Liquid crystal switching boosts optical communications

13 Mar 2013

Fraunhofer IPMS demos fiber-optic-coupled LC switch with two states; on show at OFC-NFOEC 2013.

Novel optical switches and modulators based on electro-optical waveguides induced in special liquid crystal arrangements have been developed by the Fraunhofer Institute for Photonic Microsystems IPMS, Dresden, Germany.

Liquid crystals are ideal for such applications because they are especially sensitive to electrical fields, exhibit short response times on the submicron scale and feature excellent transparency over a broad spectral range, from visible to infrared.

Fraunhofer IPMS says that the potential for the technology goes well beyond optical telecommunication networks. The R&D center will introduce this innovative technology to the public in Anaheim, California during the OFC/NFOEC 2013 expo, a leading trade show for fiber optic communication technologies.

At the show, Fraunhofer IPMS will introduce two new innovative liquid crystal waveguide based demonstrators designed for switching and modulating of optical signals. Visitors will have the opportunity to get an in-depth look at the technology, which is demonstrated with a bidirectional fiber-optic coupled 1×2 switch, in which visible light is employed to permit the direct visualization of the underlying switching process. The institute will also introduce a fiber-optic coupled modulator operating at the telecommunication wavelength.

'Great potential'

Dr. Michael Scholles, Head of Business Development & Strategy at IPMS, says, “The potential for transmitting large amounts of data using fiber optic networks appears to have no boundaries: high bandwidth, multi-terabit per second speeds and optical loss so low that it requires amplification of the signal on the line only at sites located far apart. However, this potential can only be exploited when the network bandwidth is fully utilized.

”This potential can be achieved by merging, separating, amplifying and attenuating various fiber-optic signals, which are all extremely demanding techniques. The optical switches or multiplexers employed in these environments must be fast and reliable, permit a high number of switching cycles, have multi-channel capability, low insertion loss and crosstalk, and be flexible enough for integration together with other components.”

To address these issues, researchers at Fraunhofer IPMS developed the promising optical switch concept based on electro-optically induced waveguides in liquid crystals [“EOIW’].

How it works

Technology development manager Dr. Florenta Costache explained, “Large anisotropies are induced in a special liquid crystal layer within a limited region by locally applying an external electrical field. This allows a light wave to be precisely guided in this specific region. Optical loss of only 0.5 dB/cm is achieved with this guiding technique.

”The devices' fast switching speeds of below one microsecond as well as megahertz modulation frequencies arise from our use of the liquid crystals' electro-optic Kerr response to electrical fields. Although the components were developed for the 1550 nm telecommunication wavelength, if desired they can be adapted for any wavelength within the visible to infrared part [400 to 1600 nm] of the spectrum”.

She added, “The components are manufactured using planar silicon technology, which allows cost-effective, high-volume production. The switch features a straightforward design that provides key advantages with respect to the stability and reliability of the switching process and the simple integration with other components. For this reason, the Fraunhofer IPMS EOIW technology is far from limited to applications in optical communication networks.”

”Our switching and modulation technology can be implemented in any complex optical system for applications such as data transfer and processing, fiber optic sensor systems and laser technologies or security. What our electro-optical switches do here is selectively direct the individual channels for cyclical analysis in the interrogation instruments.”

Further developments concerning this technology are currently funded by the German Federal Ministry of Education and Research in the project Electro-Optical Waveguides based on Liquid Crystals for Integrated Optical Circuits. The project EOF-IOS, which will last for two years, is part of the research initiative Wissenschaftliche Vorprojekte (WiVorPro) within the programme of Photonic Research in Germany.

The Fraunhofer IPMS will be exhibiting at booth 2657 in the Anaheim Conventional Center.

About the Author

Matthew Peach is a contributing editor to optics.org.