Optical Connector Contamination and Its Influence on Optical Signal Performance

The thrust of the NEMI project on Fiber Optic Signal Performance was to develop fiber optics inspection criteria, which may support differing requirements based on application. The tests’ resulting data would provide OEM incoming quality and cable suppliers with specific cleanliness requirements with supporting data. Potentially, the inspection criteria could be used as an enhancement to existing TIA, Telcordia and other standards bodies. The influence of the contamination/scratches on connector optical performance, that is, Insertion Loss (IL) and Return Loss (RL), as well as on the system level performance using the Bit Error Rate Test (BERT) were investigated. It was shown that the effect of contamination / scratches on optical signal performance is dependant on the contamination type (fingerprints, carbon, metallic particles, etc.), the size of the contamination / scratches and their location on the connector end face. The influence of the contamination / scratches becomes more evident if they are located in the core / cladding areas. It was shown that particle contamination may cause a significant increase in IL (up to ten times), decrease in RL (up to 3 times) and increase in BERT results (210 times). The significant degradation in BER performance occurred when the core of the fiber was blocked: the BER signal increased by more than 100 times compared with a clean fiber at average power -12 dBm. Scratches applied to the fiber MFD (Mode Field Diameter) resulted in an increase of up to 25% of RL while scratches located in the cladding layer showed little effect on IL, RL and the BERT results. Multiple heavy scratches passing through the core caused severe performance degradation (IL, RL) and catastrophic BERT failures. Further investigations, such as mathematical modeling, are required to understand the influence of contamination and scratches on optical signal performance. The other objective of the project was to determine methods for improving the cleaning process and preventing recontamination of fiber optic connectors. This would result in the minimization of inspection and cleaning processes, elimination of false failures during test due to contaminated connectors, reduced cycle times and associated cost reductions.