Complete Guide to 40G QSFP+ Optical Transceivers and Cables

Four Technologies

QSFP stands for Quad Small Form-factor Pluggable. 40G QSFP+ connectivity is an evolution of the 10G SFP+ connectivity. Indeed, the “Quad” of QSFP+ takes its meaning from the fact that 40GBase QSFP+ provides four channels of 10G.

Four different technologies can be found among the 40GBase QSFP+  family: Multi-mode TransceiversSingle-mode TransceiversDirect Attached Cables and Active Optical Cables. Of course, each technology has its advantages and inconveniences. In this article, we are going to introduce each technology to help you select the most suitable 40G QSFP+ connectivity for your network.

Multi-mode Transceivers

Multi-mode transceivers are the low cost transceivers.  QSFP+ SR4/eSR4 use more expensive non-standard MPO connectors which cancel out some of the cost savings of the transceiver. This approach is similar to using AOC cables, but here it is possible to use structured cabling.


The 40GBase QSFP+ SR4 transceiver supports connections of up to 100 meters over multi-mode fiber and uses MPO connectors. The wavelength is 850nm.

40G QSFP+ eSR4

The 40GBase QSFP+ eSR4 is similar to QSFP+ SR4 transceiver, it also uses MPO connectors and 850nm wavelength but it supports connections of up to 300 meters over multi mode fiber.


The 40GBase QSFP+ LX4 transceiver can be used over multi-mode and single-mode. Over multi-mode it can reach up to 150 meters with OM3 cable. The differences with the SR4 and eSRA are the 1310nm wavelength and the standard LC connectors.

40G QSFP+ Bidi

The 40GBase QSFP+ Bidi has two 20G channels that supports connections up to 100 meters on OM3 and up to 150 meters on OM4. It uses LC Duplex connector and the wavelength is 850nm.

Single-mode Transceivers

Single-Mode transceivers are more expensive than multi-mode transceivers but they allow to reach longer distance and most of them are using standard LC connectors.


The 40GBase QSFP+ LX4 transceiver can be used over multi-mode and single-mode. Over single-mode it can reach up to 2km. It uses 1310nm wavelength and LC connectors.


The 40GBase QSFP+ LR4 transceiver supports connections up to 10 km over single-mode fiber and uses standard LC connectors. The wavelength is 1310nm.


The 40GBase QSFP+ PSM4 transceiver supports connections up to 10 km over single-mode fiber and uses non-standard MPO connectors. The wavelength is 1310nm.


The 40GBase QSFP+ ER4 transceiver supports connections up to 40 km over single-mode fiber and uses standard LC connectors. The wavelength is 1310nm.

Direct Attached Cables (DAC)

Direct Attached Cables are a very common method for very short-range distance because of the their low-cost. Indeed, they are the cheapest solution for connecting 40G equipment. In addition, it is a one part product instead of the usually three part solution ( two transceivers and a cable), which reduces the problems associated with dirty connectors. DAC also consume less power compared to Active Optical Cables (AOC).

There are two types of DAC, the passive copper cable for distance from 0 to 5 meters and active copper cable for distance from 5 to 15 meters.

QSFP+ to 4 x 10G SFP+ fanout DAC

Active Optical Cables (AOC)

Active Optical Cables are comparable to using transceivers and separated cables. They can reach longer distance than DAC, up to 100 meters. They also are lighter and smaller than DAC.

QSFP+ to 4 x 10G SFP+ fanout AOC


Technology Standard Optech Part Number Features
Multi-Mode Transceivers 40G QSFP+ SR4 OPCS-MX1-85-CB 850nm, 100 meters, MPO
40G QSFP+ eSR4 OPCS-MX3-85-CB 850nm, 300 meters, MPO
40G QSFP+ LX4  OPCS-X02-13-CB 1310nm, 150 meters, LC
40G QSFP+ Bidi OPCS-X02-13-CB 850nm, 100/150m, LC
Single-Mode Transceivers 40G QSFP+ LX4 OPCS-X02-13-CB 1310nm, 2km, LC
40G QSFP+ LR4 OPCS-S10-13-CB 1310nm, 10km, LC
40G QSFP+ PSM4 OPCS-S10-13-CBS 1310nm, 10km, MPO
40G QSFP+ ER4 OPCS-S40-13-CB 1310nm, 40km, LC
Direct Attached Cables 40G QSFP+ to QSFP+ DAC OPQSFP-T-xx-P xx= 0,5 to 7 meters
40G QSFP+ to 4 SFP+ DAC OPQSFP-T-xx-P/SFPP/4 xx= 0,5 to 7 meters
Active Optical Cables 40G QSFP+ to QSFP+ AOC OPQSFP-F-xx-AKA xx= 1 to 100 meters
40G QSFP+ to 4 SFP+ AOC OPQSFP-F-xx-A/SFPP/4 xx= 1 to 100 meters

Optech products are compatible with all major switches and servers brands. You can check all the compatible lists here.

About Optech

Optech Technology Co. Ltd was founded in 2001 in Taipei, Taiwan. The company was created with a sole purpose, to provide a wide and high quality portfolio of optical products to a very demanding and fast evolving market.

To respond to the permanent increase of IP traffic, Optech portfolio is constantly growing. Since the beginning, the company has always been up to date with the latest innovations on the market. Today, we are proud to deliver a large selection of 25G SFP28, 40G QSFP+, 100G QSFP28 and 400G QSFP-DD optical transceivers and cables.

Optech has a large portfolio of products which include optical transceiversdirect attach cablesactive optical cablesloopback transceiversmedia converters and fiber patch cords.

Through its large selection of optical products, that have a range of data speed from 155 Mbps to 400 Gbps and reach distances up to 120km, Optech products are suitable for various industries such as telecom, data centers as well as public and private networks.

Optech also has a strong experience as an OEM supplier. We put our expertise and knowledge at the service of your brand.

To ensure the quality and the compatibility of our products, every product is carefully tested before delivery to our customers. In addition, Optech obtained several certifications such as UL, TUV Rheinland, ISO9001 and ISO14001 certification. All our optical transceivers are MSA and RoHS compliant.

At Optech, we value each and every customer. We know every demand is unique. For this reason, our team of experts is glad to answer all our customers’ specific demands.

Just like data, Optech has no boundaries and will optimize your network all over the world.

For more information you can visit or contact us at

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