Statistical Behavior of Crosstalk Power Sum With Dominant Components

Crosstalk interference is a prime limitation on the transmission capacity and the performance of digital transmission systems, such as Tl, 1 TIC,2,3 SLC-40,4 T1D,5 and SLC-96,6 on twisted multipair cables. An important step in the design of digital systems and their associated engineering rules is the characterization of the power sum of pair-topair crosstalk loss. The crosstalk power sum is the total crosstalk interference which appears on a given pair as a result of coupling from all disturbers on other pairs. The crosstalk power sum of a T-carrier system can be decomposed into two components: one component originates from crosstalk among 1363 wire pairs in the cable, and the other component originates from crosstalk among wire pairs on the backplane of the repeater apparatus case and the associated connectors and stub cable. At each repeater location of a T1 system, an apparatus case is used to house 50 regenerators of 50 one-way T1 systems. Figure 1 shows the 25-slot arrangement of the 466-type (without lightning protection device) apparatus case. Each slot holds two Tl regenerators. Figure 2 shows a portion of the wiring arrangement between the stub cable and the repeater connectors on the backplane of a 466-type apparatus case. The crosstalk originating from the wire pairs on the apparatus case backplane, connectors, and stub cable is known as apparatus-casecrosstalk (ACXT). In new, 800-series, plastic apparatus cases, a carefully controlled wiring layout is used to minimize the ACXT to such an extent that ACXT can be neglected in the Tl system engineering rules.