Fast axis is a term used to describe the specific orientation of a fiber optic cable within a birefringent material. The term is used to describe the orientation of the cable in relation to the direction of the lightwave’s vibration, in which the index of refraction is lowest. For a fiber optic cable, the fast axis is the primary axis in which light is transmitted through the cable.
The fast axis is determined by the direction of polarization of the lightwave, which is the process of the lightwave’s oscillations being confined to one plane of the wave. This direction is the fast axis, and the direction perpendicular to this is the slow axis. When the lightwave travels through a fiber optic cable, it passes through the cladding and core of the fiber, where it is refracted by the index of refraction in each medium.
In the case of a birefringent material, the index of refraction will vary depending on the direction of the lightwave’s vibration. The direction with the lowest refractive index is the fast axis, while the direction with the highest index is the slow axis. This is important to the performance of the cable, as the lower the refractive index, the faster the light will be able to travel through the cable.
When installing a fiber optic cable, it is important to ensure that the fast axis of the cable is properly aligned. Misaligning the cable can cause a decrease in the speed of light transmission, as well as an increase in signal loss due to increased refraction. If the cable is misaligned, it is important to realign it so that the fast axis is in the correct direction. By doing this, the performance of the cable will be improved, and data can be transmitted more quickly and reliably.