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400G Ethernet Fibre Cabling

Delivered via the M Series: From the UK’s MTP® Specialists

400G Fibre Cabling

400G Ethernet – Overview

It doesn’t seem long ago that we were looking at the introduction of the first 40G Ethernet ports. This year heralds the ratification of the IEEE 400G standard, 802.3cm for multimode and 802.3bs for singlemode (not to mention similar standards: Telcordia GR-326 Core and TIA 604-18 (FOCIS 18) IEC 61754-7-3).

Up to now there has been variation in the transmission of data rates above 100G by the various equipment manufacturers and this has led to great debate about how to best create the structured network that will be future proof as the “winning” method emerges, if a winning method emerges at all.

Working with our long term partner US Conec (who are a key member of the standards board) Complete Connect has always been in a position to ensure we can provide the cabling required for all types of transmission. This has led to us developing cables with MTP connectors with 8 fibre, 12 fibre, 16 fibre, 24 fibre and 48 fibre over the last 10 years.

Below we discuss the current state of play.

mpo mtp 16 fibre connector with offset key

Cabling for 400G requires even more fibres per connector

Table 1 – 400G over Multimode Fibre

Transmission Complete Connect Series Data Rate Per Channel Fibre Cores Per 400G MTP MPO Connector
400GBASE-SR16 M1600 Series 25G 32 32
400GBASE-SR8 M800 Series 50G 16 16
400GBASE-SR4 M400 Series 100G 8 8

400G Ethernet: Variations in Transmission over Multimode Fibre

At the time of writing, there are emerging various ways to achieve 400G data rates. These include parallel lane transmission over fibre (both singlemode and multimode) via 4 x 100G, 8 x 50G and 16 x 25G using both OSFP and QSFP-DD transceivers, very short range DAC cables and AOC.

Complete Connect offer fibre cables to accommodate all these variations. Transmission over multimode fibre (offering distances up to 100m) are summarised in table 1 opposite.

The M Series cabling you require will depend on the choice of transceiver, which varies depending on the host equipment manufacturer.

The MX Series of cassettes and housing panels offers options that cover all bases and provide the ability to create fibre access points (FAPs) with LC port or MTP port presentation.

400G Ethernet: Variations in Transmission over Singlemode Fibre

Transmission over multimode fibre is relatively straightforward compared to over singlemode fibre.

As with 40G and 100G transmission, where the four 10G (or 25G) lanes can transmit over separate fibres (4 Tx and 4 Rx) or over separate wavelengths (4 different wavelengths for 4 channels) on the same fibre pair (1 x Tx and 1 Rx), 400G operates in a similar fashion.

Similarly, this also enables some singlemode 400G ports to be connected to multiple lower data rate ports (4 x 100G or 8 x 50G etc) or only directly to another 400G port.

Singlemode 400G transceivers are currently using three types of port: MTP MPO 8 fibre , LC duplex (2 fibre) and CS Quad (four fibre). These each the different breakout connectivity options through direct fibre cabling.

Table 2 – 400G over Singlemode Fibre

Transmission Complete Connect
Data Rate
Per Channel
Fibre Cores
Per 400G
MTP MPO Connector
Or Other
As Used by
M400 Series 100G 8 8 OSFP Arista only
M400 Series 100G 8 8 OSFP Arista only
M310 Series 50G 2 LC Duplex OSFP Arista only
400GBASE-2FR4 **
M310 Series 100G 4 CS Quad Arista only
M310 Series 100G 2 LC Duplex TBC
M310 Series 100G 2 LC Duplex TBC


(*) breakouts out to FR, (**) breakouts out to 2 x CWDM4

M400 Series 100G to 50G

M1600 Series Conversion Cable

400G SR8, the M800 Series, IEEE 802.3cm and other standards

The M800 Series offers customers a complete fibre cabling system using the MTP 16 fibre connector and 16 core fibre cables in accordance with IEEE 802.3cm, Telcordia GR-326 Core and TIA 604-18 (FOCIS 18) IEC 61754-7-3.

Complete Connect’s M800 Series offer customers a complete range of options for adding 400G ports in both multimode (short range) and singlemode (long range). Using the industry leading MTP 16 fibre connector and micro core high density fibre cables with Corning glass cores, our low loss cabling system ensures optimal performance.

The M800 Series includes 400G patch cords for direct connection between QSFP-DD 400G transceivers or OSFP transceivers, 400G conversion cables to connect to multiple 200G (or 100G) transceivers and also cables to connect into existing MTP infrastructure.

Looking for further information, talk with one of our experts online…


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