signal are taken. The sample rate for digital telephony, for example, is 8000 per second.
Unsigned applications and signed applications without a permission file have access to all the APIs for which there is no permission signaling defined. This is commonly called the sandbox.
Second Audio Program
SAP Service Access Point
The State Administration of Radio Film Television; an executive branch under the State Council of the People's Republic of China (PRC). Its main task is the administration and supervision of state-owned enterprises engaged in the television, radio, and film industries. The SARFT directly controls state-owned enterprises at the national level such as China Central Television, China National Radio, China Radio International, as well as other movie and television studios and other non-business organizations. The SARFT plays a similar role in China as TDF Group plays in France and Germany, or Crown Castle plays in the US or Australia. The SARFT owns and operates, as well as manages many thousands of microwave (MW), FM, TV and Shortwave relay transmitters in PRC (as well as those leased abroad for external broadcasting). The SARFT is also responsible for censoring any materials that might be objective to Chinese government or cultural standards. [Wik1116] Satellite
Device located in geostationary orbit above the earth which receives transmissions from separate points and retransmits them to cable systems, Direct Broadcast Satellite (DBS) receivers, and others over a wide area. Satellite Bands
Frequency ranges used in satellite communications. [PCM01]
Miscellaneous geosynchronous earth orbit (GEO); cable TV distribution (large 7 to 10 foot steerable dishes); satellite communications (SATCOM)
8 to 12
11 to 15
TV network satellite distribution; miscellaneous commsats
18 to 40
Miscellaneous commsats; satellite phone backhaul
Satellite Dish Antenna
A system for concentrating the weak signals sent from a satellite. Satellite Downlink
A data service that broadcasts data from an orbital satellite to terrestrial receivers. Used by some satellite TV vendors to provide a high-speed feed for receiving data from the Internet. Data sent to the Internet (Web page requests, outbound e-mail, etc.) must be sent by more conventional means, such as a dial-up modem connections to a local ISP.
Satellite Master Antenna Television System (SMATV)
Systems that serve a concentration of TV sets such as an apartment building, hotel, etc., utilizing one central antenna to pick up broadcast and/or satellite signals. Or RF distribution of satellite and antenna signals.
An electronic device capable of receiving satellite transmitted signals, downconverting and demodulating those signals, and providing a baseband output. [Arr11] Satellite Terminal
A receive-only satellite earth station consisting of an antenna reflector (typically parabolic in shape), a feedhorn, a low-noise amplifier (LNA), a down converter and a receiver. [Sat07] Saticon
A direct-readout television pickup tube. [Pho11] Saturable Absorber
A laser dye whose absorption coefficient drops at high levels of incident radiation. The phenomenon is often called bleaching. [Pho11] 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. [Fib111] Savart Plate
A double-plate device used to transmit polarized light and form interference fringes of the light, thus indicating its presence. It consists of two calcite plates of equal thickness, cut parallel to their natural cleavage faces and rotated and cemented together so that one is at right angles to the other. [Pho11]
1. A polariscope consisting of a Savart plate and a tourmaline plate analyzer, and used to produce parallel color fringes by transmitting polarized light. 2. A polariscope composed of an analyzing prism and Savart plate, and used with a theodolite to determine the neutral points of a source. [Pho11]
SAW (Surface Acoustic Wave) Filter
A solid state filter that yields a sharp transition between regions of transmitted and attenuated frequencies. [Arr11] S-Band
The wavelength region between 1485 nm and 1520 nm used in some CWDM and DWDM applications. [Fib111] SBS
