FOA CFOT key terms

A thin strand of glass or plastic that carries information as pulses of light. It consists of a core that guides the light and a cladding that keeps the light inside the core.

The central, light-carrying region of an optical fiber. Its diameter and refractive index profile determine how many modes the fiber supports and how the light propagates.

The layer of glass surrounding the fiber core that has a lower refractive index than the core. It confines light to the core through total internal reflection and provides mechanical protection.

The optical effect in which light traveling in a higher-index medium strikes a boundary with a lower-index medium at a shallow angle and is reflected back rather than passing through. This effect guides light along the fiber core.

A measure of the range of angles over which a fiber can accept incoming light. A larger numerical aperture means the fiber accepts light from a wider cone and typically supports more modes.

An optical fiber with a very small core that supports only one propagation path for light. It is used for long-distance and high-bandwidth transmission because it avoids modal dispersion.

An optical fiber with a larger core that allows multiple light paths, or modes, to travel simultaneously. It is commonly used for shorter-distance premises and data center links.

The diameter of the light-carrying area in a single-mode fiber, measured where the optical power falls to a specified fraction of its peak. It affects splice loss and connector performance.

The loss of optical power as light travels through a fiber, caused by absorption and scattering. It is usually expressed in decibels per kilometer and limits the distance a signal can travel.

The spreading of light pulses as they travel through a fiber, which can cause adjacent pulses to overlap and corrupt data. It results from different path lengths or different wavelengths traveling at different speeds.

The distance between successive peaks of a light wave, commonly measured in nanometers. Fiber optic systems use specific wavelengths, such as 850, 1300, and 1550 nm, chosen for low loss or low dispersion.

A logarithmic unit used to express the ratio of two power levels. In fiber optics it is used to describe loss and gain, such as attenuation in dB per kilometer or connector loss in dB.

A removable device terminated on the end of a fiber that allows quick connection and disconnection to another fiber or to equipment. Common styles include SC, LC, and ST.

A precision cylindrical tube, usually ceramic, that holds the bare fiber in an optical connector and aligns it with the mating connector. Its hole size and concentricity are critical to low-loss connections.

The shape and finish of the endface of a fiber connector ferrule, such as flat, physical contact, or angled physical contact. The geometry controls how two connectors mate and how much light is reflected back.

A connector endface design in which the fiber surfaces are domed and pressed together when mated, eliminating an air gap. This reduces insertion loss and back reflection compared with flat polished connectors.

A measure of the amount of light reflected back toward the source at a connector or splice, expressed in decibels. Higher return loss values indicate less reflection and better performance.

The reduction in optical power caused by inserting a component, such as a connector or splice, into a fiber link. It is measured in decibels and is a key part of the link loss budget.

A permanent joint made by melting the ends of two fibers together with an electric arc. A well-made fusion splice has very low loss and high mechanical strength.

A permanent or semi-permanent joint that aligns and holds two fiber ends together with a mechanical fixture, often using an index-matching gel. It is simpler than fusion splicing but usually has higher loss.

A rack-mounted or wall-mounted enclosure that holds fiber adapters and provides a convenient point to cross-connect or interconnect fiber cables. It protects splices and organizes cable management.

The fiber and copper cabling installed inside a building or campus, including backbone and horizontal cabling. It connects equipment rooms, telecommunications rooms, and work areas.

The main cable that connects telecommunications rooms, equipment rooms, or buildings within a campus. It typically carries high fiber counts and may be single-mode or multimode.

The cabling that runs from a telecommunications room to individual work areas, such as outlets in offices. It is usually limited in length and may use multimode fiber or copper.

Fiber optic cables and associated hardware installed outdoors, such as aerial, buried, or underground routes between buildings or to homes. OSP cables are designed to withstand weather, moisture, and physical stress.

A fiber optic cable designed to be installed on poles or suspended between structures. It often includes a strength member and may be lashed to a messenger wire or self-supporting.

A fiber optic cable installed directly in the ground, usually in a trench or by plowing, and often protected by conduit or a warning tape. It must resist moisture, crushing, and rodent damage.

A tube or duct, often made of plastic or metal, that protects and routes cables underground or inside buildings. It allows cables to be pulled in and replaced later.

The process of installing cable by pulling it through conduit or ducts using a pull rope or tape. Care must be taken to avoid exceeding the cable's tensile strength and bend radius.

The minimum radius to which a fiber cable or fiber can be bent without causing damage or increased loss. Violating the bend radius can break fibers or cause bending loss.

The maximum amount of optical loss that a fiber link can tolerate while still operating reliably. It is calculated from transmitter power, receiver sensitivity, and allowances for connectors, splices, and fiber attenuation.

A complete optical path between a transmitter and a receiver, including fiber cable, connectors, splices, and passive components. Its performance is verified by testing loss and length.

A technique that combines multiple optical signals at different wavelengths onto a single fiber to increase capacity. Each wavelength carries an independent data channel.

A test instrument that sends light pulses into a fiber and analyzes the reflected light to measure loss, locate faults, and measure distance. It provides a trace of loss versus distance along the fiber.

A pair of instruments, a light source and an optical power meter, used to measure the total insertion loss of a fiber link. It is the standard tool for tier 1 link certification.

An instrument that measures the optical power of a light signal, usually in decibels relative to a milliwatt or in microwatts. It is used with a light source to test link loss.

A standardized procedure for setting the reference or zero point on an optical loss test set before measuring a link. It ensures that connector and launch conditions are consistent and measurements are comparable.

A broadband network architecture in which optical fiber is run all the way to individual residences. It supports high-speed internet, television, and telephone services over a single fiber.

A point-to-multipoint fiber network that uses unpowered optical splitters to share a single feeder fiber among multiple subscribers. It is widely used for fiber-to-the-home deployments.

A passive device that divides an incoming optical signal into multiple output fibers, typically in ratios such as 1:8 or 1:32. It is a key component of passive optical networks.

The equipment at the service provider's central office or headend that manages and terminates the passive optical network. It sends and receives signals to and from subscriber optical network terminals.

The device at the subscriber's premises that converts optical signals from the fiber network into electrical signals for customer equipment. It is the endpoint of a fiber-to-the-home connection.