• Use of optical control for light path switching in the development of a novel optical switching system
• Fabrication of an optical switch delivering to multi port with optical fiber connection and verification of its operational performance
• Achieving a micro-second response speed by utilizing the high-speed thermal lens effect of stacked layer-type organic thin-film optical elements
• Ease of verifying the signal/control light wavelengths (achievable by changing the pigments used for the element)
• Potential for customizing the response speed to match specific applications

 

The Photonics Research Institute at the National Institute of Advanced Industrial Science and Technology ("AIST") has been successful, in collaboration with Dainichiseika Color & Chemicals Mfg. Co., Ltd., in developing a device ("optical switch") capable of separating the incident signal light from the optical fibers directly, without conversion to the corresponding electrical signals, under optical control and of outputting these optical signals to other multiple optical fibers. The separation of the signal light under optical control is achievable by utilizing the high-speed thermal lens effect generated in a thin-film element by applying the control light to a stacked layer-type organic thin-film optical element. This system is capable of separating the incident light at micro-second speed. Since, furthermore, light is also used for switching control, this development marks a technical breakthrough toward the realization of an "exclusively photonic optical switch," a technology recognized as essential for the next generation photonic network.

The micro-electro-mechanical system (MEMS) and the planar light circuit (PLC) being developed for practical use are mechanically operated and require heating with electrical heaters of considerable capacity. With these system it is therefore difficult to achieve significantly higher switching speeds. A great number of other systems has also been

proposed, but their merits are canceled out by their demerits, seeing that it is difficult to find an acceptable balance between their switching speed and their extinction rate.

The realization of light path switching under optical control opens up a significant potential for data transmission and switching that is more resistant to electrical noise, and can thus make a major contribution in economic and social terms. The development of this technology is therefore of major importance as it has technically not been possible until the present to achieve light path switching under optical control.

AIST has taken up this challenge by developing an "optical switch using a refraction system based on a thermal lens" to achieve a fast switching speed by minimizing the focusing spot size, with the possibility of securing a high extinction ratio. To achieve a high refraction effect, use has been made of a stacked layer-type organic thin film optical element, consisting of an array in which a film containing pigments is dissolved or dispersed in a low thermal conductivity polymer or organic solvent sandwiched between high thermal conductivity glass layers, using a coaxial light entrance system for the signal and control light. By varying the types of pigment it is also possible to cover a wide range of wavelengths. It is possible, furthermore, to vary the response speed by tuning the element structure. (A response speed of several tens of micro-seconds can be achieved for semi-fixed switching.)

The development schedule for the near future is to achieve greater miniaturization and lower costs by using a micro-lens, for example, and to synthesize multiple signal wavelengths with the light path switching by sending the signal light and the control light for light path switching through the same optical fibers.