Dark fibre
Also called: unlit fibre · Topic: Transport and Communication in India · NCERT: Beyond NCERT
Meaning
Dark fibre (also called unlit fibre) is optical fibre cable that has been laid but is not carrying any data. Optical fibre is a thin glass thread that carries information as pulses of light. A cable is "dark" when no equipment at either end is sending light through it. Firms usually lay extra fibre, because laying cable costs far more than the glass itself. That spare fibre can be leased (rented) to private telecom companies. Leasing earns money to run and maintain the network, and it puts unused capacity to work.
Example
BharatNet has laid optical fibre to India's gram panchayats (village councils). The CAG's Audit Report No. 19 of 2026 found that much of this dark fibre was never leased. In some states there was no leasing policy. In others, the State Implementing Agency was slow to decide. So the fibre sat idle when it could have earned revenue.
Don't confuse with
- Lit fibre: this fibre is connected to working equipment and is already carrying data. Dark fibre has been laid but carries nothing.
- Service-ready gram panchayat: this is a BharatNet term. It means the fibre has reached the village and the equipment is installed. It does not mean anyone is using the line. A service-ready GP can still be offline, but that is not the same as unleased dark fibre.