NEXT and FEXT models for twisted-pair North American loop plant

Measurements of near-end crosstalk (NEXT) and far-end crosstalk (FEXT) in 26-AWG and 24-AWG polyethylene insulated cable (PIC) twisted pair cables are presented. This data is used to develop crosstalk models that indicate existing T1.417 Standard NEXT and FEXT models are probably conservative by about 5 dB for 25-pair binder groups. However, many cables start from wire centers as pulp cables of 100-pair binder groups. Even if most of these older pulp cables are 26-AWG, prudence dictates that a more conservative model be used for these cases. On a going forward basis for new and rehab construction, it should be recognized that PIC (air core and filled) cables with not larger than 25-pair binder groups are the predominant cable media supplied by manufacturers for feeder and distribution loops. Results for NEXT in 12-pair binders are also analyzed and show that 26-AWG cable has about 2 dB more NEXT loss than 24-AWG cable and 12-pair binders have about 2 dB more NEXT loss than 25-pair binders. In addition, the NEXT loss separation between adjacent binders of 12 and 13 pairs is found to be not more than 10 dB as compared with the more optimistic 15.5 dB assumed within the industry.