GPON ONT Won't Range After a New Drop
A new FTTH customer in a 1:32 GPON splitter area has no service; the ONT power LED is green but the PON LED blinks. At the ONT, you measure 1490 nm downstream at -29.8 dBm. Design records show the OLT launch is +3 dBm, feeder 7.4 km at 0.35 dB/km, splitter insertion loss 17.2 dB, drop 140 m at 0.34 dB/km, plus four connectors at 0.3 dB each. The splitter sits in a pedestal 7.4 km from the CO. A visual fault locator shows a bright glow at a sharp bend where the drop is stapled behind a downspout about 25 m from the ONT. The ONT is rated for -27 dBm sensitivity. The customer refuses to let you re-route the interior fiber because it is behind newly installed siding.
1. Calculate the expected receive power at the ONT. Does the measured -29.8 dBm explain the blinking PON LED?
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Feeder: 7.4 km x 0.35 dB/km = 2.59 dB. Splitter: 17.2 dB. Drop: 0.140 km x 0.34 = 0.048 dB. Connectors: 4 x 0.3 = 1.2 dB. Total passive loss = 21.04 dB. Expected RX = +3 - 21.04 = -18.0 dBm. Measured -29.8 dBm is 11.8 dB worse than design. A GPON ONT with -27 dBm sensitivity cannot range at -29.8 dBm, so the blinking PON LED is consistent with loss of downstream signal. The VFL glow at the bend shows light escaping, which is a strong indicator of macrobend loss; 11.8 dB is too much for a single connector but plausible for a tight bend or a kinked drop. Do not assume the bend is the only fault; the connector at the ONT may also be dirty.
2. What is the correct repair sequence, and how do you interpret the VFL glow?
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First clean and inspect both connectors, then relieve the bend. If the fiber is kinked or the bend radius cannot be maintained, replace the drop section rather than stapling it tighter. Use an OTDR or OLTS to measure the drop before and after; a VFL only shows visible light leakage, not loss magnitude. Verify the receive level is at least -27 dBm with margin, then confirm the ONT ranges and the customer's service activates. If the level improves but is still marginal, check the splitter port and feeder connector. Document the before/after readings and the bend location.
3. The customer refuses the interior reroute. What are your options, and how do you document the decision?
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Do not force entry or run fiber in a way that violates the customer's property. Explain that the current route is the likely cause and that leaving it will keep the service down. Offer alternatives: an exterior route around the siding, a surface raceway inside with written consent, or a later appointment with a construction tech. If the customer still refuses, document the refusal, note that service cannot be guaranteed, and escalate to a supervisor. Do not reconnect and leave a known bad bend in place just to close the ticket.