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

Pertaining to the logical structure for communications networks standardized by the International Organization for Standardization (ISO)

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Pertaining to the logical structure for communications networks standardized by the International Organization for Standardization (ISO). [Fib111]
Operating System (OS)
The software that manages hardware and resources on a computer. Applications use the operating system to make requests for services and interact with the computer's devices. Or the software that controls the underlying hardware, performs the most basic functions for managing the resources of the hardware, and provides services to other software such as applications.

Operation Systems Support (OSS)
The back office software used for configuration, performance, fault, accounting and security management.

Optical Add/Drop Multiplexer (OADM)

A device which adds or drops individual wavelengths from a DWDM system. [Fib111]

OADM Diagram courtesy of Fiber Optics Info, http://www.fiber-optics.info/fiber_optic_glossary/o

Optical Amplifier

A device that amplifies an input optical signal without converting it into electrical form. The best developed are optical fibers doped with the rare earth element, erbium. See also EDFA. [Fib111]

Optical Amplifier Block Diagram courtesy of Fiber Optics Info, http://www.fiber-optics.info/fiber_optic_glossary/o

Optical Bandpass

The range of optical wavelengths which can be transmitted through a component. [Fib111]
Optical Bands

The spectrum for transmission in single mode optical fibers has been broken into the following wavelength ranges, or bands (defined by ITU-T). Typically, the wavelengths transmitted in multimode fibers are between 850 and 1310 nm, known originally as first window and second window. [PCM01]



Wavelength, λ, Range in Nanometers (nm)



1260 to 1360



1360 to 1460



1460 to 1530



1530 to 1565



1565 to 1625



1625 to 1675

Optical Cable

A fiber, multiple fibers, or fiber bundle in a structure fabricated to meet optical, mechanical, and environmental specifications. [Arr11]
Optical Channel

An optical wavelength band for WDM optical communications. [Fib111]

Optical Channel Spacing

The wavelength separation between adjacent WDM channels. [Fib111]

Optical Channel Spacing Diagram courtesy of Fiber Optics Info, http://www.fiber-optics.info/fiber_optic_glossary/o

Optical Channel Width

The optical wavelength range of a channel. [Fib111]
Optical Connector Loss

The signal loss through the connector (insertion loss), often expressed in decibels (dB), caused by impedance mismatching, impurities or structural changes that cause reflections and/or absorption to a signal that is passing through the connector. [Opt09]
Optical Continuous Wave Reflectometer (OCWR)

An instrument used to characterize a fiber optic link wherein an unmodulated signal is transmitted through the link, and the resulting light scattered and reflected back to the input is measured. Useful in estimating component reflectance and link optical return loss. [Fib111]


Optical Detector

A transducer that generates an output electrical signal when irradiated with optical power. [Arr11]
Optical Directional Coupler (ODC)

A component used to combine and separate optical power. [Fib111]
Optical Distance

The actual length of the light path in a substance divided by the refractive index of that substance. [Pho11]
Optical Fall Time

The time interval for the falling edge of an optical pulse to transition from 90% to 10% of the pulse amplitude. Alternatively, values of 80% and 20% may be used. [Fib111]

Pulse Waveform Diagram courtesy of Fiber Optics Info, http://www.fiber-optics.info/fiber_optic_glossary/o

Optical Fiber
An extremely thin, flexible thread of pure glass, able to carry one thousand times the information possible with traditional copper wire. Or, any filament or fiber, made of dielectric materials that guide light, whether or not it is used to transmit signals. [Arr11]

Optical Isolator

A component used to block out reflected and unwanted light. Also called an isolator. [Fib111]

Optical Isolator Diagram courtesy of Fiber Optics Info, http://www.fiber-optics.info/fiber_optic_glossary/o

Optical Link

Any optical transmission channel designed to connect two end terminals or to be connected in series with other channels. [Arr11]
Optical Link Loss Budget

The range of optical loss over which a fiber optic link will operate and meet all specifications. The loss is relative to the transmitter output power and affects the required receiver input power.  [Fib111]
Optical MEMS Mirror

A popular method for optical switching, micro-electrical mechanical systems (MEMS), uses tiny arrays of tilting mirrors. Controlled electrical signals are used to adjust the arrays of mirrors to the proper angle, allowing for the desired output signal to appear on the correct port. The diagram below illustrates the MEMS mirror used in one manufacturer's optical switch. MEMS-based systems allow higher port-count switches than competing technologies. [IEC06]

Optical MEMS Mirror used in an Optical Switch, courtesy of J. Ford, J. Walker, and K. Goosen, "Optical MEMS: Overview and MARS Modulator," Presentation made by Lucent Technologies, http://www.iec.org/newsletter/jan06_2/broadband_1.html

Optical Modulation Index (OMI)

The amount that the instantaneous power of the optical carrier varies around the average power of that optical carrier. Within the RFoG specification SCTE 174 2010, OMI is used only for the amplitude modulation of an optical carrier by an RF signal and is generally expressed as a percent. OMI is defined to be 100% when the peak of a single sine wave that is amplitude modulated onto an optical carrier modulates the instantaneous power of that carrier from zero power to twice the average power.

OMI Definition, from SCTE 174 2010, “Radio Frequency over Glass Fiber-to-the-Home Specification

In the optical domain, the OMI is defined as: OMI = (Pp – Pt) / Pt, where

  • Pp is the peak optical output power of the laser

  • Pt is the optical power at the bias current

In the electrical domain, the OMI is defined as: OMI = Ip / (Ib – Ith), where

  • Ith is the threshold current of the laser

  • Ib is bias current

  • Ip is the peak modulating current

The optical and electrical definitions are equivalent. The definition of OMI involves the peak of the signal and is easiest to measure with a simple sinusoidal signal. The OMI of any other modulating signal, m (t), is defined to be the OMI that would be produced if a single sine wave of identical average RF power to m (t) were modulated onto the optical carrier. In other words, with a complex modulating signal, the exact peak is no longer referenced. The average power of the complex signal is measured and is said to have the same OMI as would be produced if that signal were replaced with a sine wave of equivalent average power. OMI should always be measured with a CW carrier that has the same average power as the desired signal. Unless specified as a per-channel value, OMI always refers to the modulation index of the entire RF signal.[SCT11]. Link to SCTE sponsored primer on OMI: http://www.scte.org/mmpres/Primer/omi/
Optical Modulators

A device which can be used for manipulating a property of light – often of an optical beam, e.g. a laser beam. Depending on which property of light is controlled, modulators are called intensity modulators, phase modulators, polarization modulators, spatial light modulators, etc. A wide range of optical modulators are used in very different application areas, such as in optical fiber communications, displays, for active Q switching or mode locking of lasers, and in optical metrology.

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