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To navigate the complex world of fiber optics effectively, it's essential to understand the terminology associated with this technology. In this comprehensive glossary, we'll break down the key terms into specific categories for a better understanding.
Metric System:
Fiber optics, as a universal technology, relies on the metric system for measurement standards. Familiarize yourself with these essential metrics:
Meter: Equivalent to 3.28 feet (or more precisely, 3.28084 feet).
Kilometer: Corresponds to 1000 meters, 3,281 feet, or 0.62 miles.
Micron: Represents 1/1,000,000th of a meter. In the fiber optics industry, it is a common unit of measurement for fibers.
Nanometer: One billionth of a meter, typically used in the fiber optics industry to express the wavelength or frequency of transmitted light.
Watts: A linear measure of optical power, usually expressed in milliwatts (mW), microwatts (*W) or nanowatts (nW).
Before diving into any hands on terminology, it's crucial to understand the fundamental components of fiber optics:
Fiber optics (fo): Light transmission through flexible transmissive fibers for communications or lighting.
Optical Fiber: Thin strands of highly transparent glass or plastic designed to guide light.
Core: The central part of the fiber where light transmission occurs.
Cladding: The outer optical layer that traps and guides light within the core, even through curves.
Buffer Coating or Primary Coating: A protective hard plastic layer on the outer surface of the fiber, guarding against moisture and physical damage.
Mode: A single electromagnetic field pattern (akin to a ray of light) that travels within the fiber.
Multimode Fiber: Featuring a larger core (62.5 or 50 microns) and employed with LED sources for short-distance, lower-speed networks, such as LANs.
Singlemode Fiber: With a much smaller core, about 9 microns, networks, telephony, and CATV with laser sources for long-distance, high-speed applications.
Network: A system of cables, hardware and equipment used for communications.
Jumper cable: A short single fiber cable with connectors on both ends used for interconnecting other cables or testing.
Plastic Optical Fiber (POF): A multimode fiber with a large core (about 1mm) utilized in short, low-speed networks. POF has gained popularity in consumer HiFi and car communication systems.
Graded-Index Fiber: A multimode fiber with a core that has a lower refractive index in the center than at the edges.
Singlemode Fiber: A fiber that supports only one mode.
Edge-Emitting Diode (E-LED): A LED that emits from the edge of the semiconductor chip, producing higher power and narrower spectral width.
Helium-Neon Laser: A type of gas laser that emits a red light beam.
Laser: Light Amplification by Stimulated Emission of Radiation.
Light Emitting Diode (LED): A semiconductor that emits light when current flows through it.
Light Source: The device that provides the light for a fiber optic system.
S/N Ratio: Signal-to-Noise ratio.
Signal: Information-carrying electromagnetic or optical wave.
Faraday Rotation: The rotation of the plane of polarized light in a magnetic field.
Polarization: The orientation of electromagnetic wave vibrations.
Decibels (dB): A unit of measurement of optical power which indicates relative power. A -10 dB means a reduction in power by 10 times, -20 dB means another 10 times or 10 times overall, -30 means another 10 times or 1000 times overall and so on.
dB: Optical power referenced an arbitrary zero level
dBm: Optical power referenced to 1 milliwatt
Optical Loss: The amount of optical power lost as light is transmitted through fiber, splices, couplers, etc, expressed in dB.
Optical Power: is measured in "dBm", or decibels referenced to one miliwatt of power. While loss is a relative reading, optical power is an absolute measurement, referenced to standards. You measure absolute power to test transmitters or receivers and relative power to test loss.
Scattering: The change of direction of light after striking small particles that causes loss in optical fibers and is used to make measurements by an OTDR
Wavelength: A term for the color of light, usually expressed in nanometers (nm) or microns (m). Fiber is mostly used in the infrared region where the light is invisible to the human eye.
Wavelength division multiplexing (WDM): A technique of sending signals of several different wavelengths of light into the fiber simultaneously.
Total internal reflection: Confinement of light into the core of a fiber by the reflection off the core-cladding boundary.
PON (Passive Optical Network): A Passive Optical Network (PON) is a type of telecommunications network that uses fiber-optic cables to distribute signals. Unlike active optical networks, PONs do not require powered equipment for signal transmission, making them more cost-effective and efficient.
GPON (Gigabit Passive Optical Network): GPON (Gigabit Passive Optical Network) is an advanced version of PON that provides high-speed internet access, voice, and video services over a single fiber-optic connection. It offers faster data transmission and is widely used in modern broadband networks.
OLT (Optical Line Terminal): The Optical Line Terminal (OLT) is a key component in a PON network. It connects the optical fiber network to the broader internet or service provider network and manages the data traffic between the service provider and the customer's premises.
ONT (Optical Network Terminal): An Optical Network Terminal (ONT) is the customer-side equipment in a PON network. It is responsible for converting optical signals into electrical signals that can be used by customer devices such as routers and computers.
