Greenfield FTTH design for 500 homes, full OSP package from plat to BOM
A private greenfield builder bringing GPON fiber to a new 500-home suburban subdivision, designed to the same OSP pattern Pathworks uses for subcontracted packages under BEAD/RDOF-funded rural cooperatives.
- Input received
- The subdivision plat with lot layout and home count (~4 homes/acre), the target GPON architecture, and local joint-trench and AHJ burial requirements.
- Delivered
- A complete outside-plant design: two-stage centralized/distributed GPON topology (FDH/FDT), civil route and handhole plan, fiber count and splice architecture by tier, a cumulative optical link budget, and a procurement-ready bill of materials.
- Timeline
- Scoped in 26 hours, delivered in 13 business days.
Built to standard US ILEC/CLEC practice: a two-stage 1:4/1:8 split localizes fault response to a single FDT instead of the whole feeder, construction runs underground-first to meet HOA aesthetic requirements, and 20–30% spare fiber is held at every tier so the network can absorb infill lots without a re-trench. The design closes with 7.4 dB of optical margin against the 28 dB GPON Class B+ budget — enough headroom for a future 1:64 upgrade at a subset of FDTs.
- Homes passed
- 500
- Effective split
- 1:32
- Link margin
- 7.4 dB
- Feeder route
- 1.8 mi
Splice architecture by tier
- CO exit — rack-mount ODF, 144F capacity, 144 fusion splices, pigtail-to-feeder
- FDH (curb cabinet) — 1:4 splitter in an in-cabinet tray, 4 splitters plus 144F passing through, ribbon mass fusion preferred
- FDT (pedestal) — 1:8 splitter, 8 splitters across 16 FDTs, in-ground rated
- NID (premise) — mechanical/factory connector, zero splices, field-terminated only if the drop is cut to length
Splice loss is held to 0.1 dB per fusion splice, consistent with Telcordia GR-326 fusion performance criteria — the number the optical link budget above is built on.
Bill of materials, summary
- Feeder cable — 144F loose tube, gel-filled, armored, underground, 1.8 mi
- Distribution cable — 24F ribbon, underground rated, 1.2 mi across 4 legs
- Drop cable — 1F flat, self-supporting where aerial, 500 units at an average 150 ft
- FDH cabinet — 288F capacity, 1:4 splitter bank, 1 unit
- FDT pedestal — 1:8 splitter, 24-port, 16 units
- NID — single-port, weatherproof, SC/APC, 500 units
- Handholes — 17×30 in polymer concrete, 18 units
- HDPE conduit, 2 in — SDR-11, 1.8 mi
Why these specific calls
1:32 over 1:64 split — protects optical margin given the feeder distance, and avoids forcing a high-power OLT card purchase the client didn't ask for.
Centralized FDH, distributed FDT — matches standard US ILEC practice and localizes fault response to one FDT rather than the whole feeder.
20–30% spare fiber at every tier — the same discipline applied on passive ODN designs elsewhere; the US-specific addition here was coordinating that spare capacity with joint-trench utility scheduling and the deeper AHJ-mandated burial depths this jurisdiction requires.
Underground-first construction — driven primarily by HOA and municipal aesthetic requirements typical of US greenfield subdivisions, with long-term reliability as a secondary, welcome benefit rather than the primary driver.
Design work followed TIA-568/598 and Telcordia GR documentation standards throughout, with NESC governing the two aerial road crossings.
More case studies
340-home FTTH rollout, from a marked-up street map
The client's planning team had the route in their heads and on a napkin-grade map. Pathworks turned it into a construction-ready package without a single site visit.
Warehouse electrical retrofit, permit-ready in under two weeks
Field access was limited to two short walk-throughs. The drafting was done entirely from photos and the contractor's own markups.
Municipal drainage upgrade from a rough site sketch
The consultancy's own drafters were fully booked on a larger tender. Pathworks cleared the backlog item without disrupting their internal schedule.