First, allow me to say these indeed to do exist, the RJ-45 based 10GBaseT SFP+ modules, a company called Methode Electronics manufactures both a SFP+ based module and a X2-RJ-45; however, we’ll only really talk about why a RJ-45 based 10GBaseT SFP+ transceiver still isn’t practical for lengths beyond 30m, with present technology.
The number one issue we have, with the current technology today in 2017, is the number of transceivers required for distances greater than 30m using 10GBaseT SFP+ modules. The incredible number of transistors will consume an enormous amount of energy per port, and the heat generated by the operation of such modules will be monumental, to say the least. Also, with distances greater than 30m, the amount of heat generated needs to be pulled away from the circuitry and will require large heat sinks, which will increase the bulk of the switch itself or careful consideration of airflow characteristics around the SFP+ ports, including higher speed and higher volume fans (which in turn would also consume more energy themselves) further increases the power demands of a switch utilizing SFP+ modules for 10GBaseT SFP+ modules. X2 modules are indeed out there, but X2 is a different form factor to begin with and I won’t be discussing this here.
Why do I reference 30 meters?
Why do I reference distances greater than 30 meters (30m)? Two reasons: 1. When people want to look at Cat6a/7 for long haul connectivity (to somewhat come close to the distance of multi-mode fiber optics on OM4 fiber cables) 2. Current technology at the time of this writing restricts engineering a 10GBaseT SFP+ module for distances of up to 30m using about 2.5W of energy per port. Once again, please look up the company Methode Electronics and their white paper on 10GBaseT SFP+ optics, its pretty cool stuff.
Who wants this?
Now, what audience cares about utilizing such stuff as copper for distances at 100m? In the enterprise market you’ll likely never see anyone think about using copper for spanning distances close to 100m, especially in the Data Center where the copper cross-connect is disappearing in favor of 10/25/40/50/100G fiber cross-connects, because the cost of these optics are dropping fast. When I say 40G here, I am also assuming the use of Cisco 40G BiDi transceivers because they allow you to utilize existing LC based fiber infrastructure. However, service providers are still interested in utilizing copper back haul connections for distances close to 100 meters because, if the SFP+ modules are cheap enough along with the cost of laying the Copper, they’ll want to utilize this. You’ll likely see such things as connections at last mile (rather under a mile, a lot) or between two offices or central offices, cost will always play a factor in emerging technologies, aside from, and separate from, engineering capability to manufacture at scale. So, now you know, why you’re just not seeing mass produced 10GBaseT SFP+ modules on the market. This is not to say there isn’t development being done by some of the major plays in data center networking, I’ve heard rumor Cisco Systems is actively looking to build a reliable, cost effective, 10GBaseT SFP+ module, so we should all keep an ear to the ground to learn more about this, if this is true.