Telecom Equipment, Installation and Maintenance
What this domain covers
The hardware you install and keep running - from the subscriber's ONT to the exchange MDF - plus the procedures and test instruments used in the field.
Core rules
- Key items: telephone instrument, EPABX, MDF/IDF with punch-down blocks, DDF, LIU/ODF, OFC joint closure, splitter, ONT/ONU, media converter, router/switch, modem, BBU with RRU at a BTS, antenna feeders, UPS and battery bank, earthing and lightning arresters.
- Bend radius: keep fibre above roughly 20 times cable diameter while pulling and 10 times after installation; never kink drop cable.
- Splicing: fusion splice loss about 0.05–0.1 dB; connector about 0.3–0.5 dB. Clean and cleave before every fusion.
- Earthing: telecom earth pits are commonly specified below 5 ohm, tighter for sensitive equipment; test with an earth tester rather than assuming.
- Power: vented lead-acid cells read 1.215–1.240 specific gravity when fully charged and float at about 2.23–2.27 V per cell at 25 °C.
- Maintenance types: preventive (scheduled), corrective (fault-driven), predictive (alarm and trend based). Record every docket.
Worked example
Link budget: transmitter −3 dBm, receiver sensitivity −28 dBm, so the budget is 25 dB. For 8 km of fibre at 0.35 dB/km (2.8 dB), four fusion splices at 0.1 dB (0.4 dB) and two connectors at 0.5 dB (1.0 dB), total loss is 4.2 dB, leaving a 20.8 dB margin. The link passes. Reasoning: the power margin, not the individual loss figure, shows whether the design is safe.
Traps
- Using an OTDR as a power meter - the OTDR locates events and distance; the power meter measures level.
- Forgetting connector loss in the budget.
- Bending fibre below the minimum radius and creating macrobend loss.
- Working on a battery bank while wearing metal jewellery.