Cabling Solutions for 40G Short Reach QSFP+ Transceivers

40G parallel optical transceivers use four 10G channels to transmit and four 10G channels to receive signals over a 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. 40gb QSFP+ is the dominant transceiver type and popular choice for 40 Gigabit Ethernet applications. Among all those QSFP+ optics, short reach QSFP+ transceivers are commonly used. This article will introduce cabling solutions for 40G short reach QSFP+ transceivers.

In 2010, 40GBASE-SR4 parallel optics solution for MMF was released by IEEE standard 802.3ba as one of several 40G based solutions. Later, another solution 40GBASE-CSR4 was released. 40GBASE-CSR4 is similar to 40GBASE-SR4 but it extends the distance capabilities. These two multi-mode transceivers can also support 4x10G modes. This part will tell details about these two short reach 40G parallel optical QSFP+ transceivers.

40GBASE-SR4 QSFP+: 40GBASE-SR4 QSFP+ transceiver enables 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 OM3 and OM4 multimode fibers respectively. 40GBASE-SR4 QSFP+ transceiver 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+: 40GBASE-CSR4 QSFP+ transceiver can be used for native 40G optical links over 12-fiber parallel cables with MPO/MTP 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 OM3 and OM4 multimode parallel fibers respectively.

To connect a parallel optics 40GbE short reach transceiver to another short reach 40GbE transceiver, a Type-B female MTP/MPO to female MTP/MPO cable is required. The following picture shows two 40GBASE-SR4 QSFP+ transceivers being connected with a female MTP cable. The fiber position (from 1 to 12) is reverse on the ends of the assembly. This reverse fiber positing allows signals 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 to this, there are several other cabling solutions for parallel optics 40G short reach connectivity. Solution one, in the interconnect structured cabling system, MTP trunk cables will be deployed by placing them in cable trays without the fear of them being crushed.

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

Solution three, this approach uses 40G channel interconnect structured with conversion devices: 2×3 or 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.

With the increasing demand for high-bandwidth applications such as cloud computing, server virtualization and fabric consolidation within data centers, the trend for faster data transfer rates like 40G and 100G is relentless. There are various types of 40GbE transceivers, MPO/MTP cables like MPO/MTP trunk cable and MPO/MTP harness cable, MPO/MTP cassette and other assemblies for your 40G network connectivity. You just need to make sure that you choose the right one.