40GBASE-SR4 QSFP+ Transceiver Connection Cabling
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40GBASE-SR4 QSFP+ Transceiver Connection Cabling

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As we all know, the standard specifies MPO as a connector to the 40GBASE-SR4 QSFP+ transceiver. To connect a QSFP+ to QSFP+, we usually use a MTP 12-fiber trunk cable. In the 40GBASE-SR transmission, there are eight fibers associated with the channel—four fibers for the TX signal and four fibers for the RX signal. Therefore only 8 of the 12 fibers are used, where the remaining four are not used, and can optionally be not present in the cable. So we can also choose a MTP 8-fiber trunk cable for connectivity. Besides this, there are a number of other factors also needed to be considered when to choose a right MTP trunk cable for 40GBASE-SR4 QSFP+ connectivity. This article explains 40GBASE-SR4 QSFP+ to 40GBASE-SR4 QSFP+ cabling selections.

40G direct connection with MTP trunk cable

Figure 1: 40G direct connection with MTP trunk cable.

Use Single-mode or Multimode MTP Trunk Cable?

In the market, both single-mode and multimode MTP trunk cable are available. Which one should I use? According to 40GBASE-SR4 standards, 40GBASE-SR4 QSFP+ transceiver supports link lengths of 100 meters and 150 meters, respectively, on laser-optimized OM3 and OM4 multimode fibers. Therefore, to connect a 40GBASE-SR4 QSFP+ to 40GBASE-SR4 QSFP+, we should choose OM3 or OM4 multimode MTP trunk cables. If you want to achieve a relatively longer transmission distance, OM4 MTP Trunk cable is more suitable for you.

MTP Trunk Cable Polarity Selection: A, B or C?

In terms of MTP trunk cable, there are three kinds of polarity options (A, B and C). Which one to choose? In fact, according to the IEEE 40GBASE-SR4 specifications, we must select a type B MTP 8-fiber or MTP 12-fiber trunk cable. The picture below shows the working principle of type B MTP 12-fiber trunk cable. The type B trunk cable has opposing connectors with both keys oriented facing up, however the fiber positions are reversed at each end i.e. the fiber at position 1 at one end is connected to position 12 in the connector at the opposing end.

Type B MTP 12-fiber trunk cable

Figure 2: Type B MTP 12-fiber trunk cable.

Choose Male or Female MTP Trunk Cable?

In terms of a MPO connector, it is divided into male and female types. They ensure that the adapter holds the connector with the correct ends aligned with each other. A MPO trunk cable usually has two MPO connector on each side. Therefore, MTP trunk cables are available in male-male and female-female two versions. According to IEEE standards, MPO optics in a 40GBASE-SR4 transceiver are always male connectors, and therefore will always accept female MPO connectors. So if we want to connect a 40GBASE-SR4 QSFP+ to a 40GBASE-SR4 QSFP+ successfully, we must choose a female-female MTP trunk cable.

Male MPO/MTP connector and female MPO/MTP connector

Figure 3: Male MPO/MTP connector and female MPO/MTP connector.

40GBASE-SR4 QSFP+ Transceiver Interconnection MTP Trunk Cabling Solutions
Original Part Number Description
QSFP-40G-SR4 Cisco QSFP-40G-SR4 Compatible 40GBASE-SR4 QSFP+ Transceiver (MMF, 850nm, 150m, MTP/MPO, DOM)
QFX-QSFP-40G-SR4 Juniper QFX-QSFP-40G-SR4 Compatible 40GBASE-SR4 QSFP+ Transceiver (MMF, 850nm, 150m, MTP/MPO, DOM)
JG325B HP JG325B Compatible 40GBASE-SR4 QSFP+ Transceiver (MMF, 850nm, 150m, MPO, DOM)
40GBASE-SR4 QSFP+ to 40GBASE-SR4 QSFP+ MTP Trunk Cables
Product ID Description
30977 Customized 8-144 Fibers OM3 Multimode 12 Strands MTP Trunk Cable 3.0mm
30962 Customized 8-144 Fibers OM4 Multimode 12 Strands MTP Trunk Cable 3.0mm
44110 1m (3ft) MTP Female to MTP Female 12 Fibers OM3 50/125 Multimode Trunk Cable, Type B, Elite, LSZH, Magenta
43934 1m (3ft) MTP Female to MTP Female 12 Fibers OM4 50/125 Multimode Trunk Cable, Type B, Elite, LSZH, Magenta

Conclusion

In summary, if we want to complete a connection between two 40GBASE-SR4 QSFP+ transceivers, we can choose MTP 8-fiber or MTP 12-fiber trunk cables. Cable must be either OM3 or OM4 type. Besides, only a type B female – female MTP trunk cable can satisfy your needs. Fiberstore provides wide brand compatible 40GBASE-SR4 QSFP+ transceivers and all kinds of MTP trunk cables. Each fiber optic transceiver has been tested to ensure its compatibility and interoperability. Please rest assured to buy. For more information or quotation, please contact us via sales@fs.com.

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