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Fiber optic cables have found widespread use in the ocean, but to fulfill its mission the cable must survive deployment and operation scenarios. Preservation of the manufactured strength and the optical transmission capacity of the optical fiber over its application lifetime are the primary system objectives. Other secondary objectives defined by system requirements include: fiber count, flexibility, weight, strength, lifetime, manufacturability, diameter, specific gravity, torsion stiffness, temperature influence, pressure effects, abrasion, cyclic flexure resistance, to name a few. This paper will discuss fiber optic cables, causes of failures, and their materials for use in the ocean for three general classes: a. Low cost, disposable cables. This requires the replacement rather than the repair of subject cables. Several applications fall into this category namely torpedo guidance, rapidly dispensible acoustic systems, and sonobuoy links. Life expectancy is months. b. Moderate cost, replaceable cables. This class of cables also requires the replacement of the cable; however, the system lifetime requires the cable be manufactured with the best materials for ocean service so once it is deployed, survival is ensured for many months or even years. Once the cable has failed, there will be no attempt to repair or recover the product, only replace it. Again, this type of cable would see an environment that spans the ocean depths. c. High cost, repairable cables. This class of cables constitutes the family of cables that generally require many years of service, extremely high cable bandwidth (high fiber count), span the major ocean depths and service continents or nations for their communications needs. The starting point for any cable design is defining the requirements the cable must meet. A systems approach is used to derive and impose on the design those requirements that influence cable function, life, cost and transmission capacity. A system analyses defines the hazards a cable will see over its lifespan. Each cable must be designed with the needs of the customer in mind so that it can be produced at a reasonable cost.
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