Tag Archives: 40/100G Ethernet

How to Get 40/100G Connectivity in Your Data Centre?

The demand for network growth is rapidly increasing, which is due to the massive amount of storage needed for high bandwidth applications. Large growth hence spurs the requirements for expansion and scalability in the data centre. Cabling infrastructures must evolve to provide reliability, manageability and flexibility. Obviously, the conservative 2-fibre transmission is not enough to catch up with the speed. And 12 or 24-fibre 40/100G Ethernet migration is quickly becoming a matter of survival. This article offers cabling solutions for cost-effective and simplified migration for 40/100G within the data centre.

Introduction to 40/100G Ethernet

40/100G Ethernet employ parallel optics. Parallel optics transmission, compared to traditional serial transmission, uses an optic module interface where data is simultaneously transmitted and received over multiple fibres. For the 40GE transmission, 4 x 10G on 4 fibres per direction and 10 x 10G on 10 fibres per direction for the 100GE. Which ushers the need for the high quality and low loss multimode MTP connectors and assemblies.

How to Get 40G Connectivity?
1). 10G to 40G Connection

Migration from 10G to 40G system utilises 40G MTP/MPO breakout cables, with an MTP/MPO connector on one end and four duplex LC connectors on the other end. The IEEE ratified the 40GBASE-SR4 (MPO/MTP interface) standard that uses 4 lanes at 10G SFP+ (LC interface) per lane over multimode fibre for a total of 8 fibres.

Parallel optics 40GBASE-SR4 uses 8 out of 12 MTP/MPO interfaces fibres transmitting 4 duplex channels (4 for transmit and 4 receive), as shown in the following picture. QSFP+ to SFP+ breakout cable is 8-fibres MTP to LC breakout assembly.

10G-40G migration solution 1

2). 40G to 40G Connection

As for data transmission between two 40G switches, 40G QSFP+ SR4 transceivers are generally adopted, transmitting signals over four duplex 10G lanes (4 transmit and 4 receive). A 12-fibreMTP/MPO trunk are involved, with 8 out of 12 fibres used to achieve 4 duplex signals transmission. And MTP/MPO adapter panels can be installed easily to make the next adaptation, as the following picture indicates.

10G-40G migration solution 2

How to Get 100G Connectivity?
1). 10G to 100G Connection

Migrating from 10G to 100G still utilises 100G MTP/MPO breakout cable, the IEEE ratified the 100GBASE-SR10 (MTP/MPO interface) standard that uses 10 lanes at 10G SFP+ per lane over multiple fibre for a total of 20 fibres. Parallel optics 100GBASE-SR10 uses 20 out of 24 MTP/MPO interface fibres transmitting 10 duplex channels.

10G-100G migration solution 1

2). 100G to 100G Connection

100G connectivity can be achieved through ten 10G SFP+ transceivers. SFP+ transceiver operates on legacy duplex 10G lanes, thus taking full advantage of the existing network infrastructure. With a 24-fibre MTP/MPO trunk cable, of which 20 out of the 24 fibres are used to make duplex 10×10G transmission.

10G-100G migration solution 2

We can also get 100G to 100G connectivity via MTP/MPO assemblies: simply use the 24-fibre MTP/MPO interface trunk cable or 2×12-fibre MTP/MPO interface trunk cable. As shown in the following picture.

40G-100G migration solution 1


With the rapid increase in bandwidth consumption, the migration from 10G to 40/100G is inevitable. The economics of cost per port per 10Gbps is much more favorable for a 40GBASE-SR4 and 100GBASE-SR10 network. All the transceivers and cabling assemblies presented in the solutions are available in FS.COM. For more details, please visit www.fs.com or contact us via sales@fs.com.

Maintaining MPO/MTP Polarity

The local area network (LAN) campus and building backbones as well as data centre backbones are migrating to high cabled fibre counts to meet system bandwidth needs and provide the highest connectivity density. So manufacturers start to produce MPO/MTP high density cables. Then many network designers are turning to MPO/MTP trunk cable to get the highest connectivity density for an easy migration from 10G to 40/100G. To ensure reliable system performance as well as support ease of installation, maintenance and reconfiguration, MPO/MTP cables require unique polarity design. But how to maintain proper MPO/MTP polarity?

