7.0 Recommendations
It is recommended that this part, the "453" connector and M29504 termini, should continue to be listed in the GSFC PPL for use in applications where the thermal excursions are generally mild with respect to the temperature rating of the optical cable. This connector system should be adequate for vibration environment below 37 Grms, provided the alignment sleeves meet a minimum retention force with the termini ferrules. This force should be quantified. It is important to understand how the connector will be mounted and any additional force that will be extended to the connector during vibration as a result of the mounting configuration.
It is extremely important to understand sources of contamination that may interfere with the light path and physical mate of the termini. Contamination that is sufficiently large or sufficiently prevalent can cause temporary signal loss. Therefore, adequate cleaning techniques must be used to remove the contaminating material from the connector. This is difficult given the configuration of the socket contacts in particular. Further, the materials on the rear of the connector (resilient grommet and epoxy) seem to retain particulate contamination, such as metal shavings, which makes it difficult to keep the connector clean.
The goal with PC polish is to provide a fiber end that is convex and as free as possible of surface discontinuities. The termini pairs tested here had a range of polish qualities from good to poor, though none showed a degradation in optical performance that could be directly associated with the fiber end face surface. Some of the photographs suggest that large cladding edge chips can grow in size with multiple matings and thereby free glass particles that can pit or scratch the glass surface. A reliability analysis should be performed to better quantify the relationship between the types and characteristics of the surface features observed here and the long term connector optical performance. A life test utilizing thermal and tensile stress on the cable could be used in an attempt to determine time to failure for termini with significant defects.
The connector insert and grommet was significantly degraded during
this evaluation. This degradation may be due to a combination
of terminus insert/removal cycling, the build up of epoxy and
shrink tubing on the terminus (preventing proper operation of
the removal tool) or an ineffective insert/removal tool. Although
the degradation of the grommet and insert did not seem to affect
the optical performance of the connector, it did contribute greatly
to the contamination situation. All efforts should be made to
greatly reduce the insert/removal cycles when using optical termini
in this connector and to be aware of the limitations this problem
extends to the termination process (choice of materials and other
limitations on the amount of material used at the termini rear
barrel).
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