Wired Broadband and Related Industry Glossary of Terms with Acronyms As of 13 June 2011 Compiled By: Conrad L. Young, Director, Broadband Technical Strategy

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Optical Carrier level n. The optical carrier rate of a synchronous optical network (SONET). [Arr11]

Optical Carrier level with integer; a carrier rate specified in the SONET standard. [Fib111]

SONET/SDH Designations, including Optical Carrier Level, OC-x, and Bandwidths

SONET Optical Carrier Level

SONET Frame Format

SDH level and Frame Format

Payload bandwidth[nb 3] (Kbit/s)

Line Rate (Kbit/s)









































  • Telcordia GR-253-CORE, SONET Transport Systems: Common Generic Criteria

  • Telcordia GR-499-CORE, Transport Systems Generic Requirements (TSGR): Common Requirements

  • ANSI T1.105: SONET - Basic Description including Multiplex Structure, Rates and Formats

  • ANSI T1.119/ATIS PP 0900119.01.2006: SONET - Operations, Administration, Maintenance, and Provisioning (OAM&P) - Communications

  • ITU-T recommendation G.707: Network Node Interface for the Synchronous Digital Hierarchy (SDH)

  • ITU-T recommendation G.783: Characteristics of synchronous digital hierarchy (SDH) equipment functional blocks

  • ITU-T recommendation G.803: Architecture of Transport Networks Based on the Synchronous Digital Hierarchy (SDH)

Outlet Digital Adapter [Arr11]


Optical Distribution Network; term for optical networks being developed for interactive video, audio, and data distribution. [Fib111]

Open Digital Rights Language Initiative


Optical Electrical Converter

Opto-Electronic Integrated Circuit; an integrated circuit that includes both optical and electrical elements. [Fib111]
Original Equipment Manufacturer


Orthogonal Frequency Division Multiplex; a digital transmission technique that uses a large number of carriers spaced apart at slightly different frequencies. First promoted in the early 1990s for wireless LANs, OFDM is used in many wireless applications including Wi-Fi, WiMAX, LTE, ultra-wideband (UMB), as well as digital radio and TV broadcasting in Europe and Japan. It is also used in land-based ADSL (see OFDMA). Although frequency division multiplexing (FDM) implies multiple data streams, orthogonal FDM carries only one data stream broken up into multiple signals. Hundreds or thousands of carriers, known as "subcarriers," are used for a single data channel. Multiple subcarriers enable the receiver to more easily detect the signals in environments with multipath and other interference. In addition, each subcarrier can transmit a lower-speed signal, all of which are aggregated at the receiving side into the original high-speed signal. Lower speed signals are also more easily deciphered at the receiving end. OFDM subcarriers can be modulated by any method, although QAM and QPSK are typically used (see QAM and PSK). Coded OFDM (COFDM) adds forward error correction. [PCm11]


Refers to the reception of television broadcast signals transmitted over the air and received through the use of either a log-periodic or yagi type antenna. Synonymous with over-the-air. [Arr11]
Off the Air
Reception of a TV signal that has been broadcast through the air.

Office of Telecommunications Policy (OTP)
Division of the staff of the Executive Office of the President that advises the Executive Branch on communications policy, studies policy questions, and develops legislative proposals.

Off-Net Call
A communication connecting a PacketCable subscriber to a user on the PSTN.


The frequency separation between inbound and outbound carriers on the same communication channel. Typically 192.25 MHz. [Arr11]


The Office of Telecommunications of the United Kingdom government. This unit a part of the Department of Industries regulates telecommunications in the United Kingdom. [Sat07]
The standard unit of resistance, reactance and impedance. A resistant of 1 ohm will conduct 1 ampere of current when a voltage of 1 volt is placed across it.

Ohm's Law

Stated E = IR, I = E/R or R = E/I, the current I in a circuit is directly proportional to the voltage E and inversely proportional to the resistance R. [Arr11]

Object Identification


Optical Line Interface Unit. The optical transceiver. [Arr11] Also referred to as the OLT.


Optical Line Termination; optical network elements that terminate a line signal. [Fib111]

Optical Loss Test Set; a source and optical power meter combined used to measure optical loss. [Fib111]

Optical Multiplex Section; a section of a DWDM system that incorporates an optical add/drop multiplexer (OADM). [Fib111]
On-demand Service
A type of telecommunication service in which the communication path is established almost immediately in response to a user request brought about by means of a user-network signaling.

One-way Hash
A hash function that has an insignificant number of collisions upon output.

One-Way System
The ability to receive TV programming through the broadband network. Customers wanting to order movies and other services must use traditional methods to do so rather than using the two-directional interactive capabilities offered through the Two-Way System. As the physical plant is upgraded, one-way systems will be replaced by two-way systems.


