Carrier and field slang for a fiber with transmitters on it and traffic moving, also described as live or hot. A lit fiber must not be cut, bent hard or disconnected without an approved maintenance window, and the light in it can be invisible infrared at eye-damaging power. Lit service also means a carrier sells bandwidth over its own equipment instead of leasing dark glass.
Tube 4 is lit, all twelve, so mid-span the cable carefully and don't even touch the brown tube.
Never look into a fiber end or connector to see if it is lit: the light is infrared and invisible. Use a power meter or identifier.
Also heard as
- live
- hot
- in service
Related terms
Dark fiber
Installed fiber with no transmission equipment attached, either spare or leased bare to a customer who lights it.
Fiber identifier
A clip-on tester that detects light in a fiber through a gentle bend, without cutting it or interrupting traffic.
Lambda
A single wavelength channel on a fiber, named after the Greek letter used for wavelength.
Light levels
The transmit and receive optical power readings on a transceiver, read from a meter or the switch's optic diagnostics.