A chain of LEDs is formed from link units connected by wire pairs in electrical circuit. At least one wire pair is connected to a link unit to form external power supply wires. Each link unit is made of a tray housing a PCB in the housing, and LEDs mounted on the PCB in electrical connection with the wire pairs. Cured waterproof resin inside the tray housing encases the printed circuit board, the wire pair connection point to the PCB and the lower half of the light emitting diode elements.