Glossary
`
`A bsorption Conversion o f light energy into
`another form by a material. Not equal to loss or
`attenuation, which includes scattering.
`
`Acceptance Angle The angle over which the core
`of an optical fiber accepts incoming light; usually
`measured from the fiber axis. Related to numerical
`aperture (NA).
`
`Access Network Part of the telecommunication net-
`work that connects to individual and corporate users.
`
`Active Component A component that requires
`external power.
`
`Add-Drop Multiplexer A device that drops and/or
`adds one or more optical channels to a signal.
`
`AD SL (Asymmetric Digital Subscriber Line) A
`type of DSL with more bandwidth downstream (to
`the subscriber) than upstream.
`
`5 bytes of header information followed by 48 data
`bytes.
`
`Attenuation Reduction of the magnitude of an
`optical signal by any means, including absorption of
`energy or scattering of light. Measured in decibels per
`unit length.
`
`Attenuator An optical device that reduces the
`intensity of transmitted light.
`
`Avalanche Photodiode (APD) A semiconductor
`photodetector with integral detection and amplifica-
`tion stages. Electrons generated at a pin junction are
`accelerated in a region where they free an avalanche
`of other electrons. APDs can detect faint signals but
`require higher voltages than other semiconductor
`electronics.
`
`Average Power The average level of power in a sig-
`nal that varies with time.
`
`A ll-D ielectric C able Cable made entirely of
`dielectric (insulating) materials without any metal
`conductors, armor, or strength members.
`
`AW G See Waveguide Array.
`
`Axis The center of an optical fiber.
`
`Analog A signal that varies continuously (e.g.,
`sound waves). Analog signals have frequency and
`bandwidth measured in hertz.
`
`Angstrom (A) A unit of length equal to 0.1 nm.
`
`Backbone System A transmission network that car-
`ries high-speed telecommunications between regions
`(e.g., a nationwide long-distance telephone system).
`Sometimes used to describe the part of a local area net-
`work that carries signals between branching points.
`
`ATM (Asynchronous Transfer Mode) A digital
`transmission switching format, with cells containing
`
`Backscattering Scattering of light in the direction
`opposite to that in which it was originally traveling.
`
`MASIMO 2014
`PART 12
`Apple v. Masimo
`IPR2020-01526
`
`

`

`Glossary
`
`Information capacity. In analog sys-
`Bandwidth
`tems, bandwidth is the range of frequencies trans-
`mitted; in digital systems, it is the data rate.
`
`In technology, the wave that is modulated
`Carrier
`with a signal carrying information. In business, a
`company that provides telecommunication services.
`
`Baud Strictly speaking, the number of signal-level
`transitions per second in digital data. For some com-
`mon coding schemes, this equals bits per second, but
`this is not true for more complex coding, and it is
`often misused. Bits per second is less ambiguous.
`
`Beamsplitter A device that divides incident light
`into two separate beams.
`
`B idirectional Operating in both directions.
`Bidirectional couplers split or combine light the same
`way when it passes through them in either direction.
`Bidirectional transmission sends signals in both
`directions, sometimes through the same fiber.
`
`Birefringent Having a refractive index that differs
`for light of different polarizations.
`
`Bit Error Rate (BER) The fraction of bits trans-
`mitted incorrectly.
`
`Bragg Scattering Scattering of light caused by a
`change in refractive index, as used in fiber Bragg gratings
`and distributed Bragg reflectors.
`
`Broadband Covering a wide range of frequencies or
`having a high data rate. Broadband Internet service,
`including fiber to the home, DSL and cable modems,
`has a much higher data rate than dial-up service.
`
`Broadcast Transmission Sending the same signal
`to many different places, like a television broadcast-
`ing station. Broadcast transmission can be over opti-
`cal fibers if the same signal is delivered to many
`subscribers.
`
`Bundle (of fibers) A rigid or flexible group of
`fibers assembled in a unit. Coherent fiber bundles
`have fibers arranged in the same way on each end and
`can transmit images.
`
`Byte Eight bits of digital data. (Sometimes parity
`and check bits are included, so one “byte” may include
`10 bits, but only 8 of them are data.)
`
`Category 5 A type of twisted-pair copper cable
`designed to transmit high-speed signals.
`
`C A T V An acronym for cable television, derived
`from Community Antenna Tele Vision.
`
`C-Band Wavelengths of 1530 to 1565 nm, where
`erbium-doped fiber amplifiers have their strongest
`gain. Normally erbium-fiber amplifiers operate in
`either C- or L-band.
`
`Cell A fixed-length data packet transmitted in cer-
`tain digital systems such as ATM. Also the area
`served by one cellular phone tower, and sometimes
`slang for a cellular telephone.
`
`Central Office A telephone company facility for
`switching signals among local telephone circuits;
`connects to subscriber telephones. Also called a
`switching office.
`
`C h ann el A distinct signal in a transmission
`medium. Optical channels are signals transmitted
`through the same fiber at different wavelengths.
`
`Chirp A variation in optical wavelength that arises
`from directly modulating a diode laser source.
`
`Chrom atic Dispersion Wavelength-dependent
`pulse spreading in optical fibers, measured in
`picoseconds (of pulse spreading) per nanometer (of
`source bandwidth) per kilometer (of fiber length). It
`is the sum of waveguide and material dispersion.
`
`C ircuit Originally a physical connection that
`transmits electricity or signals. Now also a communi-
`cation channel that guarantees a fixed transmission
`capacity.
`
`Circuit Switching Making temporary physical or
`virtual connections between two points, which guar-
`antees a fixed transmission capacity.
`
`Cladding The layer of glass or other transparent
`material surrounding the light-carrying core of an
`
`

