Question 15/XV - Characteristics of line systems on optical fibre cables (Continuation of Question 24/XV 1985-88) Considering (1) that a number of Recommendations in the G.900-Series give characteristics for digital line systems on optical fibres; (2) that the operational experience relating to optical fibre systems is now rapidly increasing; (3) that advances in the technology of optical fibres and components may make feasible new generations of line systems on optical fibres, (e.g. analogue systems, high bit rate systems, wavelength division multiplexing systems, coherent systems); (4) that optical fibres may be used for in-station cabling, 1. How should Recommendations G.955 and G.956 be amended and completed? 2. How should tables in Recommendation G.955 and in Recommendation G.956 giving optical path allowances be completed? 3. How should other existing Recommendations in the G.900-Series be amended and completed insofar as they relate to digital line systems on optical fibres? 4. What new Recommendations should be established regarding new generation line systems on optical fibres? 5. What should be recommended for optical fibre in-station cabling? Points for study 1. High bit rate systems. 2. Dispersion limited systems. 3. Single-mode fibre systems employing LEDs, MLM lasers and SLM lasers. 4. 1550 nm wavelength systems. 5. Systems not optimized for maximum section length. 6. Wavelength division multiplexing. 7. Systems employing coherent detection. 8.Possible power feeding arrangements and related precautions against induced voltages and currents. 9.Environmental conditions, if some other studies appear necessary. 10. Overall design features. 11.Implications of IEC studies of optical fibre/laser safety considerations. 12.Application of Operations, Administration and Maintenance interfaces as given in Recommendation G.771 - any unique features required. 13.Design methodology - worst case versus statistical design approach. 14. Definitions and test methods of system/equipment parameters. 15.Error performance of operational systems - see annex to this Question. 16.Requirements for systems/equipment characteristics which provide transverse compatibility in order to enable equipments designed by different manufacturers to interwork and/or be utilized together in a given digital line system (i.e. the possibility of mixing various manufacturers' equipment within a single digital line system) including optical pulse shape and optical source parameters. 17.Definitions and test methods. 18.The requirements for systems operating on fibres conforming to Recommendations G.651, G.652, G.653 and G.654. 19.The use of optical fibres for in-station cabling. 20.Enhancements to the maintenance strategy requirements of section 8 of Recommendations G.955 and G.956. 20.1Monitors and alarms. 20.2 Supervision and fault location. 20.3 Protection switching. 20.4 Engineering and wiring. 21. Line systems employing optical amplifiers. Notes 1. Operations, Administration and Maintenance interfaces on transmission equipment are studied under Question 9/XV. 2. Protection switching systems are studied under Questions 5/XV and 6/XV. 3. The study of this Question should be coordinated with the study of Questions 11/XV, 12/XV, 18/XV, 16/XV, 25/XV and 29/XV. 4.Study Group XVIII is responsible for general network issues. 5. Study Group V is responsible for the study of protection against dangers and disturbances of electromagnetic origin. 6. The study of digital sections, if any, should be carried out under this Question and coordinated with the study on systems of CCIR Study Groups 4 and 9. ANNEX (to Question 15/XV) Optical line system error performance In response to a request from Study Group XVIII for the involvement of Study Group XV in error performance studies, it was recognized that information on the distribution of errors in digital line systems was required. This information was considered desirable to provide data on error occurrence, burst error length and possible loss-of-alignment and also to enable comparison of any background error ratio with error threshold requirements. The following questionnaire was prepared to obtain relevant data. Questionnaire on optical line system error performance - system bit rate - physical support (optical fibre cables) - section length and number of repeaters If possible, carry out the measurements on systems with a length near to that of the digital sections (50 or 280 km) - link characteristics (operational system, field trial, laboratory experiment) - system characteristics (e.g. source type, receiver type) - information concerning: - binary BER - pseudo-random sequence (refer to 0.151) - line code BER - multiplication factor (theoretical and measured) - does the equipment allow: - to record the sending of AIS - to record equipment faults indication - quality classification (class 1 or other) - if necessary, translation rule used, in term of length, between the measured section and HRDS objective for the considered quality classification - measurement time - measurement method (test configuration details) - percentage of: (at 10-6 (for information) ( degraded minutes: (at 10-7 ( (at 10-8 Errored Seconds (ES) Severely Errored Seconds (SES) - time of occurrence of errored seconds (in seconds) - number of errors in each errored second Note 1 - Data should be measured at the system bit rate. Note 2 - For the degraded minutes, it is suggested to use a translation parameter, from the system bit rate to 64 kbit/s channel, equal to one. For ES and SES the translation rule should be indicated. * * * Information received during the 1985-1988 study period indicated that a BER design objective of 1.10-10 is required to meet Recommendation G.821 requirements and that this objective could be readily met. Replies to the questionnaire, available during the 1985-1988 study period, generally refer to relatively short periods of time (a few hours or days) compared to the averaging periods in Recommendation G.821. Further study based on the questionnaire is required in the 1989-1992 study period to provide a statistically significant data base.