FOA CFOS/FC flashcards

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

IEC 61300-3-35

International standard defining endface zones and pass/fail criteria for fiber connectors; specifies defect sizes allowed in core, cladding, adhesive, and contact zones.

Zone A core

The central core region of a single-mode connector endface; any scratch, pit, or particle here is a fail under IEC 61300-3-35.

Wet-dry cleaning

Cleaning method using 99% isopropyl alcohol on a lint-free wipe followed by a dry wipe; removes stubborn residue and must end with a dry pass.

Inspection magnification

200x is used for multimode ferrules; 400x is used for single-mode ferrules and for judging fine scratches and pits.

VFL wavelength

Visible fault locator uses about 650 nm red light; it escapes at bends and breaks to mark fault locations on dark fiber.

VFL range limit

High attenuation at 650 nm limits VFL use to a few kilometers in single-mode and less in multimode; longer links need an OTDR.

Fiber identifier

Clamp-on instrument that detects traffic or a tone on a fiber without bending or disconnecting it; used for tracing and direction checks.

dBm definition

Absolute optical power referenced to 1 mW: P(dBm) = 10 log10(P(mW)/1 mW); 0 dBm equals 1 mW and -10 dBm equals 0.1 mW.

Calibration wavelength

The wavelength at which a power meter's detector response is calibrated; the meter setting must match the source wavelength to avoid error.

Reference power

Power measured with the source connected directly to the meter through the reference jumper; subtracted from the far-end reading to give link loss.

One-jumper reference

Reference method using a single launch jumper; suited to links with one connector at each end and avoids counting an extra connector.

Two-jumper reference

Reference method using two jumpers; used for links with patch panels at both ends so the reference includes the same connector count as the link.

Insertion loss formula

Insertion loss in dB equals reference power minus measured far-end power; reported as a positive number for a passing link.

OTDR distance formula

Distance = (c/n) x t / 2, where n is the fiber index of refraction and t is the round-trip time of the backscattered pulse.

Attenuation dead zone

Distance after a reflective event where a subsequent event cannot be measured within a specified loss accuracy; reduced by using a shorter pulse.

IOR setting

Index of refraction entered into an OTDR; a 1% IOR error produces about a 1% error in reported distance.

Launch and receive fibers

Tail fibers attached to both ends of the link under test; they move the first and last connectors out of the OTDR dead zones.

OTDR gainer

A splice that appears as negative loss; caused by backscatter coefficient mismatch between fibers, not by real gain, and corrected by bidirectional averaging.

Optical power meter

Instrument measuring absolute optical power in dBm or microwatts; paired with a stabilized light source it performs insertion loss testing.

Optical return loss meter

Instrument measuring reflected power from a link; ORL matters for analog video and high-speed links where reflections degrade performance.

Optical spectrum analyzer

Instrument displaying power versus wavelength; used to verify CWDM and DWDM channel presence, spacing, and power levels.

Single-mode attenuation

Typical values are about 0.35 dB/km at 1310 nm and 0.20 dB/km at 1550 nm; used in loss budget calculations.

Connector loss allowance

Budget planning uses about 0.3-0.5 dB per mated pair, with 0.75 dB as a worst-case value for conservative designs.

Splitter loss values

Typical splitter insertion loss: 1:2 is 3.5 dB, 1:4 is 7.2 dB, 1:8 is 10.5 dB, 1:16 is 13.8 dB, and 1:32 is 17.0 dB.

Design margin

Extra loss allowance, commonly 3 dB, added to a budget for aging, repairs, temperature changes, and future modifications.

Chromatic dispersion

Pulse broadening in ps/nm/km caused by wavelength-dependent propagation speed; limits high-bit-rate links and is near zero at 1310 nm in standard single-mode.

Polarization mode dispersion

Differential delay between polarization states, in ps/sqrt(km); it limits 10G and higher links and is measured with a PMD analyzer.

Multimode bandwidth

Modal dispersion limit specified in MHz·km, such as OM3 at 2000 MHz·km at 850 nm; it caps distance at a given bit rate.

PON wavelengths

Downstream is 1490 nm, upstream is 1310 nm, and video overlay is 1550 nm; test ports commonly use 1625 or 1650 nm to avoid live traffic.

PON OTDR testing

A PON-optimized OTDR with sufficient dynamic range tests through splitters; individual drops are isolated by testing from the ONT side.

Filtered power meter

Power meter with a wavelength-selective filter that separates upstream 1310 nm from downstream 1490 nm on a live PON.

Connector repeatability

Variation in measured loss each time a connector is mated, typically 0.1-0.5 dB; it contributes to overall measurement uncertainty.