Fiber optic network design and project management
Network design and project management tests whether you can turn requirements into a buildable, testable fiber project. Expect topology and media selection, fiber-count sizing, loss-budget allocation, standards references, schedule and acceptance planning, and documentation-not just installation mechanics.
Design inputs and topology
Start with distance, bandwidth, protocol, environment, growth, redundancy, and code. Point-to-point suits simple links; star suits premises; ring provides resilience. Select media by reach: OM4 for 10GBASE-SR up to 400 m, OS2 for longer campus/OSP and 10GBASE-LR/ER. Size fiber count from active pairs plus spare-commonly 25–50% spare and a minimum of 6 or 12 fibers per route-and consider diverse paths for critical links. Design the loss budget before purchase: fiber, connectors, splices, splitters, and margin.
Project management
Use phases: requirements, design, bill of materials, schedule, installation, testing, acceptance, closeout. Assign roles for installer, splicer, tester, inspector, and owner. Control submittals, RFIs, change orders, and safety. Require TIA-606 labels, as-builts, test reports, and warranty documents at closeout. Acceptance criteria must be written before testing.
Worked example
A 1 km link between two buildings needs 10 Gbps now and 40 Gbps later, with 12 fibers active. OM4 at 10GBASE-SR is limited to 400 m, so it fails at 1 km; OS2 with 10GBASE-LR passes. Add 50% spare to 12 active fibers = 18, round up to 24 fibers. Loss check: 1 km × 0.4 dB = 0.4 dB; two connector pairs × 0.75 = 1.5 dB; total 1.9 dB; plus 3 dB margin = 4.9 dB. If the chosen optics budget is 10 dB, the design passes. Document the media choice, count, and budget in the design package.
Traps
Sizing to active fibers only; using OM3/OM4 beyond reach; omitting margin; designing without acceptance criteria; no as-builts; and treating project management as paperwork rather than loss-budget and schedule control. Also watch for splitter loss being left out of PON budgets.