There are four general types of trays mentioned in the NEC, ladders, troughs, channels, and solid bottom trays. “A cable tray is a cable tray—why are there so many types?” The answer is simple: different cable characteristics and installation environments demand different tray designs. Cable weight, heat generation, bend radius, environmental exposure, and maintenance access all directly influence which. 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. According to the 2014 National Electric Code® (NEC), any listed optical fiber cable is acceptable for a tray application. Ladder Type Cable Tray The ladder type cable tray consists of two side rails connected by rungs, allowing excellent airflow around cables.