Fiber-optics

The most important feature is that fiber optics consists of plastic-coated cables. So the cables are insulators, they can be used to transfer signal between devices with separate grounds, or at different voltages. Moreover they do not act as antennas.

In case of a transmission over long distances, they are advantageous compared to coaxial cables, which are dispersive.

How to align single mode fiber

Among the essentials for obtaining optimal transmission through a fiber optic are having a good cleave and end polish, and, if free space coupling light into or out of the fiber, choosing the correct lens. Choosing a coupling optic for a multi-mode fiber is relatively simple. Select an optic whose numerical aperture (NA) is closest to matching that of the fiber. This will result in a focused spot size from the light source that is comparable to the core size of the fiber and whose incident cone angle does not exceed the arcsine of the NA of the fiber, which will allow for maximum coupling efficiency. For single mode fibers, selection of the appropriate coupling optic is a bit more complicated. In this case we need to determine the required focal length of the lens. From Gaussian optics, the equation used for this is given by $f=$

Intensity Modulation via FC/PC reflection

FC/PC connectors on both ends of the fiber patchcord acts as low-finesse cavity and produces intensity modulation while scanning the laser frequency. Use FC/APC connectors to mitigate this effect, e.g. instead FC/PC-FC/PC use FC/APC-FC/APC patch-cord