FOA CFOS/DAS flashcards

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

Link loss budget

The maximum allowable optical loss between transmitter and receiver, equal to transmitter output power minus receiver sensitivity. Design losses plus margin must stay below this figure.

Receiver sensitivity

The minimum optical power at which a receiver achieves its specified bit error rate, usually expressed in dBm. It sets the lower limit of the link loss budget.

Design margin

Extra loss allowance, typically at least 3 dB, added to calculated link loss to cover aging, repairs, temperature effects, and future splices.

Modal dispersion

Pulse spreading in multimode fiber caused by different modes traveling different path lengths. It limits bandwidth and distance, especially at 850 nm with older fiber grades.

OM4 fiber

Laser-optimized 50/125 µm multimode fiber with high bandwidth. It supports 10GBASE-SR to roughly 400 m and is common in data-center and building backbones.

OS2 fiber

Single-mode 9/125 µm fiber with low attenuation at 1310 and 1550 nm. It is used for campus, metro, and long-reach links beyond multimode distance limits.

Connector loss allowance

The dB budgeted per mated connector pair in a loss calculation. Common design values are 0.5 dB for field-terminated and 0.3 dB for factory connectors.

Splice loss allowance

The dB budgeted per fusion splice in a loss calculation, typically 0.1 to 0.3 dB. Actual measured splice loss should be verified with OTDR testing.

Bend radius rule

Minimum cable bend is about 10× outside diameter under load and 20× when pulling. Tighter bends cause loss and long-term fiber damage.

Polarity method A

A duplex patch cord wiring scheme where the transmit position at one end maps to the receive position at the other, using straight-wired cords and keyed adapters.

Polarity method B

A duplex wiring scheme using a crossover patch cord at one end so transmit pairs align with receive pairs across the link. Method must stay consistent end to end.

10GBASE-LR reach

A single-mode 1310 nm Ethernet standard with roughly 10 km reach. Actual distance depends on the transceiver link budget, splice count, and connector losses.

Attenuation coefficient

Fiber loss per unit length in dB/km at a given wavelength. It drives total span loss and is multiplied by route length in the loss budget.

Optical return loss

The ratio of reflected to incident power at an interface, in dB. Poor return loss from bad connectors or tight bends degrades transmitter performance and link stability.

Route diversity

Design practice of providing physically separate cable paths so a single cut or disaster cannot disable both links. It is a reliability requirement in critical networks.

Work breakdown structure

A hierarchical decomposition of project scope into manageable deliverables. Each task in the schedule should map to exactly one WBS element.

Critical path

The longest chain of dependent tasks through the schedule network. It has zero float, so any delay on it delays project completion.

Float (slack)

The amount of time a task can slip without delaying the project finish. It equals late start minus early start, or late finish minus early finish.

Cost variance (CV)

Earned value minus actual cost. A negative CV means the project has spent more than the value earned to date.

Schedule variance (SV)

Earned value minus planned value. A negative SV means work is behind the planned schedule baseline.

Cost performance index

Earned value divided by actual cost. A CPI below 1.0 indicates cost overrun; above 1.0 indicates better-than-planned cost efficiency.

Schedule performance index

Earned value divided by planned value. An SPI below 1.0 indicates the project is behind schedule relative to the baseline.

Estimate at completion

Projected total cost, often calculated as actual cost plus estimate to complete. A common formula is EAC = BAC divided by CPI.

Budget at completion

The total approved budget for the project baseline. It is compared with earned value and actual cost to compute variance and performance indices.

Risk register

A log of identified risks with probability, impact, owner, and response strategy. Responses include avoid, mitigate, transfer, and accept.

Change control board

The group that reviews and approves or rejects scope, schedule, and cost changes. Approval updates the baseline before work proceeds.

Cost of quality

Total cost of prevention, appraisal, and failure. Prevention and appraisal spending usually reduces expensive rework and warranty failure costs.

Punch list

A documented list of incomplete or defective work items found at inspection. Closeout requires resolving each item before final acceptance.

As-built drawings

Final drawings reflecting actual installed routes, splice locations, and fiber assignments. They are a required closeout deliverable for acceptance and future maintenance.

Acceptance testing

Formal verification that installed links meet specified loss and OTDR criteria. Passing results trigger milestone payment and start of the warranty period.

Procurement lead time

The interval between ordering and receiving materials such as cable or transceivers. Long lead times are scheduled early and tracked as schedule risk.

Milestone

A zero-duration schedule marker representing a significant event, such as test completion or owner acceptance. Milestones carry no work but anchor reporting.