Interconnect Solutions Blog

For point to point connections that run between blades, boxes and racks, cable diameter has been an issue relative to airflow, PoE bundle heat build up, routing flexibility and weight. As a response, 30awg cabling has been preferred and users have gotten use to this dominate gage. Even 32awg cabling has been used in significant volume to address these issues.

As data rates have increased, we have seen a large growth of active copper cabling usage in order to keep the 30awg preference and maintain needed cable lengths and topologies. We have also seen the fast rise of active optical cabling to deal with data rate performance versus link lengths.

Now we are developing 24-28Gb/s per lane links in various standards bodies like Infiniband. Based on feedback from DataCenter engineers and managers, the new Infiniband EDR spec will not have 24awg in the specification, the maximum passive copper gage is likely 26awg. Some members are saying it should just have 30-28awg. At this data rate and gage size range, passive copper will only reach about .5-2 meters depending on PCB trace versus cable length trade offs.

Even using active copper at this data rate range, the wire gage and length story is not so great as it was in the old days of 2.5Gb/s per lane. So active optical cabling has become a lot more important in achieving optimized cable diameter and link lengths. Many OEMs and active equipment users do not like having so many media types and are strategizing to keep the link types and lengths options simplified.

Ultimately we seem to be heading towards using the smallest media size option, single mode fiber for many and most applications at any length and data rate. This seems like a major inflection point in the history of interconnection media types; just my opinion….

PS. In the old Fibre Channel days we had to use 21-22awg copper to achieve link lengths, but there was room to spare. Back then most of Fibre Channel links were copper which was embarrassing because this technology called itself Fibre Channel. Now there is no copper media being specified in the latest 28/32Gb/s specification so finally Fibre Channel is all about fiber. Got fiber in your diet?