Field Trial of Optical Fibre Cable-TV System Optical Fibre System for ...

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209 If the customer does not have special requirements as regards the presentation of reliability data, Ericsson usually provides a separate report with data concerning: - failure rate and MTBF for individual function blocks (e.g. magazine or shelf) - failure rate, MTBF, trustworthiness reliability, availability and down time for a selected, worst case system or link combination - failure rate and MTBF for the whole equipment quoted for - maximum number of failures for equipment in accordance with the two previous items, which with a certain probability will not be exceeded during a given period of time - the prediction method and its trustworthiness These data are a best estimate, and in the case of a guarantee a higher confidence level is chosen. The amount of equipment, operating conditions and verification methods must also be carefully specified. There are different methods and models for verifying that the equipment meets the guaranteed reliability. In all cases, however, the test plan must define: - the equipment to be tested - the beginning and end of the test period - operating conditions and failure concepts - statistical evaluation method. The text in the technical part of the guarantee should be clear, unambiguous and easy to understand, and only contain data that can easily be checked. It could be formulated as follows: "An MTBF>6.7 years is guaranteed for the specified equipment, i.e. a failure rate z
210 Fig. 7 The system down time as a function of the down time for the multiplexing equipment. System = multiplexer + line system a^H^i Coaxial system for 140 Mbit s including mechanical damage to the cable mmmm Optical fibre system. 140 Mbil s •• •• Down time for the system (minutes/year) 1000 - 100 Coaxial system, 140 Mblt/s Coaxial system. 12 MHz Optical fibre system for 140 Mbitys with line system redundancy permits up to C = 30 failures. The guarantee is considered not to have been met if more than 30 failures occur during the period." In this calculation it has been assumed that both the producer's and the consumer's risk is 10%. For the manufacturer this means a risk (10%) that the equipment is rejected (C>30 failures) in spite of the fact that its real MTBF meets the requirements (i.e. MTBF>6.7 years). At the same time the customer runs a risk (10%) of accepting the equipment (C
Page 1 and 2:
ERICSSON REVIEW 4 1985 Field Trial
Page 3 and 4:
Trial of Optical Fibre Cable-TV Sys
Page 5 and 6:
Head end (HC] 280 Mbit/s Farsta aut
Page 7 and 8: 158 Switching equipment Fig. 7 Futu
Page 9 and 10: 160 Fig. 10 The teleconference room
Page 11 and 12: GERHARD GOBL Public Telecommunicati
Page 13 and 14: Fig. 5, above left Two-channel A/D
Page 15 and 16: Digital input signals Digital outpu
Page 17 and 18: Power ZAV 280/4 has individual powe
Page 19 and 20: Wavelength Division Multiplexing fo
Page 21 and 22: 172 Subscriber side BP-890 Controll
Page 23 and 24: Fig. 8 Transmission characteristics
Page 25 and 26: Most computer cabinets are 19" wide
Page 27 and 28: 178 Fig. 5 Modems in Series 7 Modem
Page 29 and 30: Computer Aided Production of Plasti
Page 31 and 32: Fig. 4 Product geometry displayed o
Page 33 and 34: Rectifier for Mobile Telephone Syst
Page 35 and 36: I OR | OFU OS I CMUP HlsHi W±±±h
Page 37 and 38: 188 Fig. 6 The rectifier with the o
Page 39 and 40: Fig. 9 Rectifier BMJ A01 001 with t
Page 41 and 42: The Renewal of the London Undergrou
Page 43 and 44: 194 Rickmansworth, and the Loughton
Page 45 and 46: 196 Fig. 5 Optical fibre cable rout
Page 47 and 48: 198 In planning the optical fibre n
Page 49 and 50: Fig. 9 The digital telephone DIAVOX
Page 51 and 52: 202 Fig. 11 Transmission equipment
Page 53 and 54: 204 Fig. 2 Automatic testing of mul
Page 55 and 56: 206 Relative occurrence for F Fig.
Page 57: Fig. 5 Field testing of a 140 Mbit/
Page 61 and 62: MTBF (years) Equipment 2-5 Transmul
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