Fiber Optic Cables do not need coils except to make it easy for cable makers to sell a single model of cable that can be stretched to fit the needs of different photographers.
Otherwise, Cables with Coils can get caught on outside objects and pulled off, they flop around and are a nuisance. I learned this the hard way while diving when one of my coiled cables was inadvertently kicked off, and lost, by the dive guide.
Another important drawback to coils is that they double or more the length of the cable, thereby significantly cutting down the amount of light that reaches the strobe.
Coiling requires heating the cable, as in hot water, and heating is well known to "cook" the optic fiber, making it opaque and markedly reducing the light transmitted. Both the added cable length and the reduced light may explain why some strobes such as the Sea&Sea are said not to fire consistently with coiled fiber optic cables.
Coiling requires a thin cable, and thin cables break easily, two or three of mine have broken, like brittle spaghetti, during daily use.
In contrast, thicker cables with no coils, ie, Toslink, in my experience have always triggered Inon and Sea&Sea strobes of several models, have not gotten caught on external objects nor interfered with the taking of photos.
To ensure one has a cable sufficiently long for other, longer strobe arms, it is easy to make it long enough so one can thread or wind the cable around the arms being used, and to add one or more wraps for the spare length.
It is important to use Toslink of 3 or 4 mm o.d. as it is much tougher than the 1 or 1.5 mm cable, and transmits much more light, at almost no additional cost. These thicker cables do not break, in my experience.
In brief, to fire a strobe from an underwater housings, a short, thick, un-coiled straight fiber optic cable is much tougher, and carries much more light than a long, thin, coiled cable. It always fires the strobe, is inexpensive, dependable and easy to make, with few if any problems.
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