Making optical fibers more efficient

The research projects WESORAM and Multi-Cap aim to significantly increase efficiency in optical data transmission

Optical fibers already enable high-speed exchange of data. However, conventional fiber optic systems will no longer be powerful enough for future technologies such as autonomous driving. Two new research projects involving the Fraunhofer Institute for Applied Optics and Precision Engineering IOF are tackling the question of how the capacity of such fiber optic transmission systems can be significantly increased in the future.

It is the vein of the fast Internet: the optical glass fiber. But with the constantly growing amount of data, the existing fiber optic network will soon reach its limits. Experts estimate that data traffic on the World Wide Web will grow by more than 25 % annually in the long term. Particularly against the background of relevant future technologies - such as autonomous driving, 5G mobile technology, smart cities, or the Internet of Things - the performance of fiber optic networks must be further increased. Two new research projects in which Fraunhofer IOF is involved are currently addressing this challenge: the projects WESORAM and Multi-Cap.

Conventional fiber optic networks use fiber optic systems. Several parallel communication channels are realized in them via different frequencies or wavelengths. This allows multiple signals to be transmitted simultaneously in a single optical fiber while being assigned by wavelength, which corresponds to the color of the light. This is referred to as “wavelength division multiplexing”. However, this method can only be used in a limited frequency spectrum.

Multicore fiber.
© Fraunhofer IOF
Two new research projects have set themselves the goal of developing more powerful optical fibers. This should significantly increase data transmission in fiber optic systems in the future.

WESORAM develops new optical switches for wavelength selection

In order to overcome these limitations and to meet the growing requirements for transmission via optical fibers at the same time, new ways must be found. Further parallelization in optical data transmission can be a possibility here. It can significantly increase the capacity of optical networks because new types of optical fiber allow simultaneous propagation of waves of the same wavelength or frequency in several spatial transmission pathways. The familiar wavelength division multiplexing method is thus extended to a so-called “spatial division multiplexing” method. For fiber-optic transmission systems, this means a considerable increase in capacity.

In this context, the WESORAM project is dedicated to the development of a wavelength-selective switch for optical space division multiplexing. For this purpose, new optical switches are being developed for optical networks, which enable parallelization of the spatial channels.

Fraunhofer IOF contributes its know-how in the field of optical design as well as micro-optics to this project. A prototype is to be built at the institute by 2024. The optical design will first be implemented in Jena and then the optical components for the prototype will be built.

Multi-Cap aims to increase the efficiency of optical fibers using multicore fibers

Another dimension of multiplexing is the ability to transmit multiple channels spatially separated from each other in a single strand. This is where the Multi-Cap project comes in: With the aid of modern fiber technology, it is possible to incorporate multiple signal cores - i.e., transmission channels - into a single optical fiber. This is known as a “multicore fiber“. This not only saves significant space, but it also makes it possible to use additional components of the transmission link, such as amplifiers, only once instead of for each fiber individually. This enables significant energy and cost savings.

The aim of the Multi-Cap project is to investigate the limits of accuracy of optical parameters of multicore fibers in comparison with classic single-core fibers by 2024. In the long term, this should enable their use in telecommunications networks. In addition to an increase in capacity, energy savings of more than 20 % can be made possible through spatial multiplexing.

Fraunhofer IOF is involved in the project in both the fiber and laser technology aspects of these investigations. Design and fabrication of an optimized multicore fiber will be carried out at the institute.