FOA CFOS/C key terms

A thin strand of glass or plastic that carries information as pulses of light confined to a core by a surrounding cladding of lower refractive index. It is the transmission medium in fiber optic networks.

The central light-guiding region of an optical fiber, made of doped silica with a higher refractive index than the cladding. Its diameter, typically 9 µm single-mode or 50/62.5 µm multimode, sets the fiber's transmission characteristics.

The glass layer surrounding the fiber core with a slightly lower refractive index. It reflects escaping light back into the core and provides mechanical protection for the light-guiding boundary.

The optical effect in which light striking the core-cladding boundary above the critical angle is reflected back into the core instead of refracting out. It is the mechanism that keeps light guided along the fiber.

A dimensionless number describing the range of angles over which a fiber accepts incoming light. Higher NA means a wider acceptance cone and more light coupled in, typical of multimode fiber.

Fiber with a small core, about 8 to 10 µm, that propagates only one light path at the operating wavelength. It supports long distances and high bandwidth and is standard for outside plant and campus backbones.

Fiber with a larger core, usually 50 or 62.5 µm, that carries many light paths simultaneously. It is used for shorter building and data center links because modal dispersion limits distance and bandwidth.

Pulse spreading caused by different light paths in a multimode fiber arriving at slightly different times. It limits the bandwidth-distance product and is the main reason multimode links are restricted in length.

The loss of optical power as light travels through fiber, connectors, and splices, measured in decibels. It results from absorption, scattering, and bending and sets the maximum usable link length.

The distance between successive peaks of a light wave, usually expressed in nanometers for fiber optics. Common operating windows are 850, 1300, 1310, and 1550 nm, each with different loss and dispersion behavior.

A logarithmic unit expressing the ratio of two power levels. In fiber optics it describes loss or gain, and a 3 dB change corresponds to a doubling or halving of optical power.

The active device, typically an LED or laser diode, that converts an electrical signal into modulated light launched into the fiber. Its output power and wavelength must match the receiver and fiber type.

The active device containing a photodiode that converts incoming light back into an electrical signal. It has a sensitivity threshold and a maximum input power beyond which it saturates or is damaged.

Fiber optic cable, hardware, and enclosures installed outdoors between buildings, along poles, or underground. OSP work involves aerial, direct-buried, and conduit installations exposed to weather and environmental hazards.

Structured cabling installed inside a building or campus, including horizontal, backbone, and work area cabling. It follows standardized topologies and is documented for administration and future moves.

The cabling that connects telecommunications rooms, equipment rooms, and building entrances, carrying traffic between floors or buildings. It is typically high-fiber-count cable designed for longer runs and higher capacity.

The cabling that runs from a telecommunications room to individual work area outlets on the same floor. It is usually limited in length and installed in a star topology for easy administration.

A dedicated space housing cross-connects, patch panels, and active equipment that serves a defined area of a building. It is the distribution point where horizontal cabling terminates and backbone cabling connects.

A rack-mounted panel where incoming cables terminate on the rear and are connected to equipment via patch cords on the front. It provides organized, labeled administration of a cabling system.

A short, flexible cable with connectors on both ends used to link patch panel ports to active equipment or outlets. Its connector types and polish must match the ports it joins.

A field-installable or factory-terminated device at the end of a fiber that allows repeated mating with another connector. Common styles include SC, LC, and ST, each with defined ferrule and latch designs.

The precision cylindrical tube, usually ceramic, that holds and centers the fiber in a connector. Its bore and endface geometry determine alignment quality and mating loss.

The endface geometry of a connector ferrule, such as PC, UPC, or APC. APC uses an angled, typically 8-degree, contact surface to reduce back reflection, while UPC is flat and polished.

A permanent joint between two fibers made by fusion welding or mechanical alignment. Splices have lower loss than connectors and are used where a connection will not need to be changed.

A field instrument that aligns two prepared fiber ends and fuses them with an electric arc. It estimates splice loss and is used to build continuous cable runs with minimal attenuation.

The process of scoring and breaking a fiber to produce a flat, perpendicular endface before splicing or connector termination. A poor cleave causes high splice loss or failed terminations.

The reduction in optical power caused by inserting a component such as a connector, splice, or splitter into a link, expressed in decibels. It is a key input to the loss budget calculation.

Light reflected back toward the source at a connector or splice interface, also called return loss when expressed as a positive dB value. High back reflection can destabilize lasers and degrade link performance.

The calculated maximum allowable optical loss for a link, derived from transmitter output, receiver sensitivity, and safety margin. It is compared against estimated or measured loss to confirm the design will work.

A test instrument that launches light pulses into a fiber and analyzes backscattered light to locate events and measure loss versus distance. It is used for acceptance testing and fault location on installed links.

A paired light source and power meter used to measure end-to-end insertion loss of a fiber link at a specified wavelength. Results are compared with the loss budget to accept or reject the installation.

Visual examination of a connector or ferrule endface with a microscope or automated analyzer to detect dirt, scratches, and defects before mating. It is a mandatory step in a proper cleaning and testing process.

Removal of dust, oil, and residue from connector endfaces and mating adapters using approved wipes, solvents, and tools. Contamination is a leading cause of high loss and permanent connector damage.

The minimum radius to which a cable or fiber may be bent without damage or excess loss. Violating it causes macrobending loss and can crack fibers, so manufacturers publish limits for installation and routing.

A bend in a fiber with a radius large enough to be visible, which allows light to escape the core and increases attenuation. It is commonly caused by poor cable routing or tight tie-wraps.

The longitudinal force applied to a cable during installation, which must stay below the manufacturer's limit. Excess tension stretches or breaks fibers and is a common cause of latent installation failure.

A compatible compound applied to cable or conduit to reduce friction during installation. It helps keep pulling tension within limits and must not degrade the cable jacket or fill compounds.

A tube or duct, made of metal, plastic, or fiber, that routes and protects cable. Fill ratios and bend limits must be respected so cable can be pulled without damage.

Stringing fiber cable on poles using strand, lashers, or ADSS cable designed to support its own weight. It requires attention to sag, clearance, and wind and ice loading.

Cable designed for placement in a trench without conduit, using armored or heavy-jacketed constructions. It must tolerate soil pressure, moisture, and rodent activity.

A plan that sequences installation tasks, durations, dependencies, and milestones so the fiber project completes on time. It drives crew assignments, material deliveries, and testing windows.

An itemized list of all components, quantities, and part numbers needed for a fiber project, including cable, connectors, hardware, and test equipment. It supports procurement and cost estimating.

A pre-installation walkthrough that documents pathways, spaces, distances, hazards, and access constraints. Its findings inform the design, cost estimate, and installation plan.