This Part of EN 4533 examines the termination aspects of fibre optic design for avionic installations. By
termination is meant the mechanism used to interface from one component (usually a fibre) to another. This is
normally performed by a connector, which aligns the fibre with another component (usually another connector)
to a sufficient accuracy to allow continued transmission of an optical signal throughout the operational
envelope.
This Part will explain the need for high integrity terminations, provide an insight into component selection
issues and suggests best practice when terminating fibres into connectors for high integrity applications. A
detailed review of the termination process can be found in Clause 4 of this part and is organised broadly in
line with the sequence of a typical termination procedure.
The vast number of cable constructions and connectors available make defining a single termination
instruction that is applicable to all combinations almost impossible. Because of the problems of defining a
generic termination instruction, this handbook has concentrated on defining best practice for current to near
future applications of fibre optics on aircraft.
This has limited the studies within this part to currently available 'avionic' silica fibre cables and adhesive filled
butt-coupled type connectors. Many of the principles described however would still be applicable for other
termination techniques. Other types of termination are considered further in the repair part of this handbook.
1.2 Need for high integrity terminations
In order to implement a fibre optic based system on an aircraft it is vital to ensure that the constituent
elements of the system will continue to operate, to specification, over the life of the system. An important
aspect of this requirement is the need for reliable interconnection components. This is often expressed as the
need for reliable connectors, but in reality it is the need for a reliable cable to connector termination process.
The essence of this requirement is the need to assure reliable light transmission through each optical
connector throughout the operational envelope. This needs to be achieved through a robust process that
enables a high level of optical performance over the lifetime of the terminations.
Many factors can contribute to an optical connector's in-service performance, such as basic connector design,
choice of optical fibre, cable, operating and maintenance environment etc. However, one of the main factors
governing in-service connector performance is the quality of the cable to connector termination.