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.

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.

Cabling Solutions for Short Reach QSFP+ Transceivers

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.

Conclusion

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.

Comparison Between Twisted Pair Cable, Coaxial Cable and Fiber Optic Cable

A communication system usually uses a wire or cable to connect transmitting and receiving devices. Currently, there are mainly three cable types deployed in communication systems, which are twisted pair cables, coaxial cables and fiber optic cables. Each type has been widely utilized in communication networks. What’s the difference between these three kinds of cables? This article will make a comparison between them.

Twisted Pair Cables

Twisted pair cable consists of a pair of insulated wires twisted together, which has been adapted in the field of telecommunication for a long time. With the cable twisting together, it helps to reduce noise from outside sources and crosstalk on multi-pair cables. Basically, twisted pair cable can be divided into two types: unshielded twisted-pair (UTP) cable and shielded twisted-pair (STP) cable. UTP cable, such as data communication cables and normal telephone cables, serves as the most commonly used cable type with merely two insulated wires twisted together. STP cable distinguishes itself from UTP cable in that it includes a foil jacket which helps to prevent crosstalk and noise from outside source. STP cable is typically used to eliminate inductive and capacitive coupling, and it can be applied between equipment, racks and buildings. The table below shows several different types of twisted pair cables.

Coaxial Cables

Coaxial cable is a type of high-frequency transmission cable which contains a single solid-copper core. A coaxial cable has over 80 times the transmission capability of the twisted-pair cable. Coaxial cables are commonly used to deliver television signals and to connect computers in a network as well. There are mainly two kinds of coaxial cables: 75 Ohm coaxial cable and 50 Ohm coaxial cable.

75 Ohm coaxial cable

The primary use of 75 Ohm coaxial cables is to transmit video signals. One typical application of 75 Ohm coaxial cable is to transmit television signals over cable, which is why sometimes it is called signal feed cables. The most common connector type used in this application is a Type F. Another application is video signals between components, such as DVD players, VCRs or receivers commonly known as audio/video (A/V) cables. In this case, BNC and RCA connectors are often found. In both applications, RG59 with both solid center conductor (RG59B/U) and stranded center conductor (RG59A/U) as well as RG6 are common choices.

50 Ohm coaxial cable

The primary use of 50 Ohm coaxial cables is the transmission of data signals in a two-way communication system. Several common applications for 50 Ohm coaxial cables are computer ethernet backbones, wireless antenna feed cables, GPS (Global Positioning Satellite) antenna feed cables and cell phone systems.

Fiber Optic Cables

Computing and data communications are fast-developing technologies. To meet the transmission of ever-increasing data rates, there comes a new generation of transmission medium, which is fiber optic cable. Fiber optic cable transmits information using beams of light at light speed rather than pulses of electricity. It refers to the complete assembly of optical fiber. A fiber optic cable can contain one or more strands of optical fiber to transmit data. Each strand of optical fiber is individually coated by plastic layers and contained in a protective tube. Fiber optic cable transmits data as pulses of light go through tiny tubes of glass, the transmission capacity of which is 26,000 times higher than that of twisted-pair cable. When comparing with coaxial cables, fiber optic cables are lighter and more reliable for transmitting data.

Two widely used types of fiber optic cables are single-mode fiber optic cables and multimode fiber optic cables. A single-mode optical fiber has a small core, and only allows one mode of light to propagate at a time. It is generally adapted to high speed and long-distance applications. A multimode optical fiber has a larger core diameter than a single-mode optical fiber and it is designed to carry multiple light rays, or modes at the same time. It is mostly used for communication over short distances because of its high capacity and reliability, serving as a backbone applications in buildings. And there are many connector types for fiber optic cable, such as LC, SC, ST or FC connector. You can choose fiber optic cables terminated at both ends with the same or different connector types to connect different devices, like LC SC fiber patch cable, LC to LC fiber patch cable. There are both single-mode and multimode, and simplx and duplex fiber optic patch cables for your options, such as LC to LC multimode duplex fiber optic patch cable, LC to SC duplex single-mode fiber optic patch cable, or LC LC multimode fiber patch cord.

Conclusion

As the technology in the field of network is developing rapidly, fiber optic cables seem to become the trend to meet the increasing demand of data rates in the market. However, whether to choose twisted pair cables, coaxial cables or fiber optic cables still depends heavily on applications. And other factors, such as the cost, transmission distance and performance, also need to be taken into consideration when making a choice.