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Translating Bands of Light

‘Translating’ Bands of Light

Most of the data traveling through optical fiber around the world is transported on bands of light of a standard infrared wavelength. The 1.55-micron wavelength is ideal for telecommunications because it is where glass fiber is most transparent and efficient. But other existing or planned applications, ranging from airborne and submarine communications to biomedical lasers and remote sensing, operate at different wavelengths (and different colors of light). And there’s the rub: most of the equipment for generating, transporting and detecting optical signals was developed for the telecom market and cannot handle light at wavelengths other than 1.55 microns.

But Jacobs School electrical and computer engineering professor Stojan Radic has demonstrated a novel method for efficiently “translating” optical signals within the fiber between the infrared standard and other bands of light. With a team including ECE professors Shaya Fainman and Joseph Ford, Radic used a parametric process (i.e., a process that does no damage to the photonic crystal fiber) to change the wavelengths of modulated optical channels by as much as 1 micron from infrared to visible light. Further, the before-and-after difference in frequency— 375 terahertz—was a factor of ten greater than previously achieved.

Radic is now working on converting infrared to other useful wavelengths. “A parametric band translator means that mature telecom technology can be applied to any other wavelength,” says Radic. “This will permit development of new applications at various bands without requiring huge investment in new infrastructure to replace what already exists.”