FttH and Optical distribution network reliability

Widely based on international technical reports, this document gives the key elements and rationale for ensuring optical networks reliability.

This newsletter deals with the key parameters and rationale to choose right optical fibres and optical fibre cables allowing optical distribution infrastructure long-term reliability.

Special attention is paid to the optical fibres stresses and strains related to the constraints that this optical distribution network would face in its lifetime. This paper describes how to manage these stresses and strains on the optical fibres by
choosing the right fibres and cables.

In 2020, Europacable published the white paper “Expected lifetime of Passive Optical Infrastructure”. Readers should also refer to this document.
Optical Fibre Distribution Network (OFDN) reliability:
To ensure the robustness of optical fibre networks and to optimise their service life, the following two elements have to be considered.

• The optical reliability: Which ensures that the transmission of the optical signal will not deteriorate over the lifetime of the OFDN.
• The mechanical reliability: Which ensures that the fibres will not breakduring the lifetime of the OFDN.

Whatever the stresses to which the OFDN is exposed, the choice of the right optical fibres associated to well-designed cables are key elements?

The optical Fibre type – a fundamental choice:
The optical fibre type strongly determines the resilience of the network to the different events that it will experience during its lifetime. These “events” will generate bending stresses on the optical fibres (micro-bending or macro-bending).

To decrease the sensitivity to these bending stresses (macro and micro-bending), the choice of G.657.Ax optical fibres is highly relevant.

What about fibre compression?

The following chart summarizes the different sensitivity of two fibre types for an equivalent micro-bending stress induced by fibre compression (laboratory tests).

Download the documentation