`

`Glossary
`
`optical fiber. It has a lower refractive index than the
`core and thus confines light in the core. Coatings
`may be applied over the cladding.
`
`Critical Angle The angle at which light in a high-
`refractive-index material undergoes total internal
`reflection.
`
`C LE C (Competitive Local Exchange Carrier) A
`company that offers local telephone service in com-
`petition against dominant phone companies.
`
`Coarse W a v e le n g th -D iv isio n M u ltip le x in g
`(CW DM ) Transmitting signals at multiple wave-
`lengths through the same fiber with wide spacing
`between optical channels. Standard spacing is
`20 nanometers.
`
`Coating An outer plastic layer applied over the
`cladding of a fiber for mechanical protection.
`
`Coax Coaxial cable— cable with a central metallic
`conductor surrounded by an insulator that is covered
`by a metallic sheath that runs the length of the cable.
`
`Fibers packaged
`Coherent Bundle (of fibers)
`together in a bundle so they retain a fixed arrange-
`ment at the two ends and can transmit an image.
`
`Compression Reducing the number of bits needed
`to encode a digital signal, typically by eliminating
`long strings of identical bits or bits that do not change
`in successive sampling intervals (e.g., video frames).
`
`Connector A device mounted on the end of a
`fiber-optic cable, light source, receiver, or housing
`that mates to a similar device to couple light into and
`out of optical fibers. A connector joins two fiber
`ends, or one fiber end and a light source or detector.
`
`Industry slang for metal wire, either
`Copper
`twisted-pair or coaxial cable.
`
`Core The central part of an optical fiber that
`guides light.
`
`Coupler A device that connects three or more
`fiber ends, dividing one input between two or more
`outputs or combining two or more inputs into one
`output.
`
`Coupling Transfer of light into or out of an optical
`fiber. (Note that coupling does not require a coupler.)
`
`Cut-Back Measurement Measurement of optical
`loss, made by cutting a fiber. It compares loss of a
`short segment with loss of a longer one.
`
`C u to ff Wavelength The longest wavelength at
`which a single-mode fiber can transmit two modes,
`or (equivalently) the shortest wavelength at which a
`single-mode fiber carries only one mode.
`
`Cycles per Second The frequency of a wave, or
`number of oscillations it makes per second. One
`cycle per second equals one hertz.
`
`Dark Current The noise current generated by a
`photodiode in the dark.
`
`Dark Fiber Optical fiber installed without transmit-
`ter and receiver, usually to provide expansion capacity.
`Some carriers lease dark fibers to other companies that
`add equipment to transmit signals through them.
`
`Data Link A fiber system transmitting digital data
`between two points.
`
`dBm Decibels relative to 1 mW.
`
`dBp Decibels relative to 1 pW.
`
`D B R See Distributed Bragg Reflection.
`
`Decibel (dB) A logarithmic comparison of power
`levels, defined as ten times the base-10 logarithm of
`the ratio of the two power levels. One-tenth of a bel.
`
`Demultiplexer A device that separates a multi-
`plexed signal into its original components; the
`inverse of a multiplexer.
`
`D ense W a v e le n g th -D iv isio n M u ltip le x in g
`(DW DM ) Transmitting signals at multiple closely
`spaced wavelengths through the same fiber. Channel
`spacing is usually 200, 100, or 50 GHz, correspon-
`ding to about 1.6, 0.8, or 0.4 nm respectively.
`
`Detector A device that generates an electrical sig-
`nal when illuminated by light. The most common
`fiber-optic detectors are photodiodes.
`
`

