The Rack Of Doom
Where there’s transmitter conformance testing, expect similar treatment for receivers. For this pupose, the X-Lab has its so-called “Rack of Doom,” shown here. Tests using the equipment in this rack ensure that the receiver meets the receive error rate requirements defined in the IEEE Ethernet specification. For 10 Gb technologies (including 10GBASE-T), the IEEE defines a bit error ratio (BER) target of no more than one error in every 1012 bits received. That’s one error in every trillion bits. And if that’s not impressive enough, a 10 Gb receiver must perform with this same precision even when bombarded with various types of noise or when plugged into an erroneously wired connection, which isn’t uncommon in places where techs custom-cut their own cabling.
The Rack of Doom contains multiple random noise sources, some of which get used in alien crosstalk noise testing (see below). This ensures that the PHY’s internal digital signal processing (DSP) noise-cancelling systems function properly in the presence of noise that they don’t understand and therefore can’t cancel. In 10GBASE-T communications, this usually manifests as signals bleeding into the wire from adjacent cables in a cable tray.