10 Gbit/S Ethernet test challenges twisted pair cabling Environment (1)

New installation and testing guidelines help reduce external crosstalk AXTalk)

10 gbbase-t, a 10 Gbit/s Ethernet standard based on Copper Twisted Pair wires, is currently in the development stage.

Many of the standards have been clarified in recent months, and the 10 Gbit/S Ethernet standard is expected to be finalized and released by 2006. This white paper briefly introduces the cabling requirements of twisted pair wires and the measurement and verification methods after the cabling system is installed.

10GBASE-T field test and verification Overview

The transmission capability of the cabling link cannot be defined in isolation. First, the transmitter needs to encode the digital information and generate electronic signals that can be transmitted, and then send these signals through the wiring link. Secondly, the physical link must be able to transmit the transmitter signal to the receiver across the required distance, and ensure the signal quality at the receiver input end. Finally, the receiver must also meet a set of performance parameters to ensure that the signal arriving through the link meets the technical requirements, so as to ensure the success of its own functions. Therefore, it is necessary to carefully understand the requirements of the sender, the signal encoding method, the capabilities of the receiver, and the transmission characteristics of the link, and take them as a whole.

The Institute of Electrical and Electronics Engineers (IEEE) has developed and maintained the IEEE 802.3 Ethernet standard. The 10 GB/S Ethernet Working Group will establish the 802.3an standard. IEEE uses its expertise to design and determine the active electronic subsystem, and works with the telecommunications industry association TIA) and the International Organization for Standardization (ISO) and other major cable standards organizations have jointly established performance specifications for cabling channels.

FlukeNetworks has been active in activities of TIA and ISO research committees since its establishment. Driven by Fluke Networks, a set of effective external crosstalk AXTalk measurement methods have been developed. External crosstalk is a key performance parameter for sending 10 GB/S Ethernet 10GbE signaling over a twisted pair cabling link. We will explain the meaning of these parameters and test methods.

All test parameters specified in Cat 6 TIA/EIA-568-B file * are required when the 10GBASET twisted pair is verified on site. These parameters include insertion loss, ripple loss, line-to-line to-end crosstalk, integrated near-end crosstalk, line-to-line to-end crosstalk, integrated remote crosstalk, propagation delay, length, and latency time difference.

The limits for testing 10GBASE-T are the same as those for testing Cat 6 with a maximum frequency of 250 MHz, but to support 10 GB/S Ethernet technology for higher data transmission rates, the frequency range and performance requirements of these tests are extended to 500 MHz. in addition, on-site verification of 10 GB/S Ethernet must involve the external crosstalk test parameters discussed in this White Paper.

Measure the test taker's knowledge about external crosstalk and its impact on the performance of 10 Gb/s.

10GBASE-T signaling requires a wiring bandwidth of up to 500 MHz, which is significantly higher than the 100 MHz bandwidth of 1000BASE-T1 Gigabit/second Ethernet. These frequencies are very high, so an important set of Interference measurement parameters must be added to the wiring test parameters. This new set of test parameters is called external crosstalk.

Crosstalk measures signal coupling from one line to another in a twisted pair cabling link. This coupling will produce noise interference to the center online, so we don't need it. The effect of crosstalk is very similar to that of a transmission line affected by noise. The receiver cannot distinguish the signal sent from the transmitter at the other end of the link from the noise produced by crosstalk. Crosstalk is a key performance parameter in data communication activities. The degree of crosstalk deepens with the increase of the signal sending frequency, and the higher the signal frequency, the more severe the signal attenuation will become weaker when it is transmitted along the link ). It is precisely because of these two effects that we need to find such a frequency: the noise produced by crosstalk is equal to the signal sent by the transmitter. For the 100 mCat 5e channel, the frequency is usually around 120 MHz, and for the entire Cat 6 channel, it is usually around 240 MHz.

If an electronic device does not have advanced digital signal processing technology, it will not be able to achieve reliable signal transmission at this frequency or even higher. This phenomenon sets a limit for the bandwidth of twisted pair wires.

Nearby crosstalk or "NEXT") measures the crosstalk signal at the end of the wiring link that sends a test signal or interference signal. Describes the near-end crosstalk in a system with two-wire pairs. IF signal transmission is performed on multiple pairs at the same time, as in 1000 BASET and 10 GBASET, you must also consider and test the remote crosstalk FEXT.) See figure 2 ).

And the crosstalk in the description occurs between the wire pairs of the same cable in the same outer cable ). The external crosstalk is exactly the same as this phenomenon, except that the crosstalk coupling occurs between line pairs in different but adjacent two cabling links.

External crosstalk is an urgent problem to be solved because it is the main interference or noise source for 10 GbE applications using UTP cabling. Figure 3 shows the external crosstalk produced by a line pair in the adjacent cable.

The measurement of external crosstalk will include the external near-end crosstalk between line pairs and the external remote crosstalk. Because the overall impact of numerous wires in the harness on the tested wires is required to be evaluated), the cables in the harness should be calculated and integrated with the external near-end crosstalk PSANEXT) and integrated external remote crosstalk PSAFEXT ).