`

`Glossary
`
`DFB See Distributed Feedback.
`
`Dielectric Nonconductive.
`
`Dielectric Filter An optical filter that selectively
`transmits one wavelength and reflects others based on
`interference effects inside the structure. Also called
`interference filter.
`
`Digital Encoded as a signal in discrete levels, typi-
`cally binary Is and Os.
`
`D igital Subscriber Line (DSL) A service that
`transmits digital signals to homes at speeds of hun-
`dreds of kilobits to tens of megabits per second over
`twisted-pair wires at higher frequencies than voice
`telephone signals. There are several variations.
`
`Diode An electronic device that lets current flow in
`only one direction. Semiconductor diodes used in
`fiber optics contain a junction between regions of
`different doping. They include light emitters (LEDs
`and laser diodes) and detectors (photodiodes).
`
`Diode Laser A semiconductor diode that generates
`laser light. A current flowing through the diode
`causes electrons and holes to recombine at the junc-
`tion layer between p- and M-doped regions, produc-
`ing excited states that can release energy in the form
`of light.
`
`Directional Coupler A coupler in which light is
`transmitted differently when it goes in different
`directions.
`
`Discrimination Circuit Electronics that decide
`whether a digital signal is a 1 or a 0.
`
`Dispersion The stretching of light pulses as they
`travel in an optical fiber, which increases their
`duration.
`
`Dispersion Com pensation Typically, adding
`fibers or other components with chromatic disper-
`sion that offsets the chromatic dispersion of a fiber-
`optic transmission line. Compensation is also
`possible for polarization-mode dispersion, but it is
`more difficult and rarely needed. Electronic disper-
`sion compensation is also possible.
`
`Dispersion-Shifted Fiber Optical fiber with nomi-
`nal wavelength of zero chromatic dispersion shifted
`away from 1310 nm. Sometimes used for zero disper-
`sion-shifted fiber, which has zero chromatic disper-
`sion at 1550 nm and is not used in DWDM systems.
`Dispersion Slope The change in chromatic disper-
`sion with wavelength.
`
`Distributed Bragg Reflection Reflection of light
`caused by periodic changes in refractive index in a stack
`of layers of different composition or— equivalendy—
`by a corrugation at the boundary between two semi-
`conductor layers. The period and the refractive index
`select one wavelength.
`D istributed Feedback Feedback arising from
`reflection distributed through a structure.
`Distributed-Feedback Laser A diode laser with a
`corrugation in the electrically pumped part of the
`laser, which selects the laser wavelength by reflecting
`that wavelength back into the active layer.
`
`Doping Addition of small quantities of an impu-
`rity to a material to provide desired characteristics.
`Semiconductors are doped to produce the desired
`concentration of current carriers.
`
`Drop A cable that delivers service to an individual
`customer.
`D SL See D igital Subscriber Line.
`
`D T V Digital television.
`In cables, one that contains two fibers. For
`Duplex
`connectors, one that connects two pairs of fibers. For
`data transmission, full-duplex transmitters and
`receivers simultaneously send and receive signals in
`both directions, but half-duplex cannot do both at
`the same time.
`D W DM See Dense Wavelength-Division Multiplexing.
`
`Edge-Emitting Diode An LED that emits light
`from its edge, producing more directional output
`than LEDs that emit from their top surface.
`
`Edge-Emitting Laser A semiconductor laser that
`emits light in the plane of its junction from the edge
`of the chip.
`
`

