Underwater stainless steel tube armored optical fiber unit (GTXTG3U) is a seamless steel tube formed by putting 250μm colored optical fiber into loose-tube stainless steel tube, longitudinally welding the steel tube strip after molding, and filling a special fiber paste buffer layer in the middle, which can protect the optical fiber vertically, and at the same time, it is equipped with stainless steel wire armor and TPU wear-resistant sheath, which has good water resistance, corrosion resistance and wear resistance, meets the sealing performance in underwater environment and effectively prevents water infiltration and erosion. It is mainly used in ocean engineering, underwater detection, military underwater control and measurement system, etc.