Meeting the Fiber Optic Challenge with Vibratory Cable Plows

To date, much of the installed direct buried fiber optic cable has been placed by large crawler-mounted plows. However, in many areas, such as along highway rights-of-way and other routes with numerous road crossings, smaller-sized rubber-tired machines would be advantageous. Four-wheel drive vibratory cable plows have been utilized extensively by the telecommunications industry when installing copper cable, but there has been a general concern about vibration potentially damaging fiber optic cable. In order to overcome these fears, a test program was conducted in cooperation with a major cable manufacturer. Tests showed that tension required to feed fiber optic cable through a vibrated fixed-feed tube blade was much less than for isolated and static feed tubes. Operations stretching the limits of good installation practices, such as cable bend ratios as small as 4.5:1 and vibrating in place for 30 seconds, did not damage loose tube fiber optic cable under low tension. For better industry acceptance, special plow blade feed tubes and cable guides were designed, patterned after published recommendations. These were evaluated in a field trial and have since seen application in numerous successful installations of fiber optic cable.