Atlanta fiber system experiment: Optical crosstalk evaluation for two End-to-End lightguide system installations

A visual photometric method of measuring lightguide cross-coupling is described. Cross-coupling losses up to 100 dB can be measured with a resolution of ±1 dB. The end-to-end cross-coupling losses were measured for the Bell System's 1976 Atlanta Fiber System Experiment and 1977 Chicago Lightwave Communications Project installations. In the Atlanta experiment, the crosstalk was also measured for the unconnectorized lightguide cable and fanout ribbons, separately. Worst-case cross-coupling losses were measured to be 55 dB for far-end output-to-output and 70 dB for near-end. Results presented here confirm that properly designed parallel lightguides have negligibly small levels of optical crosstalk. However, it is shown that future optical interconnection devices that involve high-fiber packing densities will have to take crosstalk considerations into account.