Currently, there are few kinds of transmission solutions are used for 40GbE. Most of the time people use 40GbE, 40G QSPF or 4 x 10GE breakout cables to attain the 40GbE. From all those, two most used solutions are 4 x 10 GE Breakout cable and 40G QSFP+ module for 40GbE. For core native and aggregation of 40 GbE, the ideal choice is the 40 G QSFP+ modules. There are so many variants of 40G QSFP+ modules and that is dictated by IEEE 802.3ba to hold various applications. qsfp+ sr (40GBASE-SR4) and qsfp+ LR (40GBASE-LR4) Optics are the generally used stipulation of 40G QSFP+ optics. These typical borders tried to gratify a numeral of diverse conclusions counting hold for single-mode and multi-mode fibre compatibility. Here, we are going to talk about the comparison or difference between the QSFP+ SR4 and LR4 Optics based on applications and structures.


Type of fibre and connector 

  1. Transceivers 40GBASE-SR4 QSFP+ commonly permit high bandwidth 40G optical associates more 12-fibre equivalent fibre finished with MPO/MTP connectors of multi-fibre.
  2. Transceivers 40GBASE-LR4 QSFP+ chains associated lengths of more than ten kilometres more a regular pair of G.652 single-mode fibre with connectors of duplex LC.



  1. Transceivers 40GBASE-SR4 QSFP are used by the data centres in order to connect the two switches of Ethernet with lane ribbons (12 lane ribbons can be used) OM4 or OM3 cables.
  2. Transceivers 40GBASE-LR4 QSFP+ are commonly used in deploying between ixp sites or Data centre with a solo means of fibre.


Distance of Transmission

  1. Parallel optics (40GBASE-SR4 QSFP+)

– 150 m on OM4 –10G on 4 fibres/ direction

– 100 m on OM3–10G on 4 fibres/ direction


– 10 km on single-mode– 4λ x 10G 1300 nm region


Wavelength (nm)

  1. 40GBASE-SR4 QSFP+: 4 x 850 nm


  1. 40GBASE-LR4 QSFP+ (de Multiplexing and multiplexing of the 4 wavelengths are directed within the mechanism): 1271 nm, 1291 nm, 1311 nm, 1331 nm


It is clarified with the above explanations that the 40G QSFP SR4 is for the short term distance along with the OM3/OM4 40G whereas QSFP LR4 is designed for a long term transmission that is used for a single-mode fibre whereas and here the digit 4 dictates the four lanes. Furthermore, they come with different connectors and different wavelengths. They used different technology and different network also.