Ultra-precise multi-fiber optical connectors for astronomy

The increasing sensitivity and precision of modern astronomical instruments demand optical fiber connections with high stability in cross-mating and exceptionally low insertion loss reaching 1% (0.05 dB). Conventional multi-fiber connectors, though suitable for telecommunications, introduce excess attenuation, Fresnel reflections, and alignment instabilities that degrade throughput and calibration accuracy in astronomy. This work presents the design of ultra-precise optical multi-fiber connectors developed for astronomical use. Fabricated using femtosecond-laser 3D printing, they achieve sub-micron ferrule tolerances. Preliminary metrology shows excellent hole alignment and roundness indicating strong potential for achieving high fiber-to-fiber coupling efficiency. Initial throughput tests for three simultaneously connected fibers show losses as low as 0.95% (0.04 dB). Further throughput and FRD characterization will assess stability and repeatability of such connectors.