The hollow core fibers are available with FC/PC connectors and as well as spliced to standard optical fibers. When FC/PC connectorizing the hollow core fiber, a thin window (<100 µm thick) is spliced to the end facet. Thus, light is passing through two silica-air interfaces at each connectorized end. Please consider what impact this may have on dispersion, Fresnel reflection and damage threshold on your application. The similar consideration should be applied when splicing to standard single mode fibers.