Selection Guide to 40G QSFP+ Transceivers and Cables

In order to better accommodate the increasing demands that data center growth puts on the network, various bandwidth-delivering fiber optical products have been designed and developed by telecommunication equipment manufacturers. Among this fiber optical equipment, transceiver modules, one of the most critical components for establishing fiber links, have attracted more and more attention for their unique and sophisticated designs. There is a wide range of pluggable transceivers modules in the market, supporting several form factors, like SFP, SFP+, QSFP+, with performance data rate from 1Gbps to, to 10Gbps, to 40Gbps, etc. This text focuses on 40G QSFP+ transceiver modules and their cabling options, guiding you to select the right 40G QSFP+ transceiver and cable type for your networking project.

40G QSFP+ Transceiver Selection Guide

The Quad Small Form-factor Pluggable (QSFP) is a compact, hot-pluggable transceiver used for data communications applications in 40Gigabit per second links. QSFP connectors provide four channels of data in one pluggable interface. Each channel is capable of transferring data at 10Gb/s and supports a total of 40Gb/s as specified for QSFP+. Listed below are two commonly-used QSFP+ types: 40GBASE-SR4, 40GBASE-SR-BiDi, and 40GBASE-ER4.

  • 40GBASE-SR4

40GBASE-SR4 is specified to work through multi-mode fiber (MMF), able to achieve link lengths of 100m and 150m respectively, on laser-optimized OM3 and OM4. It establishes high-bandwidth 40G optical links over 12-fiber parallel fiber terminated with MPO/MTP multi-fiber female connectors. Besides, this 40GBASE-SR4 standard can also be used in a 4x10G mode for interoperability with 10GBASE-SR interfaces, with distances up to 100m and 150m on OM3 and OM4, respectively. Fibertore listed 40GBASE-SR4 products include Intel E40GQSFPSR, Cisco QSFP-40G-SR4, Mellanox MC2210411-SR4, and so on. All are tested for compatibility with these major brands.

Selection Guide to 40G QSFP+ Transceivers and Cables 1

  • 40GBASE-SR-BiDi

QSFP 40-Gbps bidirectional (BiDi) transceiver is a pluggable optical transceiver with a duplex LC connector interface for short-reach data communication and interconnect applications using MMF. Each QSFP 40-Gbps BiDi transceiver consists of two 20-Gbps transmit and receive channels in the 832-918nm wavelength range, enabling an aggregated 40-Gbps link over a two-strand MMF connection. By supporting link lengths of 100m and 150m on laser-optimized OM3 and OM4 respectively, QSFP 40-Gbps BiDi transceiver offers customers a compelling solution that enables reuse of their existing 10 Gigabit duplex MMF infrastructure for migration to 40GbE connectivity.

  • 40GBASE-ER4

40GBASE-ER4 is standardized to operate over SMF, permitting link lengths up to 40km with duplex LC connectors. The 40GE or OTU3 signal is carried over four wavelengths in the 1310nm range. Multiplexing and demultiplexing of the four wavelengths are managed within the device. QSFP-40G-ER4, a Cisco 40GBASE-ER4 product, is just capable of accomplishing 40km link length over G.652 SMF.

40G QSFP+ Cable Selection Guide

40G QSFP+ cabling options generally include the following four flavors: MPO/MTP fiber patch cable, QSFP to QSFP copper direct attach cables (DACs), QSFP to QSFP active optical cables (AOCs), QSFP to four SFP+ breakout cables. The following passages will focus on the latter three options.

  • QSFP to QSFP Copper DACs/AOCs

Both QSFP to QSFP copper DACs and QSFP to QSFP AOCs are designed for very short distances, serving a flexible solution to connect within racks and across adjacent racks. Compared with copper DACs, AOCs are much thinner and lighter, meaning the easier cabling. Additionally, AOCs enable efficient system airflow and have no EMI issues, which is critical in high-density racks. QSFP to QSFP copper DACs is available in length of 1, 3, 5, 7, and 10m, while QSFP to QSFP AOCs allows the maximum link length of 15m.

  • QSFP to Four SFP+ Breakout Cables

QSFP to four SFP+ breakout cables are available in two kinds: QSFP to four SFP+ copper breakout cables, and QSFP to four SFP+ active optical breakout cables. In a QSFP to four SFP+ breakout cabling assembly, a 40G QSFP port of a switch is connected to the cable on one end and four 10G SFP+ ports of a switch on the other end, free from upgrading the entire data center or storage array. Each QSFP-SFP+ splitter cable features a single QSFP connector (SFF-8436) rated for 40-Gb/s on one end and (4) SFP+ connectors (SFF-8431), each rated for 10-Gb/s, on the other.

QSFP to Four SFP+ breakout cables are currently available in 1, 2, 3, 5, 7, and 10m, functioning as a great cost-effective interconnect solution to IT professionals by providing much needed space for data centers and low costs.


In a word, 40G QSFP+ transceivers and cables offer multiple connectivity options with the media type (DAC, AOC, SMF, and MMF) in data centers. For some data center networks, the main connectivity problems are related to low-quality and incompatible modules. Fiberstore just helps you to clear off these problems. Here in Fiberstore, its 40G QSFP+ modules have been vigorously tested, and are ensured with high quality to work in compatibility with major brands. You can buy them with no concerns about quality or performance.


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