Polarization fluctuation characteristics of optical-fiber submarine cable under 8000-m-deep sea environmental conditions, optical-fiber submarine cable coupling under periodic variable tension, and cable performance during and after installation, are presented. As a worst case, it is demonstrated that the maximum frequency spectrum of polarization fluctuation is less than 200 Hz under dynamic composite stress states. It is found that the polarization fluctuation of the optical-fiber submarine cable coupling changes linearly with periodic variable tensile forces. It is confirmed that the power spectrum of polarization fluctuations are less than 50 approximately 60 Hz, and the maximum power spectra are between 5 and 10 Hz during the cable installation within a maximum cable tension of 18 kN (1.8 tons) and the cable laying speed of 3.5 knots, respectively.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>