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Top 7 QSFPTEK 40G QSFP+ Optical Transceivers in 2023



Discover the top 7 QSFPTEK 40G QSFP+ optical transceivers and cables of 2023 for your 40Gb network. Find out which 40G QSFP is the best option for your enterprise core or distribution layer applications.

40G optical transceivers have a transmission rate of 40Gbps, its main packaging forms include CFP, QSFP+, and QSFP. QSFP+ 40Gb is one of the most frequently used fiber optical modules. The following lists the top seven 40G QSFP+ optics, including transceivers and high-speed DAC/AOC cables. I hope it will be helpful to you when you choose QSFP+ transceivers for your 40Gb network.

1. QSFP-40G-SR4 Optical Transceivers

The 40GBase-SR4-QSFP+ is often used with MPO/MTP streets in 40G data transmission. There are 4 full-duplex channels on this module and it transmits on four channels as well, the transmission speed is the same as LR4. The difference is that QSFP-40G-SR4-S optical modules are often used with multimode optical fibers in short-range applications.


Besides, the 40GBASE SR4 QSFP transceiver module with MPO connector can be applied in a 40Gb to 10Gb breakout cable connection. It’s common in the enterprise core layer and distribution layer applications. Please see the diagram below.

2. QSFP-40G-CSR4 Optical Transceivers

The QSFP-40G-CSR4 transceivers are similar to QSFP-40G-SR4 modules. Both are designed for use in 40 Gigabit Ethernet (40GbE) over short-range optical fiber applications. They are identical in four lanes, MTP/MPO connectors, and 850nm wavelength. The main difference is 40GBASE-CSR4 can used for longer reach. For example, the maximum transmission distance of Cisco QSFP-40G-CSR4 compatible 40G CSR4 transceivers by QSFPTEK is 400m over OM4 multimode fiber (MMF) and 300m over OM3 multimode fiber (MMF). However, Cisco QSFP-40G-SR4 QSFP+ can only reach 150m via OM4 MMF and 100m via OM3 MMF.


Also, QSFP CSR4 40G and SR4 transceivers are compliant with IEEE 10GBASE-SR specifications, and can also be applied to support 40G to 4x 10G breakout solutions.

3. QSFP-40G-LR4 Optical Transceivers

The QSFP-40G-LR4 is generally used together with LC single-mode fiber optic patch cords. The maximum transmission distance can reach 10km, and it has 4 data channels, which will transmit data at the same time. The QSFP-40G-LR4 optical module has the advantages of high density, low cost, high speed, large capacity, and low power consumption.


The working principle of the QSFP 40GBASE-LR4 optical module: The laser driver controls the arriving wavelength, and the optical signal passes through the multiplexer and is combined for transmission. When almost reaching the receiving end, these transmitted signals are demultiplexed into four channels with a transmission rate of 10Gbps, and then the PIN detector restores the data stream and then transmits the optical signal.


QSFP-40G-LR4 has a derivative product, QSFP-40G-LR4-S. What are the differences between QSFP-40G-LR4-S vs QSFP-40G-LR4? They are the same in appearance and specification. Both LR optics support 40Gb link lengths of up to 10km over single-mode fiber. The differences are the QSFP-40G-LR4-S supports 40GBASE Ethernet rate only and it does not support FCoE. So QSFP-40G-LR4-S is a cheaper option compared to QSFP-40G-LR4.

4. QSFP+-4x10G-LR Optical Transceivers 

As a highly integrated 4-channel optical module, the QSFP-4x10G-LR-S has the advantages of high port density and low cost. The 40G LR4 PSM optical module has the same working principle as the 40G SR4 QSFP+ optical module. The difference is that 40G PLR4 optical modules are often used to connect with single-mode ribbon fiber connectors, that is, parallel optical signals are sent in parallel through 8 single-mode fibers.


5. QSFP-40G-ER4 Optical Transceivers

The wavelength of the 40GBase-ER4 and the 40G LR4 optical module are the same. What differs them are Lasers and Receivers built-in.

First of all, the Tx end Lasers of 40G ER4 and LR4 vary in max cable distance although both of the two adopt DFB CWDM Lasers - the former can theoretically transmit 40km via G.652 optical cable whereas the latter can only transmit less than 10km over the same cable.


Second, the Rx end Receivers of 40G ER4 and LR4 are completely different - the former is a high-precision APD Receiver whereas the latter is a PIN Receiver. Therefore, 40G ER4 has better performance, but it costs much more than LR4.


Besides, 40G ER4 and 40G LR4 QSFP+ optical transceiver modules are quite different in application seniors - LR4 is usually used in data centers, and campus networks, while ER4 is often used in metropolitan area networks and small data center interconnections.

Model name



















LC UPC Duplex



10km (OS2)





40km (OS2)


LC UPC Duplex

6. 40G QSFP+ DAC Cables

There are two types of 40G QSFP DAC cable, one is 40G QSFP to QSFP DAC, which is composed of two 40G QSFP+ optical transceivers and a copper cable. And the other is a 40Gbe to 4x10Gbe QSFP+ breakout DAC cable, also referred to as QSFP+ to SFP+ breakout DAC cable, which is composed of one 40G QSFP module at one end and four 10G SFP+ modules at the other end. These QSFP+ breakout cables connect to a 40G QSFP+ connector of a switch on one end and to four 10G SFP+ connectors of a switch on the other end.

Advantages of DAC:

1. Low cost. Reducing the impact of dust and other pollutants on the cable. Easy to maintain. 

2. Low price. The inside of the high-speed cable is made of copper core, which has a good heat dissipation effect, energy-saving and environmental protection;

3. low power consumption. Less than 2W. That’s a significant advantage in data center applications.

7. 40G QSFP+ AOC Active Optical Cables

QSFP AOC active optical cable is an efficient integrated optical cable component product designed for short-distance multi-channel data communication and interconnection applications. There are 4 data channels in each signal direction, and the rate of each channel is 10Gbps.


Advantages of AOC:

1. Larger bandwidth: No equipment upgrade is required, with a throughput of up to 40Gbps.

2. Lightweight: much lighter than high-speed cables.

3. Low electromagnetic interference: Since optical fiber is a kind of dielectric, it is not easy to be affected by electromagnetic interference. 

4. High transmission rate, long transmission distance, low energy consumption, easy to use, etc.



QSFPTEK is an optical fiber communication brand with R&D integration. It also manufactures and sells on one platform. 40G QSFP+ transceivers (40GBASE-SR4, 40GBASE-LR4, 40GBASE-ER4, 40GBASE-ZR4), 40G QSFP+ DAC cable, 40G QSFP+ DAC breakout cable, 40G QSFP+ AOC cable, 40G QSFP+ AOC breakout cable are all available here. Each optic has been thoroughly tested on host devices to ensure compatibility before delivering to users.



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