Doing weak power engineering, fiber optic patch cords can not be connected without fiber optic loopback adapters, different modes of fiber optic loopback adapters with different color identification, gray for multi-mode fiber optic loopback adapters, blue for single-mode, lake blue 10 Gigabit OM3, green APC, rosy red OM4, aqua green OM5.VANDESAIL - Accelerating the world with technology.