Design and Performance of Low-Loss Submarine Optical Fiber Cable for Long-Distance Submarine Repeaterless Transmission System Employing Remotely Pumped EDF and Distributed Raman Amplification

This paper describes a low-loss submarine optical fiber cable for a long-distance submarine repeaterless transmission system that employs remote pumping. The features of this system are that it has an increased signal power budget and is cost effective and easy to maintain. First, we investigated the relationship between the signal and pump losses and the Raman gain efficiency of optical fiber needed to achieve a submarine repeaterless transmission system operating at 2.5 Gbps and over a distance exceeding 370 km. We manufactured a submarine optical fiber cable based on the results and confirmed that it had low-loss characteristics. Second, we evaluated the long-term loss stability of the optical fiber with a high-power continuous wave (CW) laser light as the pump source. We confirmed that the loss remained unchanged after 1900 hours of exposure to 8W CW laser light at a wavelength of 1.48μm. This submarine optical fiber cable is being employed in a commercial submarine repeaterless transmission system between Okinawa and Miyakojima.