ONU (Optical Network Unit): An Optical Network Unit (ONU) is essentially the same as an ONT and is used interchangeably in many cases. It serves as the endpoint device at the customer's location, connecting to the OLT through the PON infrastructure to access internet and other services.
To understand fiber optic cabling, consider the following terms:
Cable: Fiber requires protection when installed, and cables serve this purpose. They can contain anywhere from one to hundreds of fibers.
Jacket: The durable outer covering of the cable, which must meet fire codes for indoor installations.
Strength Members: Aramid fibers (such as Kevlar) used to help protect and can be used to pull the cable, or fiberglass rods to prevent kinking.
Armor: Typically of metallic nature located underneath the cable jacket designed to deter rodents from chewing through the cable and to provide crush resistance.
Fiber optics, as a universal technology, relies on the metric system for measurement standards. Familiarize yourself with these essential metrics:
Attenuation: The reduction in optical power as it travels along a fiber, usually expressed in decibels (dB).
Attenuation Coefficient: A characteristic of the attenuation of an optical fiber per unit length, expressed in dB/km.
Chromatic Dispersion: The temporal spreading of a pulse in an optical waveguide caused by the wavelength dependence of the velocities of light.
Cladding: The lower refractive index optical coating over the core of the fiber that "traps" light into the core.
Core: The center of the optical fiber through which light is transmitted.
Cutoff Wavelength: The wavelength beyond which singlemode fiber only supports one mode of propagation.
Dispersion: The temporal spreading of a pulse in an optical waveguide, which may be caused by modal or chromatic effects.
Excess Loss: The amount of light lost in a coupler, beyond that inherent in the splitting ratio, caused by reflections and absorption.
Index of Refraction (IOR): A measurement of the speed of light in a particular medium.
Mode Field Diameter: A measure of the size of the guided lightwave in the core of the fiber.
Numerical Aperture (NA): A measurement of the range of angles over which the fiber can accept or emit light.
Refractive Index: A measure of how much a ray of light is bent when it enters a material.
Velocity of Light: The speed of light in a vacuum, approximately 3 x 10^8 meters per second.
Wavelength: The distance between two peaks of an electromagnetic wave.
Cable Plant, Fiber Optic: The combination of fiber optic cable sections, connectors, and splices forming the optical path between two terminal devices.
Connector: A device that provides for a demountable connection between two fibers or a fiber and an active device and provides protection for the fiber.
Coupler: An optical device that splits or combines light from more than one fiber.
End Finish: The quality of the end surface of a fiber prepared for splicing or terminated in a connector.
Ferrule: A precision tube used to align two fibers for connection.
Fiber Optic Panel (FOP): A panel for managing and interconnecting fiber optic systems.
Fiber Optic Repeater: A device that amplifies and retransmits digital signals using lightwave technology.
Fiber Pigtail: A short optical fiber permanently attached to a light source or detector.
Jumper: A short length of fiber connecting two devices.
Termination is a critical aspect of fiber optics. It involves preparing the end of a fiber for connection. Explore the following terms:
Connector: A non-permanent device for connecting two fibers or fibers to equipment. It offers protection and is suitable for occasional disconnection, testing, or rerouting.
Ferrule: A tube holding a fiber for alignment, often a component of a connector.
Splice: A permanent connection between two fibers.
Mechanical Splice: A splice created through mechanical alignment.
Fusion Splice: Achieved by welding or fusing two fibers.
Fusion Splicer: An instrument for splicing fibers via electrical arc.
Hardware: Terminations and splices require additional hardware for protection and management, such as patch panels and splice closures.
Jacket Slitter or Stripper:A cutter for removing the heavy outside jacket of cables
Fiber Stripper: A precise stripper used to remove the buffer coating of the fiber itself for termination. There are three types in common use, called by their trade names: "Miller Stripper", "No-Nik" and "Micro Strip."
Cleaver: A tool that precisely "breaks/cuts" the fiber to produce a flat end for polishing or splicing.
Scribe: A hard, sharp tool that scratches the fiber to allow cleaving.
Polishing Puck: for connectors that require polishing, the puck holds the connector in proper alignment to the polishing film.
Polishing Film: Fine grit film used to polish the end of the connector ferrule.
Crimper: A tool that crimps the connector to the aramid fibers in the cable to add mechanical strength.
Attenuator: A device that reduces signal power in a fiber optic link by inducing loss.
Average Power: The average over time of a modulated signal.
Back Reflection, Optical Return Loss: Light reflected from the cleaved or polished end of a fiber caused by the difference in refractive indices of air and glass. Typically, it accounts for about 4% of the incident light, expressed in dB relative to incident power.
Backscattering: The scattering of light in a fiber back toward the source, used to make OTDR measurements.
