Choosing the 40G Transceivers

With the economics-driven growth of global regional and local fiber communication network over the past few decades, the IEEE 802.3 ba 40Gb/s Ethernet standard was published in June, 2010. In order to meet the data transmission needs in the market, a high-performance and flexible implementation of the IEEE 802.32012 for 40Gbps Ethernet - 40GBase optical transceivers are developed and widely used. The 40GBase optical networking equipment transfers data at a rate of 40 gigabits per second over Ethernet.

40GBase optical transceivers, compliant to the IEEE standards mainly include CFP and QSFP (quad small form-factor pluggable). Today, let’s mainly discuss on how to choose the 40G QSFP transceiver. As the 40-Gigabit QSFP transceivers are used to interface networking hardware to a fiber optic cable, the choice of them depends on many factors, like the media system, the connector type, transmission distance, wavelength, etc. Thus we should consider all these factors comprehensively before we choose the 40G QSFP transceivers.

Choose the right transceivers according to the transport media, namely the fiber type. According to the IEEE 802.3 ba 40Gb/s Ethernet standard, there are three types of transceivers used respectively in three types of transport media: copper, single mode fiber (SMF) and multimode fiber (MMF).

• Copper: 40GBASE-CR4 is a direct attach cable segment with the QSFP+ modules attached to each end of the cable. It reaches 40 Gb/s Ethernet over four short-range twinaxial copper cables bundled as a single cable over a standard pair of G.652 single-mode fiber. For example, Juniper EX-QSFP-40GE-DAC-50CM compatible QSFP+ to QSFP+ copper direct attach cable is suitable for very short distances and offers a very cost-effective way to establish a 40-Gigabit link between QSFP ports of Juniper switches within racks and across adjacent racks.
• SMF: 40GBASE-LR4 transceiver reaches 40 Gb/s Ethernet over four wavelengths carried by a singlemode fiber optic cable.
• MMF: 40GBASE-SR4 transceiver reaches 40 Gb/s Ethernet over four short-range multimode fiber optic cables.

Choose the right transceivers which are compliant with the proper connectors. The connectors widely-used mainly have following types: Duplex LC connector, MPO connector, and MTP connector (a high performance MPO connector). For instance, Cisco QSFP-40GBD-SR transceiver is compliant with the Duplex LC connector, while Arista QSFP-40G-PLR4 transceiver is compliant with the MPO connector.

When we choose the ideal transceivers, we must consider the transmission distance and the reach requirements we need in reality. The most common types of transceivers divided by its transmission distance can reach up to 100m, 150m, 300m, 400m, 1km, 2km, 10km, 40km, etc. For example, Cisco QSFP-40G-CSR4 compatible QSFP+ transceiver provided by Fiberstore supports link lengths of 82m, 300m and 400m, respectively on OM2, OM3 and OM4 multimode fibers at a wavelength of 850nm. And some others, like QSFP-40G-ER4 transceiver which supports link lengths of 40km on single-mode fiber cable is designed to use in long distance transmission.

The wavelength the transceivers operate with is an important factor in choosing the proper transceivers. For instance, QSFP-40G-LX4 transceiver converts 4 inputs channels (1271nm, 1291nm,1311nm, 1331nm) of 10Gb/s electrical data to 4 CWDM optical signals, and multiplexes them into a single channel for 40Gb/s optical transmission. While some other transceivers like QSFP-40GBD-SR consists of two 20-Gbps transmit and receive channels in the 832-918 nm wavelength range.

Fiberstore provides various types of 40G QSFP transceivers including single-mode and multi-mode with different channels and wavelengths. In order to achieve a fast and successful selection of the 40G QSFP transceivers, we should consider all the above-mentioned factors comprehensively.