the resulting system has to be cost competitive with standard carefully stowed within a splice housing and organiser. It is normal alternatives. Technological prediction is a dangerous game, but it References 15/17 would seem that today's standard fibre has an assured future by Table A15.1 Far end cross talk ratios for 2.6/9.5mm coaxial virtue of its outstanding performance and the massive investment pair. already committed by operators in their cable networks. Section length Frequency band FEXT ratio 0.06 to 4.3MHz 15.11 References 4.5km 0.3 to 12.5MHz Allard, R.C. (1990) Fiber Optics Handbook for Scientists & Engin- 1.5km 4 to 62MHz 130dB eers. McGraw-Hill, Section 2.1.1. Barnes, S.R. et. al. (1985) The Effect of Hydrogen on Submarine Optical Cables. Electrical Communication 59 (4). Bury, J.R. and Joiner, D.A. (1985) Versatile High Performance Where f is the frequency in MHz, and the tolerance on impedance Filling Compounds for Telecoms Cable Applications. In Pro- is +10hm. ceedings of the International Wire and Cable Symposium. Attenuation Cannell G.J. et. al. (1988) Access Methods for Non-Intrusive Opti- cal Fibre Networks. In Proceedings of the International Wire The nominal attenuation is 18.00 +0.3dB/km at 60MHz at 10°C. and Cable Symposium. Nominal at 1MHz is 2.32dB/km. CCITT (1989) Blue Book. Vol 111, ITU Geneva. Above 1MHz it is 0.01+2.3Vf +0.00ff dB/km. Dummer, G.W.A. and Blackband, W.T. (1961) Wires and R.F. Cables. Pitman. Construction Flatman, A.V. (1988) Universal Communications Cabling - A Inner diameter is 2.6mm solid wire. Building Utility. ICL Technical Journal pp. 117-136. Outer conductor is 0.25mm copper tape. Flatman, A.V. (1989) Open Systems Cabling as a Building Utility. Internal diameter is 9.5mm over insulation. Electronics and Communication Engineering Journal (IEE) 1 pp. 152-158. Impedance regularity Mazda, F.F. (1981) Electronics Engineers Reference Book 5th Edi- A cable suitable for 60MHz analogue or 560Mbit/s digital systems tion, Butterworth Scientific, Section 56.18. must exhibit 