海底光缆是现代国际通信的主要基础设施。海底沙波运动的存在，给海床上光缆铺设时放缆余量的计算带来困难。如果放缆余量偏少则会造成铺设完的光缆在沙波两个波峰间存在悬空段，悬空段光缆在洋流和内波的作用下产生的涡激振动及与底床的往复运动会产生磨蚀，因而缩短光缆安全寿命。因此，海底光缆工程设计时，合理计算放缆余量是十分主要的工作内容。本文探讨海底沙波的成因、沙波床面上光缆受害的机理，分析了光缆放缆余量的计算方法，为海底光缆工程设计提供参考。

Submarine optical communication cables are the main infrastructure for modern international communication. Due to the presence of underwater bedforms， the difficulty to lay optical cables on the seabed is increased. If the amount of cable laid is less than required， it would cause the cable to hang between the two peaks of the bedforms. Under the actions of ocean currents and internal waves， the suspended section of the optical cable would generate vortex vibrations and even wear due to oscillatory motions with the seabed， so that the safe life of the optical cable would be shorten. Therefore， to determine reasonable length of cable laying is a very important task in the design of submarine optical cable engineering. This article explores the causes of submarine bedforms， the mechanism of cable damage on the bedform seabed， and analyzes the calculation method of cable laying length redundancy in order to provide references for the design of submarine optical cable engineering.