London, UK The Fibreoptic Industry Association has started to develop a Technical Support Document to address the increasing problem of over-specification of splice losses. To be launched at a seminar in May 2004, the TSD will establish, in a commercially neutral manner, the most appropriate way in which to specify and verify the performance of optical fibre fusion splices; it will also define reasonable and commercially acceptable limits for the splices under specific conditions.
Fusion splicing is a well-proven approach for the provision of low loss, low return loss and environmentally stable connections both internal and external to buildings. Over the years, the capability of fusion splicing equipment has improved substantially, as has the control over the tolerances of optical fibres themselves, resulting in a steady reduction in achievable splice loss to the point where further significant performance improvements can no longer be made without direct influence over the optical fibres.
The FIA believe that unrealistic demands for splice loss performance, flawed in terms of what is specified and/or how it is specified, are often included in specifications. The impact of specifying overly ambitious or incorrectly defined splice loss requirements should, says the FIA, concern both the client and the installer. The installer may be faced with a considerable degree of rework that can have dramatic commercial consequences, while the client may be faced with considerable project delays, the resolution of which will add further costs.
Over-specification can arise from a number of causes. Clients may be influenced by the claims of fusion splicing equipment manufacturers, who rightly provide favourable, best case specifications for their machines; no account may be taken of the tolerances of the optical fibres that are seen in the field or clients fail to recognise the range of, and differences between, optical fibres that may be encountered and their influence on the performance of splices made between them.
IEC 60793-2-50 specifies five different single mode optical fibres between which fusion splicing will result in modified performance when compared with splicing between singlemode optical fibres of the same type.