Heavy Duty Loose Tube OFNR Cables are ideally suited for harsh environment applications including mining, steel mills, refineries, lumber mills and many other situations requiring a rugged cable construction. These cables have been specifically designed to have greater tensile, crush and impact ratings. With a dual layer of flexible strength members and a double layer of rugged flame retardant and sunlight resistant jackets, this cable design possesses features ideal for environmentally demanding applications. The heavy duty loose tube design features optical fibers placed inside PFM gel-filled buffer tubes. The core is constructed by stranding the buffer tubes around a central member using reverse oscillating lay (ROL). The core is wrapped with flexible strength members and covered by a water-blocking tape, then encased in a black flame resistant jacket. A second layer of flexible strength members is applied and then encased in a black, flame and sunlight resistant jacket. Rip cords are included under each jacket for ease of entry.