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Earlier posts discussed one Lambda 100 Gigabits and its significance for the coming generation with 100 Gigabits pluggable fiber optics. Today's 100G has concern for the form factor QSFP28. However, I utilize the name "pluggable optics" since the coming generation has to be a Small Form Factor Pluggable of some kind.
Let's go back a little continuing the earlier post. We stated that we operated on a more straightforward 100G plug-in optical vision. To facilitate this, we use PAM4 modulation; therefore, we can proceed with just one laser rather than four. So, we can process just one wavelength (also known as “lambda”) to transmit the entire 100Gbps data stream.
Why do we need to reduce the number of components within the module? Observe the picture above, which depicts what is inside the current 100 Gigabits QSFP28 plug-in fiber optic modules. Observe that there are essentially 4-channels appliances with a right and left optical interface. Every channel carries 25 Gigabits of non-return-to-zero (NRZ) data for 100G.
Analyze this with another picture using a typical 10 Gigabits SFP+ optical transceiver. It’s elementary. We have just one line carrying 100G data. Typically, we use one laser, photodiodes, and an easy driver circuit for photovoltaic and electro-optical conversion. This clarity is at the heart of why manufacturers can produce 20 million 10 Gigabits SFP+ modules yearly.
Finally, when 100 Gigabit Serializer-Desrializers (SerDes) are available on router ports and switch, the ASIC at the back of the port can perform forward error connection (FEC) and 4-level pulse amplitude modulation (PAM4), letting the other plug-ins carry out the electro-optical conversion. We can then use a smaller form factor SFP with 100G power-side lanes that have a connection with the router port or switch to increase the front-panel bandwidth density. We can likely call this Small Form Factor Pluggable 112.
But we are not that far yet. Meanwhile, a QSFP28 module works with PAM4 and FEC within the module, which converts 4x25 Gigabit power lines into a single 100 Gigabit line. That occurs with our released Quad Small Factor Pluggable 28 100 Gigabit FR module. Nevertheless, the advantage of implementing this Quad Small Form Factor Pluggable 28 module is that it will work with future routers and switches that adopt Small Form Factor Pluggable 112 modules when SFP112 is accessible. Moreover, we don't need to convert 4x25 Gigabit to 100 Gigabit as the fiber optic signal, and the electric interface is 100G single lane. This forward adaptability is very useful for network enhancement strategies because it prevents existing Quad Small Form Factor Pluggable 28 modules from being obsolete when we add modern SFP112-based equipment.