Bending Loss, Microbending Loss: Loss in fiber caused by stress on the fiber bent around a restrictive radius.
Excess Loss: The amount of light lost in a coupler, beyond that inherent in the splitting ratio, caused by reflections and absorption.
Fusion Splice Loss: The loss of a fusion splice in a fiber optic cable.
Insertion Loss: The loss of power resulting from the insertion of a device in a transmission line.
Splice Loss: The loss of power resulting from the fusion of two fibers.
Cutback Method: A technique for measuring the loss of bare fiber by measuring the optical power transmitted through a long length, then cutting back to the source and measuring the initial coupled power.
Optical Loss Test Set (OLTS): A test set used to measure the total optical power transmitted through a fiber optic cable.
Optical Power Meter: A test instrument used to measure optical power.
Optical Spectrum: A range of optical wavelengths.
Optical Time Domain Reflectometer (OTDR): A test instrument used to characterize an optical fiber.
Spectrum Analyzer: An instrument that displays the signal levels of a fiber.
Optical Power Meter: An instrument that measures optical power from the end of a fiber
Test Source: an instrument that uses a laser or LED to send an optical signal into fiber for testing loss of the fiber
Optical Loss Test Set (OLTS): A measurement instrument for optical loss that includes both a meter and source
Reference Test Cables: short, single fiber cables with connectors on both ends, used to test unknown cables.
Mating Adapter: also called splice bushing or couplers, allow two cables with connectors to mate.
Fiber Tracer: An instrument that allows visual checking of continuity and tracing for correct connections
Visual Fault Locator: A device that allows visual tracing and testing of continuity by illuminating a particular strand of fiber with a laser.
Microscope: used to inspect the endface or surface of a connector for flaws or dirt.
Bit-Error Rate (BER): The fraction of data bits transmitted that are received in error.
Bit: An electrical or optical pulse that carries information.
Digital: Signals encoded into discrete bits.
Modulation: The encoding of digital information onto a carrier wave.
Transceiver: A transmitter/receiver.
Transmitter: The part of a fiber optic link that converts electrical signals into optical signals.
LAN (Local Area Network): A Local Area Network (LAN) is a network that covers a relatively small geographic area, such as a single building or a campus. LANs are used for connecting computers, devices, and resources within the same physical location, enabling them to communicate and share information.
WAN (Wide Area Network): A Wide Area Network (WAN) is a network that spans a larger geographic area, often connecting multiple LANs or individual devices over long distances. WANs facilitate data transmission between different locations and can use various technologies, including public and private networks.
POE (Power over Ethernet): Power over Ethernet (PoE) is a technology that allows electrical power and data to be transmitted over an Ethernet network cable simultaneously. PoE is often used to power devices like IP cameras, phones, and wireless access points (WAPs) via the network cable.
CATV: An abbreviation for Community Antenna Television or cable TV.
ESCON: IBM standard for connecting peripherals to a computer over fiber optics. Acronym for Enterprise System Connection.
Fiber Optic Backlight: A light source used for displays, consisting of a flat slab of glass or plastic.
Fiber-to-the-Home (FTTH): The installation and use of optical fiber from a central point directly to individual buildings, such as residences and businesses.
Fiber-to-the-X (FTTX): encompasses a range of broadband optical fiber distribution configurations categorized according to the point at which the fiber optic line terminates and the transition to metallic network lines occurs.
Fiber-to-the-Antena (FTTA) utilized when fiber network lines extend to radio antennas equipped with optical transceivers and transmitters for the conversion of optical signals into radio waves. FTTA networks form the fundamental infrastructure for 3G, 4G, and 5G mobile networks.
Fibre Channel: A set of American National Standards Institute (ANSI) standards for data transmission.
Fibre Channel Protocol (FCP): A protocol for accessing and managing data on a Fibre Channel network.
Link Loss Budget: The total allowable loss for a fiber optic link, considering all components.
Router: A device that forwards data packets between computer networks.
Time Division Multiplexing (TDM): A method for putting multiple signals on a single transmission line.
TIA Codes: A set of standards and guidelines established by the Telecommunications Industry Association (TIA) that govern various aspects of the telecommunications industry, including cabling standards, infrastructure design, and performance specifications.
606: TIA-606 is a specific standard within the TIA codes that provides guidelines for the administration and labeling of telecommunications cabling and infrastructure within a facility. It helps ensure that cabling systems are organized and well-documented.
568: TIA-568 is another standard within the TIA codes that specifies the design and performance requirements for structured cabling systems, particularly those used in Ethernet networks. It covers aspects like cable categories, connectors, and wiring schemes.
EIA 569: EIA-569, now part of the TIA standards, provides guidelines for designing and constructing telecommunications pathways and spaces, including telecom rooms and pathways between them. It focuses on ensuring efficient cable management, organization, and physical infrastructure for telecommunications systems.
