Network unit and method for monitoring a fiber line

A network unit for monitoring a fiber line between a radio base station and a radio head in a Fiber to the Radio head communications network, which Fiber to the Radio head communications network comprises a ring architecture or a tree architecture of fiber, with Subcarrier Multiplexing, SCM, downstream transmissions and Wavelength Division Multiplexing, WDM, upstream transmissions, wherein the network unit comprises, for monitoring the fiber line:

• a detecting circuit configured to detect an indication of a fault along the fiber line based on monitored power;
• an Optical x Domain Reflectometry, OxDR, circuit configured to initiate, in response to the indication being detected, an OxDR measurement over the fiber line;
• and
• an analyzing circuit configured to analyse a trace from the OxDR measurement for localizing the fault or for deciding that the indicated fault is not a fault along the fiber line.

A computer readable medium containing computer-executable instructions which, once executed by a processor in a network unit, causes the network unit to:

• detect an indication of a fault along the fiber line based on monitoring power;
• in response to the detected indication, initiate an Optical x Domain Reflectometry, OxDR, measurement over the fiber line;
• and
• analyze a trace from the OxDR measurement for localizing the fault or for deciding that the indicated fault is not a fault along the fiber line.