The NEC requires that cable trays must be supported by members at an interval specified by the cable tray manufacturer, but not more than 5 feet for horizontal runs to support the weight of the cables and other loads. The NEC has a requirement for ladder-type cable trays. The National Electrical Code is a set of principles designed to promote public safety and welfare, as well as safeguard public health by regulating the design and operation of electrical facilities and. The Professional Association Of Fiber Optics www. org The Fiber Optic Association, Inc. (FOA) was founded in 1995 to help develop the workforce to build the fiber optic networks to support a rapid expansion in communications and the Internet. The charter of the FOA was to promote professionalism. Indoor cables can be installed in raceways, cable trays above ceilings or under floors, placed in hangers, pulled into conduit or innerduct or blown though special ducts with compressed gas. 25” conduit shall be. Answer: No. NEC section 300-8 does not permit any tube, pipe, or equal for water, air gas, drainage, steam, or any service other than electrical in raceways or cable trays containing. While there are several specific types of listings for power cables, specifically for tray applications, there is no equivalent tray rating for optical fiber cables.