1. Scope
Defines how loss budgets shall be calculated, documented and verified for every designed link, including PON ODNs.
2. Normative requirements
2.1 Available budget = minimum transmitter power − end-of-life receiver sensitivity − system penalties, using vendor worst-case values.
2.2 Consumed budget shall sum: fiber at worst-case coefficient (design values: 0.36 dB/km @1310, 0.25 @1550 single-mode unless datasheet is worse); 0.75 dB per mated connector pair (0.5 dB where low-loss is specified and verified); 0.10 dB per planned splice; splitter and filter losses at vendor maximum; and repair allowance of 0.05 dB/km.
2.3 A lifetime margin of ≥2.5 dB shall be included and shall not be consumed at design time.
2.4 PON designs shall verify both the farthest ONT against the ODN class limit (e.g., 28 dB for Class B+) and the nearest ONT against receiver overload.
2.5 The budget workbook shall be versioned, delivered with the design, and used unchanged as the acceptance comparison per FOI-S-002.
3. Acceptance criteria
A design is compliant when every link's consumed budget plus margin fits the available budget at all service wavelengths, and the workbook accompanies the design package.