Stimulated Brillouin Scattering; Brillouin scattering, named after Léon Brillouin, occurs when light in a medium (such as air, water or a crystal) interacts with time dependent optical density variations and changes its energy (frequency) and path. The density variations may be due to acoustic modes, such as phonons, magnetic modes, such as magnons, or temperature gradients. As described in classical physics, when the medium is compressed its index of refraction changes, and a fraction of the traveling light wave, interacting with the periodic refraction index variations, is deflected as in a three-dimensional diffraction grating. Since the sound wave, too, is travelling, light is also subjected to a Doppler shift, so its frequency changes. From a quantum point of view, Brillouin scattering is an interaction of light photons with acoustic or vibrational quanta (phonons), magnetic spin waves (magnons), or other low frequency quasiparticles interacting with light. The interaction consists of an inelastic scattering process in which a phonon or magnon is either created (Stokes process) or annihilated (anti-Stokes process). The energy of the scattered light is slightly changed, that is decreased for a Stokes process and increased for an anti-Stokes process. This shift, known as the Brillouin shift, is equal to the energy of the interacting phonon or magnon and thus Brillouin scattering can be used to measure phonon or magnon energies. The Brillouin shift is commonly measured by the use of a Brillouin spectrometer based on a Fabry–Pérot interferometer. [Wik115] SBS is a non-linear impairment that limits the maximum optical transmitted power that can be launched within a single-mode fiber (SMF), such as SMF-28, widely used within cable HFC networks and PON. The SBS threshold (SBSt) of ITU-T G.652 compliant SMF-28 is between +6 and +7 dBm at 1550nm wavelength. SBS bandwidth within SMF is approximately 20 MHz. Phase modulation of the optical transmitter is used to increase SBSt to approximately +16 dBm optical launch power using G.652 SMF-28 at 1550nm without suffering excessive CNR and CSO penalties. SBSt can also be increased through the use of fiber optic cable with greater than standard SBSt, such as Corning “G.652+” which offers a +3 dBm improvement in SBSt versus standard G.652 fiber at 1550nm. Another commonly employed technique within cable HFC networks and PONs is to launch high transmit optical power (e.g., from an Erbium Doped Fiber Amplifier (EDFA)) directly into a passive optical splitter. The passive optical splitter insertion loss helps to limit optical launch power to a level below SBSt. [Fre06] SC
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. [Fib111] Scalable Video
Refers to video compression that can handle a range of bandwidths, scaling smoothly over them. [Fib111]
A type of horn antenna feed which uses a series of concentric rings to capture signals that have been reflected toward the focal point of a parabolic antenna. [Sat07] Scalar Theory of Light
That theory that treats the light field as a single scalar field rather than as two coupled vector fields. [Pho11] Scaling Law
In coherence theory, an optical law put forth by physicist Emil Wolf that explains the behavior of light as it travels away from its source over large distances in space. Light spectra are assumed to remain uniform as light travels, but may change under certain circumstances. [Pho11] 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. [Fib111]
Scanning Acoustic Microscope (SAM)
Also called scanning laser acoustic microscope. A device that uses high-frequency ultrasound waves to penetrate surfaces. A scanning laser beam is used as a detector, which transmits information about subsurface defects to a television monitor for imaging. [Pho11]
A single continuous narrow strip of the picture area containing highlights, shadows, and halftones, determined by the process of scanning. Scanning Tunneling Microscope (STM)
A high-resolution imaging instrument that can detect and measure the positions of individual atoms on the surface of a material. A very fine conductive probe is placed at a distance of 10 to 20 Å above the surface of a conductive sample, and a bias voltage is applied between probe and surface during scanning, creating overlapping electron clouds and electrons that tunnel between the potential barrier between the probe and the sample. The probe tip is maintained at a constant distance from the sample by a piezoelectric transducer, yielding a three-dimensional topographical image. [Pho11] Scattering
The change in direction of light rays or photons after striking a small particle or particles. It may also be regarded as the diffusion of a light beam caused by the in homogeneity of the transmitting medium. [Arr11]
Scattering Diagram courtesy of Fiber Optics Info, http://www.fiber-optics.info/fiber_optic_glossary/s
SCCP Signaling Connection Control Part
S.CDMA Synchronous Code Division Multiple Access
Abbreviation for subcarrier multiplexing. The process by which multiple subcarrier signals are combined onto one signal. [Fib111]
SCN Switched Circuit Network
SCP Service Control Point Scramble
A signal security technique for rendering a TV picture unviewable, while permitting full restoration with a properly authorized decoder or descrambler.