Optical fibre links typically require two fibres to make a complete circuit. Optical transceivers have a transmit side and receive side. In any installation, it is important to ensure that the optical transmitter at one end is connected to the optical receiver at the other. This matching of the transmit signal (Tx) to the receive equipment (Rx) at both ends of the fibre optic link is referred to as polarity. In traditional cabling systems, single fibre connectors such as LC, SC are used. So it’s easy to main the polarity as long as the A side of one connector pair matches to the B side of the other connector pair in any patch cord or permanent link. However, pre-terminated, high-density cabling systems based on MPO/MTP array connectivity require a new set of design rules and have their more complicated requirements for maintaining proper polarity. Before talking about maintaining MPO/MTP polarity method, we will first introduce MPO/MTP array connectors.

MPO/MTP Array Connectors

MPO/MTP array connectors terminate multiple fibres in a single high-density interface. 4-, 6-, 8-, 12-, 24-, 36- and 72-fibre connectors are available. But 12-fibre array connectors are the most common. MPO/MTP array connectors are employed in high-density permanent link installations and can be found in pre-terminated cassettes, trunk and hydra cable assemblies used extensively in data centres.

MPO/MTP array connectors are pin and socket connectors (as shown in the following picture), requiring a male side and a female side. Cassettes and hydra cable assemblies are typically manufactured with a Male (pinned) connector. Trunk cable assemblies typically support a Female (unpinned) connector. To ensure proper end-face orientation during mating process, connectors are keyed. When the key is at the bottom, it’s called key down. When the key is on the top, it’s called key up. Under the situation of key up, the fibre holes in the connector is numbered from left to right as P1, P2… There is a white dot on one side of the connector to identify where the P1 is.


Three Polarity Methods

The following will introduce three different methods to maintain polarity for systems using MPO/MTP optical connectivity. Defined by TIA/EIA-568-B.1-7, these methods include installation and polarity management practices, and provide guidance in the deployment of these types of fibre array links.

Method A

Method A employs Key Up to Key Down adapters to connect the array connectors. In this straight through configuration, Fibre 1 (P1) in the near end cassette mates to Fibre 1 (P1) in the trunk cable assembly. That is to say fibres at each end of the cable have the same position. Method A provides the simplest deployment for single-mode and multimode channels, and can easily support network extensions.


Method B

Method B uses Key Up to Key Up Adapters. The fibre circuit is completed by utilizing straight patch cords at the beginning and end of the link, and all of the array connectors are mated Key Up to Key Up. In this method, the fibre positions are reversed. Fibre 1 is mated with fibre 12, Fibre 2 mated with Fibre 11… To ensure proper transceiver operation with this configuration, one of the cassettes needs to be physically inverted internally so Fibre 12 is mated with Fibre 1 at the end of the link. This method is more complicated than method A to manage the polarity of links. As you should identify where the actual inversions need to occur. And it also requires two separate cassettes or special labeling and management of the cassettes on one end are flipped. What’s more, this method doesn’t easily accommodate angled polished (APC) single-mode connectors.


Method C

Method C uses Key Up to Key Down Adapters. This method uses straight patch cords and the same cassettes as in Method A. The difference is that the flip does not happen in the end patch cords but in the array cable itself. for example, Fibre 1 on one end is shifted to Fibre 2 at the other end of the cable. The Fibre 2 at one end is shifted to Fibre 1 at the opposite end etc. So it’s also complicated to properly manage the polarity of the links and to identify where the actual flipped array cord is placed in the link. Besides, it’s hard to extend the links. So this method is not suitable to be applied with emerging 40Gbps standards.



There are three methods to maintain MPO/MTP polarity. Network designers should evaluate each method before implementing to ensure the reliability, ease of installation, maintenance and reconfiguration as well as easy migration to higher data rates solutions like 40/100G Ethernet. It’s recommended that a method selected should better not be changed in an installation.