Question 18/XV - Availability and reliability of line systems on optical
fibres (Continuation of Question 28/XV 1985-88)

Considering

(1) that the reliability of digital systems on optical fibre is of
importance in achieving an adequate service availability on the
transmission paths or channels routed on those systems;

(2) that a wide range of factors impact on the reliability that can be
achieved;

(3) that proposals have been made concerning reliability and
availability issues, including their definition;

(4) that the greater the use of fibre systems bandwidth the higher the
cost of system outage;

(5) that the cost due to a poor quality (reliability/availability) may
amount to a significant percentage of the material costs,

1. What should be recommended for reliability and availability
objectives for line systems on optical fibres?

2. What should be recommended for reliability and availability
objectives for the hardware and software elements making up line systems
on optical fibres?
3. What definitions should be recommended to ensure that field-related
experience about failure modes, and their effects, could be timely used
to improve the quality of fibre optic systems?

Points for study

1.The definitions related to availability and reliability issues as
applied to line systems on optical fibres.

2.Cost optimized procedures for the allocation of availability
objectives for the various parts of a system.

3.The need to set availability and reliability objectives for the
various elements that may make up a line system on optical fibres, e.g.:

- cable
- regenerators
- multiplexing equipment
- terminating equipment
- power supplies
- protection switching equipment.

4.Systems architecture, cable routing and redundancy.

5.Maintenance procedures.

6.Environmental conditions.

7.Uncontrollable natural phenomena, e.g.:

- lightning
- flooding
- ice loading.

8.Procedures and examples showing the calculations necessary to
determine the appropriate allocations of availability and reliability
objectives to the system elements, (examples of these elements are given
in point 3 above). Calculation of examples covering long-distance,
inter- exchange and local network applications would be useful.

9.Measuring procedures for assessing reliability/availability objectives
as applied to line systems on optical fibres.

Notes

1. Study Group II is responsible for coordinating the study of
reliability and availability.

2. The study of this Question should be coordinated with the study of
Questions 5/XV, 6/XV, 11/XV, 12/XV, 13/XV, 14/XV, 15/XV, 16/XV, 17/XV,
19/XV, 25/XV and 29/XV.