`

`Electro-Absorption Modulator A semiconductor
`diode reverse-modulated so it modulates light passing
`through it.
`
`Electromagnetic Interference (EMI) Noise gener-
`ated when stray electromagnetic fields induce currents
`in electrical conductors.
`
`Electromagnetic Radiation Waves made up of
`oscillating electrical and magnetic fields perpendicu-
`lar to one another and traveling at the speed of light.
`Can also be viewed as photons or quanta of energy.
`Electromagnetic radiation includes radio waves,
`microwaves, infrared, visible light, ultraviolet radiation,
`X rays, and gamma rays.
`
`EM I See Electromagnetic Interference.
`
`Endoscope A fiber-optic bundle used for imaging
`and viewing inside the human body.
`
`Erbium Band The range of wavelengths where
`erbium-doped fiber amplifiers are used, from 1530 to
`1610 nm.
`
`Erbium-Doped Fiber Amplifier (EDFA) Optical
`fiber doped with the rare earth element erbium,
`which can amplify light at 1530 to 1610 nm when
`pumped by an external light source.
`
`Ethernet A local-area network standard. The orig-
`inal Ethernet transmits 10 Mbit/s. Other versions
`are Fast Ethernet at 100 Mbit/s, Gigabit Ethernet at
`1 Gbit/s, and 10-Gigabit Ethernet.
`
`Evanescent Wave Guided light waves that extend
`beyond the boundary of a fiber core into the cladding.
`Evanescent waves can transfer energy between wave-
`guides.
`
`Excess Loss Loss of a passive coupler above that
`inherent in dividing light among the output ports.
`
`External Modulation Modulation of output of a
`light source by an external device.
`
`Extrinsic Loss Splice losses arising from the splic-
`ing process itself.
`
`Eye Pattern A pattern formed by overlaying traces
`of a series of transmitted pulses in a visual display.
`
`Glossary
`
`The more open the eye, the sharper the distinction
`between on and off pulses.
`
`Fabry-Perot A resonant cavity formed by a pair of
`mirrors aligned parallel to each other. A Fabry-Perot
`laser is a diode laser with its edge facets cleaved so
`they form a Fabry-Perot cavity.
`
`Ferrule A tube within a connector with a central
`hole that contains and aligns a fiber.
`
`Fiber Amplifier An optical fiber doped to amplify
`light from an external source. The most important
`type is the erbium-doped fiber amplifier.
`
`Fiber Bragg Grating An optical fiber in which the
`core refractive index varies periodically along its
`length, causing Bragg scattering at wavelengths
`selected by the period and refractive index. A fiber
`Bragg grating reflects the selected wavelength and
`transmits others.
`
`Fiber Distributed Data Interface (FDDI) A stan-
`dard for a 100-Mbit/s fiber-optic local-area network.
`
`Fiber-Optic Gyroscope A coil of optical fiber that
`can detect rotation about its axis.
`
`Fiber to the Curb (FTTC) Fiber-optic service to a
`node that is connected by wires to several nearby
`homes, typically on a block.
`
`Fiber to the Home (FTTH) A network in which
`optical fibers bring signals all the way to homes.
`
`Fiber to the Premises (FTTP) Distribution of
`signals through fiber optics all the way to individual
`residences. Functionally the same as fiber to the
`home.
`
`Fibre Channel A standard for data transmission
`among storage devices and computers over fiber or
`copper.
`
`FITL Fiber in the loop.
`
`Fluoride Glasses Materials that have the amor-
`phous structure of glass but are made of fluoride
`compounds (e.g., zirconium fluoride) rather than
`oxide compounds (e.g., silica).
`
`