Optical Network Interface; a device used in an optical distribution network to connect two parts of that network. [Fib111]
On-Net Call
A communication placed by one customer to another customer entirely on the PacketCable Network.


Optical Network Unit; IEEE terminology for the optical network element that terminates a line signal in installations where the fiber extends into the customer premises. [Fib111] Optical Network Unit (ONU) is the generic name for a device installed at a subscriber’s premises to convert fiber access interfaces to Ethernet, plain old telephone system (POTS), and other interfaces, whether the device is serving one or more subscribers. [FTT09] In a PON the fiber link is terminated in the central office at an Optical Line Terminal or OLT. OLT devices are the semiconductors that perform that function. They interface to the fiber link connecting the central office equipment to the customer premises equipment or CPE. In the CPE, the fiber link is terminated by an Optical Network Unit, or ONU, or by an Optical Network Terminal, or ONT. These terms have the same meaning, but ONU is IEEE terminology and ONT is ITU-T terminology. The acronym R-ONU is used to describe the RF over Glass (RFoG) optical network unit in an effort to differentiate the device from those employed in other forms of passive optical networks. [SCT11]

Optical Network Termination; ITU-T terminology for a network element that is part of a fiber-in-the-loop system. [Fib111] In common usage, an Optical Network Terminal (ONT) serves a single subscriber premises such as a stand-alone house. An ONT has no need for security between its few interfaces and sells for perhaps a few hundred dollars. A typical indoor ONT is shown below. [FTT09]

ONT Photograph courtesy of FTTxtra dot com, http://www.fttxtra.com/ftth/onu-or-ont/

Out-Of-Band (OOB) Channel.
The OOB receive circuit typically in use today is intended for use within cable and SATCOM-DBS industry STBs, TVs of all types except hand-held mobile devices, DOCSIS® Set-top Box Gateways (DSGs), residential gateways (RGs), some FTTx ONU/ONTs, and some CATV HE equipment, is specified via two ANSI/SCTE specifications,  ANSI/SCTE 55-1 2002  and ANSI/SCTE 55-2 2002 and is referenced within Data-Over-Cable Service Interface Specifications (DOCSIS)  "DOCSIS Set-top Gateway (DSG) Interface Specification, CM-SP-DSG-I14-090529.  It is important to note that the ANSI/SCTE specifications are issued by a body with no legislative authority.  OEMs comply with these specifications voluntarily. The ANSI/SCTE OOB specifications detail both receive (downstream, DS) and return (upstream, US) path architectures.  The referenced specifications were under review and published nearly in parallel with original DOCSIS® 1.0 specifications.  DOCSIS® adopted the ANSI/SCTE OOB return path specifications nearly in their entirety as the "baseline" lowest performance level and highest reliability set of upstream (US) physical (PHY) layer and RF transmission specifications.  QPSK modulation, in the form described in the ANSI/SCTE OOB specifications, is employed by all DOCSIS® 1.x, 2.0, and 3.0 compliant modems when operating in its lowest performance, highest reliability mode.  Fielded CPE utilizing a dedicated OOB return path is uncommon today, but will be a key component in devices within some HFC networks utilizing switched digital video (SDV) architectures and features.  Cisco S-A and Big Band Networks SDV topologies rely on an OOB signalling path for critical HFC network signalling between the HE or hub and connected CPE.  One would logically expect future generation Cisco S-A STBs, CMs, DSGs, RGs, and related devices to be equipped with both an OOB receive (for downstream, DS) and OOB transmit (for upstream, US) set of circuits.[CLY09]

ANSI/SCTE 55-1 2009, Digital Broadband Delivery System: Out of Band Transport Part 1: Mode A specifies the Physical Layer and the Data Link Layer (including the MAC Layer) of the Out-Of-Band (OOB) cable system transport. Section 5 describes the Physical Layer protocol. Section 6 describes the Data Link Layer protocol.

ANSI/SCTE 55-2 2008, Digital Broadband Delivery System: Out of Band Transport Part 2: Mode B specifies the OOB Physical Layer (PHY) Interface supporting transmission over radio frequency coax (up to 1GHz bandwidth). The OOB PHY Interface is referred to as the bi-directional QPSK-link on HFC (Hybrid Fiber Coax). This Physical Layer Interface describes the complete physical layer structure, i.e. framing structure, channel coding and modulation for each direction Downstream and Upstream). For the downstream, QPSK modulation channel Grade A is mandatory and Grade B is optional. For the upstream, QPSK channel Grade B is mandatory and Grades A and C are optional.

Spectrum Allocation For the Bi-directional PHY on Coax

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