Cabling Connectivity for 40G Short Reach Transceivers
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Cabling Connectivity for 40G Short Reach Transceivers

Posted on by FS.COM

Originally the Ethernet standard has relied on duplex fiber cabling with each channel using one fiber to transmit and the other to receive. Later, the 802.3ab standard requires multiple lanes of traffic per channel. So some of 40 Gigabit transceivers uses parallel optic transmission technology which spatially multiplexes or divides a high-data-rate signal among several fibers that are simultaneously transmitted and received. This article will introduce cabling connectivity for 40G short reach parallel optic transceivers.

40G Short Reach Transceivers

40G parallel optical transceivers use four 10G channels to transmit and four 10G channels to receive over one 12-fiber assembly. The middle four fibers remain unused, or dark. Each fiber either transmits (Tx) or receives (Rx) 10G traffic at a single wavelength. The QSFP+ transceiver is the dominant transceiver used for 40 Gigabit Ethernet applications. In 2010, 40GBASE-SR4 parallel optics solution for MMF was released by IEEE standard 802.3ba as one of several 40G based solutions. Since then, some other engineered solutions have been released, including 40GBASE-CSR4, which is similar to 40GBASE-SR4 but extends the distance capabilities. The following table tells more details about these two short  reach 40G parallel optical transceivers.

Part Number Image Description

The 40GBASE-SR4 QSFP modules primarily enable high-bandwidth 40G optical links over 12-fiber parallel fiber terminated with MPO/MTP multi-fiber female connectors. It can support link lengths of 100 meters and 150 meters over laser-optimized OM3 and OM4 multimode fibers respectively. It can also be used to connect with four 10GBASE-SR optical interfaces using an 8-fiber MTP to 4 duplex LC cable.


40GBASE-CSR4 QSFP modules can be used for native 40G optical links over 12-fiber parallel cables with MPO/MTP female connectors or in a 4x10G mode with parallel to duplex fiber breakout cables for connectivity to four 10GBASE-SR interfaces. It can extend the reach of 40GBASE-SR4 interface to 300 and 400 meters over laser-optimized OM3 and OM4 multimode parallel fibers.

As the above mentioned, 40G parallel optic transceivers transmit over four fibers and receive transmissions over four fibers, with four lines in each direction. This is to allow for easier development of 40G,  reusing 10G components. As a side result, these two multi-mode transceivers can also support 4x10G modes.  With a fiber, the source 40G port running in 4x10G mode can be connected to 4 unique 10G destinations.

Cabling Solutions for 40G Short Reach Transceivers

To connect a parallel optics 40 Gigabit Ethernet transceiver to another 40 Gigabit Ethernet transceiver, a Type-B female MPO/MTP to female MPO/MTP cable is required. The following figure shows two QSFP+ transceivers being connected with an MTP female cable. The fiber position (from 1 to 12) is reverse on the ends of the assembly. This reverse fiber positing allows the signal to flow from transmission on one end of the link to reception on the other end. This type of direct connectivity is only suggested for short distances within a given row of racks/cabinets. It has less robustness (less tensile strength, less crush and impact resistance, etc.) than a distribution-style cable, which would be used for structured cabling trunks.


In addition, there are some other cabling solutions for parallel optics 40G connectivity shown as following.

First solution, in the interconnect structured cabling system, MTP Trunk cables will be deployed by placing them in cable trays without the fear of the trunk cable being crushed.


Second solution, with 2×12 to 3×8 or 1×24 to 3×8 harness assembly, 100% fiber utilization will save the cost of fiber utilization in the structure cabling. And it also saves the cost of deploying labor and materials. Make sure that each MTP connector is plugged into a port.



Third solution, this approach uses 40G channel interconnect structured with conversion devices: 2×3 &1×3 modules. It can utilize 100% of the installed fiber as harnesses. It is easily accomplished by using Type-B non-pinned MTP to non-pinned MTP jumpers.




As the demand for high-bandwidth applications such as server virtualization and cloud computing, fabric consolidation within the data center is increasing, the trend of faster data transfer rates like 40G is relentless. Fiberstore provides various types of 40GbE transceivers, MPO/MTP trunk cable, MPO/MTP harness cable, MPO/MTP cassette and other assemblies for your 40G network connectivity. Each Fiberstore transceiver have been tested to proven its performance and compatibility. If you need any service, please contact us via

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