FOA CFOT flashcards

33 cards. Read the term and the definition here. The deck at the top of this page is optional.

Critical angle

The minimum incidence angle at which light in the core is totally internally reflected at the cladding boundary; it depends on the refractive indices of core and cladding.

Numerical aperture

A measure of the range of angles over which a fiber accepts light; single-mode fiber has a small NA, multimode a larger one.

Modal dispersion

Pulse spreading in multimode fiber caused by different modes traveling different path lengths; graded-index profiles reduce it, and it is absent in single-mode fiber.

Chromatic dispersion

Pulse spreading because different wavelengths travel at slightly different speeds; it affects all fibers and is minimized near 1310 nm in standard single-mode fiber.

APC connector

An angled physical contact connector with an 8-degree polished endface, usually green, offering lower reflectance than UPC; it must never be mated to a UPC connector.

Fusion splice

A permanent joint made by electrically arcing two prepared fiber ends together; typical loss is about 0.05 to 0.1 dB.

WDM

Wavelength division multiplexing sends multiple signals on separate wavelengths over one fiber; CWDM uses wide spacing and DWDM tight spacing for high capacity.

Single-mode fiber

Fiber with an approximately 8 to 10 micrometer core and small numerical aperture that carries one mode, giving low loss and long reach at 1310 and 1550 nm.

Horizontal cabling limit

The permanent horizontal link is limited to 90 meters, with up to 10 meters of patch cords, for a 100-meter maximum channel length.

Plenum cable rating

OFNP cable is rated for air-handling spaces and has low smoke and flame spread; it is required in plenums instead of riser-rated OFNR cable.

Minimum bend radius

The smallest radius a cable may be bent without damage or loss; commonly 10 times the cable diameter during installation and per manufacturer spec after installation.

Entrance facility

The point where outside plant cable enters a building and transitions to indoor-rated cable, typically within 15 meters of the entry point.

OM3 and OM4

Laser-optimized multimode fiber grades, usually aqua-jacketed, supporting 10 Gigabit Ethernet to roughly 300 and 400 meters respectively.

Backbone cabling

Cabling that connects entrance facilities, equipment rooms, and telecommunications rooms; it usually uses higher fiber counts and includes spare strands.

ADSS cable

All-dielectric self-supporting cable used for aerial spans without a messenger strand; it carries its own mechanical load and resists electrical interference.

Loose-tube cable

Outside plant cable design in which fibers sit in gel-filled or dry buffer tubes, protecting them from moisture and allowing length changes with temperature.

Splice closure

A re-enterable housing that protects fusion splices in outside plant; types include inline, butt, and dome closures sealed with gel or heat shrink.

Tracer wire

A wire installed alongside buried fiber so metallic locating equipment can find the route, since optical fiber itself cannot be detected by locators.

Bidirectional OTDR testing

Testing a span from both ends and averaging the results, which removes errors caused by differing backscatter coefficients at splices and events.

Duct fill ratio

The percentage of a conduit's cross-section occupied by cable; keeping it around 40 to 50 percent or less leaves room for pulling and future cables.

Power budget

The difference between transmitter output power and receiver sensitivity; it must exceed total link loss plus a margin, typically 3 dB, for the link to work.

Link loss calculation

Total loss equals connector count times connector loss, plus splice count times splice loss, plus fiber length times attenuation at the operating wavelength.

PON split ratio

The number of subscribers sharing one feeder fiber, commonly 1:32 or 1:64; a 1:32 splitter adds roughly 16 to 17 dB of loss to the budget.

Diverse routing

Designing physically separate cable paths so a single cut, fire, or construction event cannot disable both working and protection paths.

Optical margin

Extra loss allowance added to a design, often 3 dB, to cover aging, repairs, additional splices, and measurement uncertainty over the system life.

One-jumper reference

A test method using a single reference cord at each end, yielding lower measured loss than two- or three-jumper methods; the method must be reported with results.

OTDR dead zone

The distance after a reflective event where the OTDR cannot detect another event; shorter pulse widths reduce dead zones but shorten measurement range.

Index of refraction setting

The IOR value entered in an OTDR, taken from the cable manufacturer; an incorrect value makes all reported distances inaccurate.

Visual fault locator

A visible red laser tool that reveals breaks, tight bends, and damaged connectors by glowing at the fault; it does not measure loss.

GPON wavelengths

Gigabit PON uses 1490 nm downstream, 1310 nm upstream, and 1550 nm for optional video overlay, with 2.488 Gbps down and 1.244 Gbps up.

XGS-PON

A symmetric 10 Gbps PON standard using 1577 nm downstream and 1270 nm upstream, able to coexist with GPON on the same fiber via wavelength multiplexing.

Optical network terminal

The subscriber-side device in an FTTH network that converts optical signals to electrical service; receive power must fall within the PON optics window.

Drop cable

The small fiber cable, often one or two strands, running from the splitter or pedestal to the subscriber's ONT; it must be protected from tight bends and UV.