`

`Glossary
`
`Forward Error Correction Adding extra bits to a
`block of data bits to detect and correct errors in trans-
`mission.
`
`Frame A fixed-length block of data transmitted as
`a unit; SONET transmits frames. In video, one of a
`series of images shown in sequence.
`
`Free-Space O ptics Light signals transmitted
`through air rather than fibers.
`
`Frequency The number of times an electromagnetic
`wave oscillates in a second, or the number of wave
`peaks that pass a point in a second; measured in hertz.
`
`Frequency-Division M ultiplexing Combining
`analog signals by assigning each a different carrier
`frequency and merging them in a single signal with a
`broad range of frequencies.
`
`FTT C See Fiber to the curb.
`
`FTTH See Fiber to the home.
`
`FTTP See Fiber to the Premises.
`
`In data transmission, transmitters
`Full-Duplex
`and receivers that simultaneously send and receive
`signals in both directions.
`
`Fused Fibers A bundle of fibers melted together so
`they maintain a fixed alignment with respect to each
`other in a rigid rod.
`
`Fusion Splice A splice made by melting the tips of
`two fibers together so they form a solid junction.
`
`Gain The increase in signal strength as light passes
`through an amplifying medium.
`
`Gallium Aluminum Arsenide (GaAlAs) A semi-
`conductor compound used in LEDs, diode lasers,
`and certain detectors.
`
`Gallium Arsenide (GaAs) A semiconductor com-
`pound used in LEDs, diode lasers, detectors, and
`electronic components.
`
`Gbit/s Gigabits (billion bits) per second.
`
`Glass A solid in which the atoms are arranged ran-
`domly instead of ordered in a crystal. In fiber optics,
`
`“glass” usually means a silica compound unless other-
`wise noted.
`
`Graded-index Fiber A fiber in which the refractive
`index changes gradually with distance from the fiber
`axis, rather than abruptly at the core-cladding interface.
`
`Graded-index Fiber Lens A short segment of
`graded-index fiber that focuses light passing through it.
`
`Granularity How finely a signal can be broken
`into its component parts.
`
`Group Delay Time The difference in travel time
`through a fiber for light of different wavelengths.
`
`In data transmission, a system in
`H alf-D upl ex
`which transmitters and receivers cannot simultane-
`ously send and receive signals.
`
`Hard-Clad Silica Fiber A fiber with a hard plastic
`cladding surrounding a step-index silica core. (Other
`plastic-clad silica fibers have a soft plastic cladding.)
`
`Harmonic Frequency A frequency that is an inte-
`gral multiple of a base frequency.
`
`H D T V High-definition (or high-resolution) televi-
`sion; digital television with higher resolution than
`present analog systems.
`
`Head-End The central facility where signals are
`combined for distribution in a cable television system.
`
`Hertz Frequency in cycles per second.
`
`Hierarchy A set of transmission speeds arranged to
`multiplex signals at successively higher data rates.
`
`Hybrid Fiber/Coax A network that uses fiber to
`distribute cable-television signals to nodes, which in
`turn distribute them to homes over coaxial cable.
`
`Index-Matching Gel A gel or fluid with refractive
`index close to that of glass, which reduces refractive-
`index discontinuities that can cause reflective losses.
`
`Index of Refraction A quantity that measures how
`much the speed of light slows down in a material.
`Designated n, it is the speed of light in a vacuum
`divided by the speed of light in the material. Also
`called refractive index.
`
`