A device used to electronically alter a signal so that it can only be viewed or heard on a receiver equipped with a special decoder. [Sat07] Also, 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%. [Fib111] Scrambling
A method of altering a signal identity to prevent unauthorized reception by persons not having decoders. [Arr11] SCSI
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. [Fib111]
SCTE Society for Cable Telecommunications Engineers; headquarted in Pennsylvania USA, near the birthplace of the cable industry in the USA, the SCTE is the cable industry’s society for “techies”, engineers, and technicians. The SCTE performs cable industry training and functions as a cable industry standards body, in cooperation with ANSI, Cable Labs, IEEE, ITU, EN, and other standards bodies. Annual membership fee is $45 US as of CY 2011. Anyone with interest in the cable industry and its technology should join. The other major trade organization within the cable industry in the USA is the National Cable Telecommunications Association (www.ncta.com), which is the USA cable industry’s trade organization with primary focus for content providers and legal professionals. The NCTA is based in Washington, D.C. and lobbies for cable industry interests, goals, and rights against all comers. Link to the SCTE web site: www.scte.org.
SCTP Stream Control Transmission Protocol
SD Secure Digital
Synchronous Digital Hierarchy
SDMA Spatial Division Multiple Access
SDP Session Description Protocol
Software Defined Radio; radio in which some or all of the physical layer functions are software defined. Also known as Software Radio. The Wireless Innovation Forum, working in collaboration with the Institute of Electrical and Electronic Engineers (IEEE) P1900.1 group, has worked to establish a definition of SDR that provides consistency and a clear overview of the technology and its associated benefits. A radio is any kind of device that wirelessly transmits or receives signals in the radio frequency (RF) part of the electromagnetic spectrum to facilitate the transfer of information. In today's world, radios exist in a multitude of items such as cell phones, computers, car door openers, vehicles, and televisions. Traditional hardware based radio devices limit cross-functionality and can only be modified through physical intervention. This results in higher production costs and minimal flexibility in supporting multiple waveform standards. By contrast, software defined radio technology provides an efficient and comparatively inexpensive solution to this problem, allowing multi-mode, multi-band and/or multi-functional wireless devices that can be enhanced using software upgrades. SDR defines a collection of hardware and software technologies where some or all of the radio’s operating functions (also referred to as physical layer processing) are implemented through modifiable software or firmware operating on programmable processing technologies. These devices include field programmable gate arrays (FPGA), digital signal processors (DSP), general purpose processors (GPP), programmable System on Chip (SoC) or other application specific programmable processors. The use of these technologies allows new wireless features and capabilities to be added to existing radio systems without requiring new hardware. [Wir11]
Standard Definition Television
SDU Service Data Unit SDV
Switched Digital Video; an open internet protocol (IP) architecture that permits real-time subscriber monitoring (usually via use of an out-of-band (OOB) channel or channels) of content usage and the ability for a cable operator headend (HE) or hub to selectively deliver content based on real-time usage. Switched Digital Video (SDV) allows cable providers the ability to save bandwidth by sending requested channels on an “as needed” basis to users one at a time. Cable operators can potentially offer a greater number of channel offerings to compensate for not having to broadcast unwatched programs when not required to do so. SDV compresses multiple standard definition television (SDTV) or HDTV broadcast streams into MPEG-2/MPEG-4 video through Quadrature Amplitude Modulation (QAM) techniques. SDV services are typically reserved for hybrid fiber-coaxial (HFC) networks where highest data rates can be achieved (for future expansion of SDV networks). Cable providers can consume typically from 50% to 75% less bandwidth compared to traditional broadcast services by multiplexing ten (10) SDTV broadcasts per 6MHz RF channel (typical). MPEG-4 encoding can yield a greater number of channels, however with reduced video quality.