Data Centre Interconnect Fibre Testing: Testing High-Speed Optical Links

FDNS Blogs

Oct 1

3 min read

Why Data Centre Interconnect testing matters

Data Centre Interconnect (DCI) links can carry critical traffic between separate data halls, campuses or facilities. The physical fibre path needs to be tested for the transmission system it will support, not simply checked for continuity.

A DCI test programme can combine end-to-end insertion-loss measurement, optical return loss, OTDR characterisation, connector inspection and, where required, fibre characterisation such as chromatic dispersion (CD) and polarisation mode dispersion (PMD).

What is Data Centre Interconnect?

Data Centre Interconnect connects separate data centres or data-centre buildings using high-capacity network links. Depending on distance and capacity, the optical system may use direct Ethernet optics, CWDM, DWDM, coherent transmission or amplified optical networks.

Tier 1 fibre certification for DCI

First, establish the physical link as a sound optical path. End-to-end insertion-loss testing measures attenuation between the defined test points, while optical return loss can identify reflection performance that may matter to the transmission system.

Include fibre end-face inspection and cleaning in the test workflow. Poor connector condition can introduce loss and reflection that may otherwise be mistaken for a transmission-system problem.

OTDR testing on Data Centre Interconnect links

OTDR testing provides event-level information along the fibre, helping identify splice losses, connector events, bends, breaks and other anomalies. Launch and receive fibres help characterise the ends of the link, and you should select test settings for the fibre type, link length, and measurement objective.

For critical DCI links, bi-directional OTDR testing can provide a stronger interpretation of individual event losses than relying on a single direction.

CWDM and DWDM fibre testing

CWDM and DWDM systems place additional requirements on the optical path. The fibre must be suitable for the intended wavelengths, link distance, and transmission equipment. Basic loss testing and OTDR are therefore part of a wider commissioning process rather than the entire transmission test programme.

When CD and PMD testing becomes important

As transmission rates and link distances increase, fibre impairments such as chromatic dispersion and polarisation mode dispersion can affect system performance. OTDR does not measure CD or PMD, so the intended optical transmission system may require specialist fibre characterisation.

FDNS provides CD/PMD fibre testing and characterisation for high-capacity optical networks.

High-speed Ethernet and BERT testing

Where the DCI carries high-speed Ethernet, physical fibre certification may need to be followed by transmission testing. BERT and FEC-related measurements can help establish whether the complete optical path and transmission system perform correctly at the intended data rate.

See the FDNS High-Speed Ethernet, BERT & FEC Testing service for specialist transmission testing.

Standards-based DCI testing

The applicable project specification and transmission system determine the required measurements. ISO/IEC 14763-3:2024 provides the current framework for inspection and testing of installed optical fibre cabling, while specific IEC measurement standards address individual test methods.

How FDNS supports Data Centre Interconnect testing

FDNS can support DCI projects from fibre installation and certification through OTDR, insertion-loss testing, fibre characterisation, CD/PMD and high-speed BERT testing. Our Data Centre Interconnect Solutions service can be linked directly to the testing programme.

Frequently asked questions

What is Data Centre Interconnect testing?

It is the testing and characterisation of the optical links used to connect separate data centres or facilities.

Is OTDR testing enough for a DCI link?

No. OTDR provides event-level information, but end-to-end insertion loss and other measurements may also be required depending on the system and specification.

When is CD/PMD testing required?

CD/PMD testing is considered when transmission speed, distance and optical system design make fibre characterisation relevant to performance.

Does a DCI link need BERT testing?

Where the project requires validation of high-speed Ethernet transmission, BERT and related measurements can form part of the commissioning programme.