400G Breakout Applications

With the race to bandwidth upgrade, plenty of new configurations are coming. Today, 100G equipment is massively deployed and used and there are some ways to use this “legacy” equipment in the 400G upgrade challenge.

Indeed, Breakout DACs and AOCs are now available on the market converting a 400G signal into four 100G signals. In this way, a single OSFP/QSFP-DD port can be connected to multiple QSFP28 ports. But DACs and AOCs have distance limitations and it has quickly been necessary to develop solutions for longer distances.

A crucial part of any 400G breakout application is the Single Lambda QSFP28. While a standard QSFP28 is transmitting and receiving on four 25G optical signals, a single lambda QSFP28 transmits and receives one, PAM4 coded, 100G optical signal (DR1, FR1, LR1). This allows it to be compatible with all existing 400G standards OSFP/QSFP-DD (DR4, FR4, LR4).

So far so good, but how to connect them?

Set up N°1: DR4 to 4x DR1

In this case, an OSFP/QSFP-DD DR4 (QBP13P50E0PF) or DR4+ (QBP13002E0PF) is used in front of four QSFP28 DR1 (Q2C13P50C00F).

The setup is, in this case, rather simple since it only requires a fiber split from the MPO patch cord (to four dual LC connectors). In the case of SN or MDC connector, four separate patch cords can be used.

Set up N°2: LR4 to 4x LR1

This second setup allows user to re-use existing MUX/DEMUX already installed in their network.

The Single Lambda QSFP28 LR1 (Q2CxxyyyC00F) has to come in four variants matching the four wavelengths (1271,1291,1311 and 1311nm) used by the OSFP/QSFP-DD FR4 (QBPQLyyyE00F). By using a MUX/DEMUX the 4 signals can be sent/received through a single fiber over distance up to a couple of kilometers (taking the MUX/DEMUX insertion loss into account).

Set up N°3: 4x LR1 to 4x LR1

This set up allows user not to invest directly in 400G equipment and keep both sides of the link equipped with QSFP28 100G ports. The use of a MUX/DEMUX will give the opportunity to have a single 400G signal out of four times 100G signals located at each sides of the link.