40GbE Transmission With Parallel Optics

As data center virtualizes more of their servers and storage, the need for speedy network connections increase, which means that 10GbE transmission can’t satisfy users’ need any more and it is time to migrate to 40GbE transmission. Many famous vendors has provided various 40G products and technologies to cope with the development of 40GbE network, like parallel optics. This post will give a detailed introduction of parallel optics for 40GbE transmission in the following part.

What Is Parallel Optics?

Parallel optics, also known as parallel optical transceiver, are a term which refer to a type of optical communication technology as well as the devices on either end of the link that transmit and receive information. Different from traditional fiber optic communication, parallel optical communication deploys a different cabling structure, which is primarily targeted for short-reach multimode fiber systems that are less than 300 meters. In parallel optical communication, the devices on either end of the link contain multiple transmitters and receivers. For example, four transmitters on End A communicate with four receivers on End B, spreading a single stream of data over four optical fibers.

Benefits of Parallel Optics

As we have mentioned above, parallel optical communication uses multiple paths to transmits a signal at a greater data rate than the individual electronics can support. It can either lower the cost of a given data rate by using slower, less expensive optoelectronis or enable data rates that are unattainable with traditional optical transmission. Besides, parallel optics offer an economical solution that utilizes multimode fiber, which is optimized with VSCEL sources, meaning that for speeds faster than 16G, parallel optics is the most practical and cost-effective solution.

Common Parallel Optics for 40GbE Transmission

To enable high-bandwidth 40G optical link, 40G parallel optical transceivers typically use the left four 10G channels to transmit and the right four 10G channels to receive over 12-fiber parallel MPO or MTP fiber cable, leaving the middle four channels unused as shown below. Taking the advantages of small size and high performance, 40G parallel QSFP+ optical transceiver has become the dominant transceiver module for 40G Ethernet applications. In parallel optical communication, 40G-QSFP-SR4 and 40G-QSFP-CSR4 are the two mainly deployed modules for 40GbE transmission.


40G-QSFP-SR4: 40G-QSFP-SR4 primarily enables high-bandwidth 40G optical link over 12-fiber parallel fiber terminated with MPO/MTP multi-fiber female connectors, which can support link lengths of 100 meters and 150 meters, respectively, on laser-optimized OM3 and OM4 multimode fibers. It can also be used to connect with four 10GBase-SR optical interfaces using an 8-fiber MTP to LC breakout cable.

40G-QSFP-CSR4: 40G-QSFP-CSR4 extend the reach of the IEEE 40GBase-SR4 interface t0 300 meters and 400 meters on laser-optimized OM3 and OM4 multimode parallel fiber respectively. It can be used for native 40G optical links over 12-fiber parallel cables with MPO/MTP female connectors or in a 4x10G mode with parallel to duplex fiber breakout cables for connectivity to four 10GBase-SR interfaces.

40GbE Connectivity Solutions With Parallel Optics
Solution 1: Direction Connection By MTP Trunk Cable.


Solution 2: 10GbE to 40GbE Transmission by MTP to LC breakout Cable.



The need for bandwidth continues to rise steadily and many technologies are already waiting in the wings with 40GbE or even 100GbE. Parallel optics have proven to be an excellent solution for delivering 40G or 100G transmission especially within a data center environment. It provides a flexible, high density option for quickly connecting service and is a reliable high speed solution for many data networks. If your data center hasn’t shifted from 10Gbps to 40Gbps, now it’s your chance by deploying 40GbE with parallel optics.


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