FOA CFOS/C flashcards

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

Numerical aperture

NA = sqrt(n_core^2 - n_cladding^2); it describes the light-gathering ability of a fiber and relates to the maximum acceptance angle by sin(theta_max) = NA.

Total internal reflection

Light stays in the core when it strikes the core-cladding boundary above the critical angle, which is arcsin(n_cladding/n_core). This is the basis of fiber guidance.

Graded-index multimode

A multimode fiber whose core refractive index decreases toward the cladding, equalizing path lengths and reducing modal dispersion compared with step-index multimode.

Single-mode fiber

Fiber with an 8-10 um core that supports one propagation mode, used at 1310 nm and 1550 nm for long-distance and high-bandwidth links.

OM3 and OM4

Laser-optimized 50/125 um multimode fibers; OM4 offers higher bandwidth and longer reach than OM3 for 10G and higher Ethernet applications.

Macrobend vs microbend

Macrobend loss comes from large-radius bends visible to the eye; microbend loss comes from small random stresses along the fiber axis. Both increase at longer wavelengths.

Laser safety rule

Never look into a fiber end or connector; treat all fiber as potentially live and follow laser-safety procedures and eye protection requirements.

TIA-568 categories

The standard defining copper categories (Cat 5e, 6, 6A, 8) and fiber types (OM1-OM5, OS1/OS2) for premises telecommunications cabling.

Horizontal cabling length

Maximum horizontal channel is 90 m of permanent link plus 10 m of patch cords, totaling 100 m per TIA-568.

TIA-569

The standard for telecommunications pathways and spaces, covering conduit, cable tray, and separation from power in premises installations.

TIA-606

The administration standard for labeling and documenting cables, pathways, and spaces so that the cabling system can be managed and maintained.

LC connector

A small-form-factor fiber connector with a 1.25 mm ferrule, widely used for high-density premises links and compatible with SFP transceivers.

MPO polarity methods

TIA-568 defines Method A, B, and C for MPO trunk polarity; the method determines pinning and fiber mapping end to end.

Plenum cable rating

CMP-rated cable is required in air-handling spaces; CMR is for risers, and CM/CMX for general-purpose or limited-use areas.

Pull tension limit

Typical premises fiber cable allows about 220-300 N (50-70 lbf) during installation; always follow the manufacturer datasheet limit.

Minimum bend radius

A common rule is 10x cable OD during installation and 20x OD under load; tight bends cause permanent macrobend loss.

Fusion splice loss

A well-made fusion splice typically shows 0.1 dB or less loss; splice trays must protect the splice and maintain bend radius.

Firestopping

Listed materials and methods used to restore the fire rating of walls and floors where cables penetrate, required by building codes.

Service loop

Extra cable left at both ends of an installation to allow future retermination and maintenance without re-pulling the cable.

Loss budget formula

Total link loss = fiber attenuation (dB/km x km) + connector losses + splice losses + safety margin; compare with the transceiver budget.

Tier 1 testing

Insertion loss and length measurement with an optical loss test set (light source and power meter), the basic acceptance test for fiber links.

Tier 2 testing

Adds an OTDR trace to Tier 1 results to locate events, splices, connectors, and reflections along the fiber link.

OTDR dead zone

The distance after an event where the OTDR cannot detect another event; event and attenuation dead zones differ and depend on pulse width.

Reference method

One-, two-, or three-jumper reference setups produce different measured loss; the method used must be documented in the test report.

IEC 61300-3-35

The standard defining pass/fail criteria for fiber connector end-face inspection zones, used with a fiber inspection scope.

Inspect-clean-inspect

The required sequence before mating any connector: inspect with a scope, clean with approved tools, and re-inspect to confirm pass.

Test wavelength selection

Use 850/1300 nm for multimode and 1310/1550 nm for single-mode so test results match the application's operating wavelengths.

Application requirements

Design inputs include bandwidth, distance, protocol, topology, and environment; these determine fiber type, connector, and transceiver choice.

Fiber type selection

Multimode is used for short building and campus links; single-mode is used for long-haul and high-bandwidth links where reach exceeds multimode limits.

Topology options

Point-to-point, star, ring, and passive optical LAN (PON) split architectures; each changes loss, component count, and management needs.

Project phases

Requirements, design, procurement, installation, testing/acceptance, and as-built documentation form the standard project lifecycle.

Acceptance criteria

Acceptance references the applicable standard (e.g., TIA-568, IEC 61300-3-35) and requires test reports, labeling records, and as-built drawings.