PON (Passive Optical Network): A Passive Optical Network (PON) is a fiber-optic telecommunications network architecture that uses point-to-multipoint topology to provide broadband access. PONs are typically used for delivering services like internet, voice, and video to subscribers. They are characterized by passive components and optical splitters that enable shared fiber connections.
Absorption: That portion of fiber optic attenuation resulting of conversion of optical power to heat.
Analog: Signals that are continually changing, as opposed to being digitally encoded.
Detector: A photodiode that converts optical signals to electrical signals.
EDFA: Erbium-doped fiber amplifier, an all optical amplifier for 1550 nm SM transmissionsystems.
Equilibrium modal distribution (EMD): Steady state modal distribution in multimode fiber, achieved some distance from the source, where the relative power in the modes becomes stable with increasing distance.
Fiber Amplifier: an all optical amplifier using erbium or other doped fibers and pump lasers to increase signal output power without electronic conversion.
Fiber Distributed Data Interface, FDDI: 100 Mb/s ring architecture data network. Ferrule: A precision tube which holds a fiber for alignment for interconnection or termination. A ferrule may be part of a connector or mechanical splice.
Fresnel reflection, back reflection, optical return loss: Light reflected from the cleaved or polished end of a fiber caused by the difference of refractive indices of air and glass.
Index matching fluid: A liquid used of refractive index similar to glass used to match the materials at the ends of two fibers to reduce loss and back reflection.
Launch cable: A known good fiber optic jumper cable attached to a source and calibrated for output power used used as a reference cable for loss testing. This cable must be made of fiber and connectors of a matching type to the cables to be tested.
Laser diode, ILD: A semiconductor device that emits high powered, coherent light when stimulated by an electrical current. Used in transmitters for singlemode fiber links.
Light-emitting diode, LED: A semiconductor device that emits light when stimulated by an electrical current. Used in transmitters for multimode fiber links.
Link, fiber optic: A combination of transmitter, receiver and fiber optic cable connecting them capable of transmitting data. May be analog or digital.
Long wavelength: A commonly used term for light in the 1300 and 1550 nm ranges.
Loss, optical: The amount of optical power lost as light is transmitted through fiber, splices, couplers, etc.
Margin: The additional amount of loss that can be tolerated in a link.
Modal dispersion: The temporal spreading of a pulse in an optical waveguide caused by modal effects.
Mode filter: A device that removes optical power in higher order modes in fiber.
Mode scrambler: A device that mixes optical power in fiber to achieve equal power distribution in all modes. Mode stripper: A device that removes light in the cladding of an optical fiber.
Optical amplifier: A device that amplifies light without converting it to an electrical signal.
Optical switch: A device that routes an optical signal from one or more input ports to one or more output ports. Optical time domain reflectometer (OTDR): An instruments that used backscattered light to find faults in optical fiber and infer loss.
Overfilled launch: A condition for launching light into the fiber where the incoming light has a spot size and NA larger than accepted by the fiber, filling all modes in the fiber.
Photodiode: A semiconductor that converts light to an electrical signal, used in fiber optic receivers.
Plastic-clad silica (PCS) fiber: A fiber made with a glass core and plastic cladding.
Power budget: The difference (in dB) between the transmitted optical power (in dBm) and the receiver sensitivity (in dBm).
Preform: The large diameter glass rod from which fiber is drawn.
Receive cable: A known good fiber optic jumper cable attached to a power meter used as a reference cable for loss testing. This cable must be made of fiber and connectors of a matching type to the cables to be tested.
Receiver: A device containing a photodiode and signal conditioning circuitry that converts light to an electrical signal in fiber optic links.
Short wavelength: A commonly used term for light in the 665, 790, and 850 nm ranges.
Splitting ratio: The distribution of power among the output fibers of a coupler.
Steady state modal distribution: Equilibrium modal distribution (EMD) in multimode fiber, achieved some distance from the source, where the relative power in the modes becomes stable with increasing distance. Step index fiber: A multimode fiber where the core is all the same index of refraction.
Surface emitter LED: A LED that emits light perpendicular to the semiconductor chip. Most LEDs used in datacommunications are surface emitters.
Talkset, fiber optic: A communication device that allows conversation over unused fibers.
Test kit: A kit of fiber optic instruments, typically including a power meter, source and test accessories used for measuring loss and power.
VCSEL: vertical cavity surface emitting laser, a type of laser that emits light vertically out of the chip, not out the edge.
Working margin: The difference (in dB) between the power budget and the loss budget (i.e. the excess power margin).
With this organized glossary, you can delve into the world of fiber optics with a clear understanding of its terminology and how it fits into various categories. Whether you're new to fiber optics or a seasoned professional, this glossary provides a valuable resource for effective communication and troubleshooting in the field.