When you work or deal with cables which contain optical fiber, you probably noticed designations like “FIMT”, “FIST”, “SST” or maybe other abbreviations which are related to a fiber optic cable. But what do those abbreviations stand for exactly and what is the meaning behind these terms?
The most popular word in the industry definitely is “FIMT” and stands for: Fiber In Metal Tube. Meaning a stainless-steel tube, which is filled with fiber optics either for telecommunication purposes or for high-tech sensing functions. Such a FIMT can come in many different designs which differs in material grade, dimensions and filling compound, but also in different FIMT cable constructions with several independent layers. The main purpose having a stainless-steel housing for the optical fibers is to protect all these fragile components against mechanical and environmental influences. Imagine, a bare optical fiber is implemented in downhole applications, where the environmental is aggressive in terms of heavy chemical influences as well as high hydrostatical pressure or bending and torsion, such a fiber would neither survive the deployment procedure. For this reason, different designs containing stainless steel tubes are necessary to ensure a safe and long-time job for such applications which can be very different from project to project.
FIMT = Fiber In Metal Tube
FIST = Fiber In Steel Tube
SST = Stainless Steel Tube