`

`Glossary
`
`Indium Gallium Arsenide (InGaAs) A semicon-
`ductor material used in lasers, LEDs, and detectors.
`
`out its two ports. The best-known type is a Mach-
`Zehnder interferometer.
`
`Indium Gallium Arsenide Phosphide (InGaAsP)
`A semiconductor material used in lasers, LEDs, and
`detectors.
`
`Standard packet-switched
`Internet Protocol (IP)
`transmission format for the Internet; uses variable-
`length packets.
`
`Infrared Light with wavelengths longer than 700 nm
`and shorter than about 1 mm, invisible to the human
`eye, which we can feel as heat. Glass optical fibers
`transmit infrared signals at 700 to about 1650 nm in
`the infrared.
`
`Infrared Fiber Colloquially, optical fiber with best
`transmission at wavelengths of 2 pm or longer, made
`of materials other than silica glass.
`
`Injection Laser Another name for a semiconductor
`or diode laser.
`
`Integrated Optics Optical devices that perform
`two or more functions and are integrated on a single
`substrate; analogous to integrated electronic circuits.
`
`Integrated Services D ig ita l N etw ork (ISD N )
`Originally a standard to transmit two digital voice
`lines at 64 kbit/s and one 16-kbit/s data channel.
`Now repackaged as IDSL, a form of DSL, transmit-
`ting 128 kbit/s over distances beyond the reach
`of DSL.
`
`Intensity Power per unit solid angle.
`
`Interference For light, the way that waves add
`together, depending on their phase. Constructive
`interference occurs when the waves are in phase and
`their amplitudes add. Destructive interference occurs
`when the waves are 180° out of phase and their
`amplitudes cancel.
`
`Interference Filter An optical filter that selectively
`transmits one wavelength and reflects others based on
`interference effects inside the structure. Also called
`dielectric filter.
`
`Interferometric Sensor A fiber-optic sensor that
`relies on interference effects.
`
`Interleaver An optical device that separates a series
`of optical channels so alternating wavelengths emerge
`
`Intrinsic Layer A layer of semiconductor that is
`not doped with impurities to form current carriers.
`
`Intrinsic Losses Splice losses arising from differ-
`ences in the fibers being spliced.
`
`Irradiance Power per unit area.
`
`Junction Laser A semiconductor diode laser.
`
`Junction Layer The layer between p - and «-doped
`semiconductors, where current carriers recombine
`and emit light in a semiconductor laser or LED.
`
`LAN See Local-Area Network.
`
`Large-Core Fiber Usually, a fiber with a core of
`200 (jtm or more.
`
`From light am p lification by stim u lated
`Laser
`emission o f radiation, one of the wide range of devices
`that generates light by that principle. Laser light is
`directional, covers a narrow range of wavelengths, and
`is more coherent than ordinary light. Semiconductor
`diode lasers are the usual light sources in fiber-optic
`systems.
`
`Layer A standard or protocol for signal transmis-
`sion or processing to perform certain functions. It
`includes standard interfaces with other layers, which
`perform other functions.
`
`L-Band Wavelengths of 1565 to 1625 nm where
`some erbium-doped fiber amplifiers operate. Separate
`from the C-band.
`
`LED See Light-Emitting Diode.
`
`Legacy Older equipment, generally no longer
`made.
`
`Light Strictly speaking, electromagnetic radiation
`visible to the human eye at 4 00 to 7 00 nm.
`Commonly, the term is applied to electromagnetic
`radiation with properties similar to visible light,
`
`

