Abstract: An improved flexible multi-duct conduit system for housing and protecting subterranean fiber-optic cable comprises matable sections each having an outer casing and a plurality of inner ducts for carrying the cable. An rubberized inner duct coupler is provided at one end of each section for aligning and sealing the inner ducts of adjacent sections when the sections are joined together end-to-end. An outer casing coupler for coupling and sealing the outer casings of adjacent joined sections comprises a cylindrical collar that extends around the ends of two adjacent sections. Sealing gaskets disposed between the outer casing ends and the collar insure against ingress of moisture and other corrosive subterranean elements into the outer casings. The inner ducts are bendable and the outer casings are formed with corrugated exterior surfaces so that the entire system, when assembled in the field, can be bent about an arc to accommodate turns and the like.