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Evaluating the reliability of optical connectors
(a) Insertion loss
(b) Return loss
Fig.7 Results of the Temperature Cycling Test
(SC connectors; light source wavelength, 1310 nm)
6-3 Pistoning measurement results
Measurement results for the ferrule tip surfaces did not indicate major changes in
eccentricity and curvature radius, but the measurements confirmed that changes
occurred in pistoning compared to the initial values.
Fig.8 shows pistoning measurements after 1000 and 2000 hours of the High
Temperature Storage Test (Damp Heat), and after 500 cycles of the Temperature Cycling
Test. This report represents the direction of pistoning as a negative value. In the IEC, the
standard for tolerance is recommended as -50 to 100 nm, and this level is exceeded, but
the insertion loss and return loss measurements did not exhibit conspicuous fluctuation.
On the other hand, optical connectors with powerful insertion light may be subject to
influence by pistoning. Because of this, we face the challenge of investigating the
relationship between pistoning and optical characteristics in such areas as manufacturing
conditions.
In this research, more pistoning occurred in the Temperature Cycling Test than in the
High Temperature Storage Test (Damp Heat), regardless of whether the type of fiber
coating included Hytrel ® core or the PVC sheath. The cause for the increased pistoning is
thought to include stress in the direction of the pistoning from contraction and peeling of
the adhesive. This, in turn, is thought to be possibly caused by the effects of humidity and
the re-hardening of the adhesive at the test temperature (85°C) for reliability testing.
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Espec Technology Report No20