`

`Glossary
`
`including the invisible near-infrared radiation in
`most fiber-optic communication systems.
`
`Margin Allowance for attenuation in addition to
`that explicitly accounted for in system design.
`
`Light-Emitting Diode (LED) A semiconductor
`diode that emits incoherent light at the junction
`between p - and »-doped materials.
`
`Material Dispersion Pulse dispersion caused by
`variation of a material’s refractive index with wave-
`length.
`
`Lightguide An optical fiber or fiber bundle.
`
`Mbit/s Megabits (million bits) per second.
`
`Light Piping Use of optical fibers to illuminate.
`
`Lightwave An an adjective, a synonym for optical,
`often (but not always) meaning fiber-optic.
`
`Linewidth The range of wavelengths in an optical
`signal, sometimes called spectral width.
`
`Local-Area Network (LAN) A network that trans-
`mits data among many nodes in a small area (e.g., a
`building or campus).
`
`Local Loop The part of the telephone network
`extending from the central (switching) office to the
`subscriber.
`
`Longitudinal Modes Oscillation modes of a laser
`along the length of its cavity. Each longitudinal mode
`contains only a narrow range of wavelengths, so a
`laser emitting a single longitudinal mode has a nar-
`row bandwidth. Distinct from transverse modes.
`
`Loose Tube A protective tube loosely surrounding
`a cabled fiber, often filled with gel.
`
`Loss Attenuation of optical signal, normally meas-
`ured in decibels.
`
`Loss Budget An accounting of overall attenuation
`in a system.
`
`Mach-Zehnder Interferometer An optical device
`that separates a series of optical channels so alternat-
`ing wavelengths emerge out its two ports, sometimes
`called an interleaver.
`
`M AN (Metropolitan-Area Network) A network
`linking local-area networks, usually within a metro-
`politan area. MANs normally are private networks
`that serve one company’s facilities; metro networks
`are public networks run by companies that offer
`telecommunication services.
`
`Mechanical Splice A splice in which fibers are
`joined mechanically (e.g., glued or crimped in place)
`but not fused together.
`
`M E M S (M icro -electro-m ech an ical system s)
`Tiny moving elements, often mirrors, fabricated
`from semiconductor materials.
`
`Mesh A network that makes multiple interconnec-
`tions between different points.
`
`Metro Network A telecommunication system of-
`fering services to a metropolitan area, typically with
`cable lengths to 200 km.
`
`M icrobending Tiny bends in a fiber that allow
`light to leak out and increase loss.
`
`Micrometer One-millionth of a meter, abbrevi-
`ated |xm.
`
`Micron Short for the preferred form, micrometer.
`
`Modal Dispersion Dispersion arising from differ-
`ences in the times that different modes take to travel
`through multimode fiber.
`
`Mode An electromagnetic field distribution that
`satisfies theoretical requirements for propagation in a
`waveguide or oscillation in a cavity (e.g., a laser).
`Light has modes in a fiber or laser.
`
`Mode-Field Diameter The diameter of the one
`mode of light propagating in a single-mode fiber,
`slightly larger than core diameter.
`
`Mode Stripper A device that removes high-order
`modes in a multimode fiber to give standard mea-
`surement conditions.
`
`Modulation Changing the properties of a carrier
`wave so it transmits a signal. Amplitude modulation
`varies the wave amplitude.
`
`

`

`Multimode Transmits or emits multiple modes of
`light.
`
`Multiple System Operators (MSOs) Companies
`that operate cable television networks in many com-
`munities.
`
`Multiplexer A device that combines two or more
`signals into a single output.
`
`n Region A semiconductor doped to have an ex-
`cess of electrons as current carriers.
`
`N A See Numerical Aperture.
`
`Nanometer A unit of length, 10 9 m. It is part of
`the SI system and has largely replaced the non-SI
`Angstrom (0.1 nm) in technical literature.
`
`Near-Infrared The part of the infrared near the
`visible spectrum, typically 700 to 1500 or 2000 nm;
`it is not rigidly defined.
`
`Network A system of cables or other connections
`that links many terminals or devices, all of which can
`communicate with each other through the system.
`
`Noise Equivalent Power (NEP) The optical input
`power to a detector needed to generate an electrical
`signal equal to the inherent electrical noise.
`
`Interactions that are not propor-
`Nonlinear Effects
`tional to the strength of one light signal. For example,
`certain interactions are proportional to the square of
`the light power rather than to the power itself.
`Nonlinear effects can distort signals.
`
`Nonzero Dispersion-Shifted Fiber Single-mode
`optical fiber with the wavelength of zero chromatic
`dispersion shifted outside the C-band. Some types
`have zero dispersion near 1500 nm, others near
`1625 nm. Types with zero dispersion at 1580 nm are
`not usable in the L-band of erbium-doped fiber
`amplifiers.
`
`No Return to Zero (NRZ) A digital code in
`which the signal level is low for a 0 bit and high for
`a 1 bit and does not return to 0 between successive
`1 bits.
`
`Normal (angle) Perpendicular to a surface.
`
`Glossary
`
`N TSC The analog video broadcast standard used
`in North America, set by the National Television
`System Committee.
`
`Numerical Aperture (NA) The sine of half the
`angle over which a fiber can accept light. Strictly
`speaking, this is multiplied by the refractive index of
`the medium containing the light, but for air the
`index is almost equal to 1.
`
`O-Band Wavelengths of 1270 to 1370 nm, the
`“original” band for fiber transmission.
`
`O C -x Optical Carrier, a carrier rate specified in the
`SONET standard.
`
`Optical Add-Drop An optical multiplexer that drops
`and/or adds one or more optical channels to a signal.
`
`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.
`
`Optical Channel An optical signal transmitted at
`one wavelength. W DM systems transmit multiple
`channels at separate wavelengths.
`
`Optical Circulator A device that transmits light
`only in one direction through a series of ports, so light
`can go from port 1 to port 2 and port 2 to port 3, but
`not from port 2 to port 1.
`
`Optical Isolator A device that transmits light in one
`direction but blocks light in the opposite direction.
`
`O ptical Networking Processing and switching
`signals in optical form as well as transmitting them
`optically.
`
`Optical Node The point where signals are trans-
`ferred from optical fibers to other transmission media,
`typically twisted-pair wires or coaxial cable.
`
`Optical Performance Monitor A device installed
`in a W DM system to monitor signals at the trans-
`mitted wavelengths.
`
`Optical Spectrum Analyzer An instrument that
`scans the spectrum to record power as a function of
`wavelength.
`
`

