EMC Performance and Alien Crosstalk Conformance for Cat8 Cables

摘要

With the recently released IEC 61156-9/-10 and TIA 568-C.2-1 standards, EMC and Alien Crosstalk testing became de facto a requirement for Cat8 cables. Even if still historical differences exist between these two standard families, both specifications came closer to each other given that the same Ethernet protocol, IEEE 802.3bq, better known as 25G/40GBase-T, must be supported by these cable types. Alien crosstalk was first introduced back in 2008 when crosstalk between adjacent cables had to be quantified for the development of Cat6A. Though, it was used for unshielded cables only. Regarding EMC (Electromagnetic Compatibility) testing for shielded cables, Coupling Attenuation (AC) is being used to differentiate different types of cables and screening efficiency levels. However, since Cat8 is aimed at shielded cables, both standardisation bodies had to revise and (re)adjust their own specifications. The required parameters are the same, although on IEC side, an exclusion rule was introduced to avoid the timely consuming Alien Crosstalk testing. Nevertheless, regarding Transfer Impedance (TI), both committees have set requirements in their respective standards. In this paper, we'll review the challenges of testing against EMC and Alien Crosstalk. We'll report measurement data and highlight the pitfalls in performing these types of tests.