Sealing assemblies with “soft sealant” technology form a tight seal around optical cables without crushing the fibers. The assemblies seal virtually any size fiber down to a 400-m m outer jacket without epoxies or other outgassing materials. Several fiber-optic assemblies can be used with multihole glands to provide a number of sealed penetrators through a single port. The assemblies' helium leak rating is 1 3 10 6 scc/sec and transmission losses are less than 0.3 db typical (not including connectors). Pressure ratings up to 1,000 psi are standard, with a 3,000-psi option available.