The volume of data transmitted over optical networks is constantly increasing, requiring operators to increase the capacity of their networks. Typically, this includes adding new channels (adding a new wavelength) or shrinking the time between light pulses (signaling faster).
Because a pulse broadens with the distance it travels due to dispersion, it begins to overlap with the neighboring pulse. The receiver needs to identify individual pulses, so the overlap should not be too large.
Additionally, as the pulse travels, it loses intensity due to attenuation - the signal gets weaker. The quality of the fiber link is determined by its signal to noise ratio. It is beneficial to reduce the noise, and/or increase the signal power. The higher the launching power, the longer the distance the signal can travel before it is attenuated too much to be detected. However, there are limits to the launching power. If it the power density is too high, nonlinear effects can occur that prevent a longer reach.
When new fiber networks are designed, fibers with reduced attenuation characteristics or with a larger core (that can cope with higher launching power) or with both properties can be selected.
Attenuation is influenced by a multitude of parameters. The purity of the glass is one parameter that influences attenuation. Fiber producers have reduced the germanium content in the core to reduce attenuation. As a refractive index difference between core and cladding is the essence of an optical fiber, these fibers rely on cladding with reduced refractive index relative to pure silica. Heraeus supports these designs with fluorine-doped tubes.
Additional factors that influence attenuation are the surface quality of potential interfaces in the preform (micro-bending loss) and fiber draw conditions (stress), to name a few. Heraeus supports the drive for lower attenuation by offering high purity fused silica tubes with an excellent surface quality for core rod production as well as precisely machined fused silica cylinders for the RIC process.
More information on fused silica tubes and cylinders
More information on the RIC® process