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fiber optics1
Data Centre

Type-B Polarity MTP Cable User Guide

Type-B Polarity MTP Cable User Guide

FS Official 2016-08-09

As demand grows for higher speed, large data centres being built today have begun to make preparations for 40G/100G transmission. MTP cables, with great performance and high speed, have become the main component in data centres.

In today's data centres, MTP cables, like 8-fibre or 12-fibre MTP cable, are frequently used to establish an optical path between switch tiers. Different from common fibre patch cords, one MTP cable has multiple fibres inside, which leads to more complex in the polarity management. Because the MTP connector terminates multiple fibres in a single high-density interface. And there are different fibre positions. To match these fibre position, TIA standards define three types of polarity MTP cables: type-A, type-B and type-C. Different types polarity cables may have different applications. In this tutorial, we will mainly introduce the type-B polarity MTP cables and its applications. For completed polarity guide of FS products, you can refer to our white paper Understanding Fibre Polarity.

Overview: Get Close to Type-B Polarity MTP Cable

The type-B polarity MTP fibre uses key up connector on both ends of the cable. Often referred to as a 40G MTP cable, the type-B MTP cable is the second standard for polarity, and extremely versatile. This cable assembly can be used to plug directly between your 40G QSFP+ optic transceivers, so it is commonly referred to as a QSFP/QSFP+ cable or direct attach 40GBASE-SR4. As you can see in the diagram, this cable has a “flipped” polarity and will result in a Pin 1 to Pin 12 relationship. This is extremely useful because 40G optics utilize parallel optics, meaning instead of alternating Tx and Rx in a duplex pattern, the port will look like the following diagram.

mtp type-b cable Figure 1: Type-B polarity MTP cable

Categories: Diverse Types to Meet Different Challenges

In today’s fibre optic networks, especially in data centres, MTP trunk cable and MTP-LC harness cable are two most common types used. Besides, MTP connector is pin and socket connectors, which require a male side and a female side. Therefore, in terms of MTP trunk cable, there are female-female, female-male and male-male three types. In addition, when connecting two parallel optics 40G SR4 QSFP+ transceivers, only a female to female type-B MTP cable should be used. For MTP-LC harness cable, female MTP-LC harness cable and male MTP-LC harness cable are available.

mtp type-b cable Figure 2: Type-B polarity MTP cable types

Applications: One Cable, More Possibilities

MTP cables are designed for higher bandwidth applications such as 40GbE and 100GbE. Due to the special structure, a female MTP cable is often required to mate a male MTP cable. Male guide pins fit into the female holes to ensure precise fibre alignment. Attempting to mate two female connectors or male connectors will cause light loss or damage the fibre connectors. The following examples mainly explore applications of female type-B polarity MTP cables.

Direct Connection: Female to Female Type-B Polarity Trunk Cable

Except for the parallel 40G optical transmission mentioned above, female to female type-B trunk cable also can be used direct switch to switch connectivity with no patch panels. The following figure shows two Cisco 40G transceivers connected by a 12-fibre MTP female cable directly.

mtp type-b trunk cable Figure 3: Female to female 12-fibre type-B MTP cable in 40G connection

With a MTP adapter, type-B MTP polarity trunk cable can be used for connecting a patch panel and QSFP+ SR4 transceiver.

Direct Connection: Female MTP to LC Type-B Polarity MTP Harness Cable

How to breakout 40G link into four 10G links for a different purpose? A female MTP-4LC type-B harness cable can solve this problem easily. The following figure shows the four 10GBASE-LR SFP+ transceivers interconnect with one 40GBASE-LR QSFP+ transceiver by one female MTP-4LC harness cable directly.

type-b mtp-lc harness cable Figure 4: 8-fibre type-B MTP-LC breakout cable in 40G connection

Interconnections: Type-B MTP Trunk Cable and Type-B MTP Harness Cable

Type-B MTP trunk cable and harness cable can be used together to achieve high performance fibre networking. Figure 5 shows the interconnect of 10GBASE-LR SFP+ optics transceivers connected by type-B MTP trunk cable and harness cable. It is an ideal solution to link two Cisco switches in the data centre for high speed fibre optic transmission.

mtp type-b trunk cable and harness cableFigure 5: type-B MTP trunk cable and harness cable in 10G interconnection


The biggest market for 40GbE and 100GbE is in data centres for interconnection links with servers and storage area networks. Optimal for 40G and 100G application, MTP cables become more and more popular than before in data centres. To simplify the complex networking cabling, FS polarity management solution for base-8, base-12 and base-24 MTP/MPO cabling allow data centre managers to effectively migrate to 40/100G.

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