100G Transceivers: CFP/CFP2/CFP4 and QSFP28

With bandwidth demands keep growing, network service providers are looking at 40G or 100G to accommodate the constant traffic surge. For 40G QSFP+ transceivers, they are interfaced with MTP/MPO or LC connectors, which has been introduced in a previous post: 40G Transceivers With MTP/MPO Interface vs. 40G Transceivers With LC Interface. So this article will introduce 100G transceivers (CFP/CFP2/CFP4/QSFP28) which have different interface types.

100G Transceivers Standards

The 100G optical transceiver market is fragmented by many different implementations. Besides the IEEE standards, there are also 100G transceivers defined by MSA. The following table lists part of the 100G standards.

From the table above, we can see that there are three different interface types for 100G transceivers — 24-fiber MPO, 12-fiber MPO and LC duplex. The 100G transceiver with 24-fiber MPO interface uses 20 fibers to transmit data, with 10 lanes at 10 Gbps per lane (10 transmit and 10 receive). The 100G transceivers with 12-fiber MPO interface use 8 fibers to transmit, with 4 lanes at 25 Gbps per lane (4 transmit and 4 receive). This interface standard has been introduced alongside the 100G QSFP28 transceivers to make 40G to 100G upgrade as seamless as possible. And the 100G transceivers with LC interface work over single-mode fiber cables for long-distance transmission.

100G Transceivers Types

After knowing about the 100G transceivers standards, let’s move to the 100G transceivers types. There are 100G CFP/CFP2/CFP4 and QSFP28 transceivers. CFP was designed after SFP, but is significantly larger to support 100 Gbps. The electrical connection of a CFP uses 10 x 10Gbps lanes in each direction (RX, TX). The optical connection can support both 10 x 10Gbps and 4 x 25Gbps variants. With improvement in higher performance and higher density, CFP2 and CFP4 appeared. While electrical similar, they specify a form factor of 1/2 and 1/4 respectively in size of CFP. CFP, CFP2 and CFP4 modules are not interchangeable, but would be inter-operable at the optical interface with appropriate connectors.

The 100G QSFP28 transceivers offer 4 independent transmit and receive channels, each capable of 25Gbps operation for an aggregate data rate of 100 Gbps. Among the various 100G transceivers, most of switch vendors choose the QSFP28 transceivers, because they make deploying 100G networks as easy as 10G networks, increasing density, decreasing power consumption and decreasing your price per bit. It’s also notable that the QSFP28 has the same physical size as the QSFP+ commonly used for 40G traffic. This means that switch vendors can increase the traffic throughput by a factor 2.5 without the need to redesign the front panel of their switches.


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Originally published: www.fiberopticshare.com/100g-transceivers-cfpcfp2cfp4-qsfp28.html