Abstract This work outlines technical specifications of the undersea fiber optic communication channel bandwidth, capacity with taken into account the maximum and minimum extended fiber cost in the presence of amplifiers stations. The number of amplifiers in the amplification stage are addressed based on the amplifier distance to strength the light signal in water depth after 5 km distance. The fiber channel capacity is estimated at different water depth and at the surface of the water. Minimum input signal power and required detectable received power are adjusted to ensure the high data rates in submarine cable systems under the best and worst conditions of the seawater pressure. The study emphasizes the high data rates transmission can be achieved at a distance of 10 km depth.