Method for monitoring a fiber based network, method for determining a delay in a fiber based network, fiber based network, and reflecting unit

A method for determining a delay between a start port at a star point of a fiber based network with a star topology and an end port of one of the branches of the fiber based network, wherein said branch comprises a start port for connection to the star point and an end port for connection to an end device, the method comprising at least the steps of:

• connecting a two-port bidirectional partially reflecting unit, TPBPRU, with a first port of its two ports to said branch facing the direction of the start port, wherein the two-port bidirectional partially reflecting unit, TPBPRU, is configured to partially reflect signals entering it from both of its two ports with the same delay;
• connecting a calibrating delay measurement device with a first calibration fiber to a second port of the two ports of the two-port bidirectional partially reflecting unit, TPBPRU;
• generating a first calibration signal and inserting it into the first calibration fiber, by the calibrating delay measurement device, while the start port of the branch is unconnected or connected to a reflective device with negligible delay or known delay from the start port to the location of reflection of the reflective device;
• and
• determining a delay between a receiving of a first reflection of the first calibration signal,
• generated at the two-port bidirectional partially reflecting unit, TPBPRU, and a receiving of a second reflection of the first calibration signal,
• generated at the unconnected start port or at the reflective device, respectively.

A two-port bidirectional partially reflecting unit, TPBPRU, for a fiber based network, comprising:

• a first end surface of a first fiber and a second end surface of a second fiber facing one another, wherein the first fiber and the second fiber are aligned along a common longitudinal direction in the volume in which the first end surface and the second end surface are arranged;
• wherein the first end surface is arranged essentially in perpendicular to the longitudinal direction;
• and
• wherein the second end surface is formed and arranged at an angle with respect to the first end surface, creating a wedge-form gap between the first end surface and the second end surface.

A fiber based network with a star topology having a star point and a plurality of branches, comprising:

• a delay measurement device;
• a reflecting unit arranged at an end of each branch connected in parallel to or in front of an end port for connecting an end device to the fiber based network at said branch;
• the delay measurement device being configured to:
• insert a respective test signal into each of a plurality of branches;
• and
• measure a delay between the inserting of the respective test signal and a receiving of a respective reflected signal for each of the branches, the respective reflective signal being generated, at each branch of the plurality of branches, by the respective reflecting unit.