`

`m Glossary
`
`Optical Loss Test Set An optical power meter and
`light source calibrated for use together.
`
`Photons Quanta of electromagnetic radiation. Light
`can be viewed as either a wave or a series of photons.
`
`Optical Switch A switch that operates on light,
`redirecting optical signals.
`
`Optical Tim e-Dom ain Reflectometer (O TD R)
`An instrument that measures transmission character-
`istics by sending a short pulse of light down a fiber
`and observing backscattered light.
`
`Optical Waveguide Technically, any structure that
`can guide light. Sometimes used as a synonym for
`optical fiber, it can also apply to planar light wave-
`guides.
`p Region Part of a semiconductor doped with elec-
`tron acceptors in which holes (vacancies in the valence
`electron level) are the dominant current carriers.
`
`Packet Switching Organizing signals by dividing
`them into data packets, each containing a header that
`specifies its destination and data intended for that
`destination. Separate data packets then are directed
`to their destinations.
`
`Passive Component A component that doesn’t
`require outside power.
`
`Passive Optical Network A fiber-optic distribu-
`tion network with no active components between the
`switching office and the customer.
`
`PCS Fiber See Plastic-Clad Silica Fiber.
`
`Peak Power Highest instantaneous power level in
`a pulse.
`
`Phase The position of a wave in its oscillation cycle.
`
`Photodetector A light detector.
`
`Photodiode A diode that can produce an electrical
`signal proportional to light falling upon it.
`
`Photonic A term coined for devices that work using
`photons or light, analogous to “electronic” for devices
`working with electrons.
`
`Photonic Bandgap A range of wavelengths that
`cannot propagate in materials with certain internal
`microstructures.
`
`Picosecond One-trillionth (10 12) second.
`pin Photodiode A semiconductor detector with an
`intrinsic (z) region separating the p - and «-doped
`regions. It has fast linear response and is used in fiber-
`optic receivers.
`
`Planar Waveguide A flat waveguide formed on the
`surface of a flat material. The zone of high refractive
`index is rectangular in cross-section and guides light
`in the same way as the core of an optical fiber.
`
`Plastic-Clad Silica (PCS) Fiber A step-index mul-
`timode fiber in which a silica core is surrounded by a
`lower-index plastic cladding.
`
`Plastic Fiber An optical fiber made entirely of
`plastic compounds.
`
`Plenum Cable Cable made of fire-retardant mate-
`rial that meets electrical code requirements (UL 910)
`for low smoke generation and installation in air spaces.
`
`Plesiochronous D igital Hiera