Correlation study between contamination and signal degradation in single-mode APC connectors

This paper summarizes the correlation study between contamination and scratches on singlemode APC connectors and signal degradation; leading to an Acceptance Criteria Matrix. The study is a continuation of International Electronics Manufacturing Initiative (iNEMI) research on development of cleanliness specification for singlemode angled physical contact (SM-APC) connectors. Twenty-five APC SC connectors on one-meter patch cords were used for this study. The Design of the Experiment (DoE) was a multi-step process that involved: (1) inspecting, cleaning and inspecting connectors being tested (devices under test, or DUTs) and launch connectors; (2) making multiple matings and dematings of each DUT, in a pristine state, with a reference connector, and recording Return Loss (RL) data after each cycle; (3) manually applying dust to the cleaned end-faces of the DUTs; then (4) mating contaminated DUTs with clean reference connectors at least five times, taking RL measurements after each mating and saving fiber end-face images for both connectors. It was shown that connectors with the contamination at the core (9um diameter) demonstrated a dramatic decrease in average RL of 14.2 dB. In comparison, the samples with contamination on the cladding and clear core demonstrated a negligible change in RL of 0.15 dB. For highly contaminated samples in the cladding layer, we found the changes of RL to be about 5-6 dB. Further investigation established that particle migration during successive matings also occurs on the ferrule within the contact zone (approximately <250 μm in diameter). Polishing scratches had no impact on RL of APC connectors. Based on the experimental data described in this paper, an inspection criteria matrix is proposed for SM-APC connectors including the zone definitions and number of allowable defects (contamination and scratches) for each zone. The recommendations on pass/fail criteria have been provided to the IEC (International Electrotechnical Committee). It is expected IEC-61300-3-25, which contains these criteria, will publish in 2009.