New optical filtering technique to result in fatter pipes RRS feed

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  • New optical filtering technique to result in fatter pipes

    2/15/2007 9:41:51 AM, by Chris Lee

    In last month's Nature, Photonics reported a nice combination of an old optical telecommunications trick with new photonic technologies. in doing so the researchers who performed the work have opened the door to using these new devices in standard telecommunications networks.

    Optical communications achieves very high data rates through a combination of fast modulation of a single channel (around 10Gbps) and running multiple channels down the same fiber. Each channel is a slightly different wavelength (color), so the maximum bandwidth depends on how closely these channels can be spaced. The minimum channel spacing is set by the ability to separate light of different wavelengths.

    New photonic devices, such as the microtoroid pictured at left, are very good at separating and combining very closely spaced channels. For any particular device, however, the performance depends on the polarization of the light, which is the spatial orientation of the electric and magnetic fields. This is undesirable because normal fiber optic cable randomizes the polarization of light.

    Researchers took advantage of a property of polarization, that light of any polarization is really a combination of two light beams of different brightness and polarized at right angles to each other. The researchers split the incoming, randomly polarized, light into two beams with well-defined orthogonal polarizations. These two beams were then transported to two slightly different microrings, each optimized to act as an add-drop filter for that particular polarization. The new signal, with one channel removed and a different channel added, is then recombined into the original randomly polarized light, which can then be directed back into a fiber optic cable.

    This trick is currently used in fiber-based optical isolators and circulators. However, the combination of this trick with microrings is very cool and will eventually lead to narrower channel spacings and hence fatter pipes. It is not, however, the huge breakthrough that some technology journalists seem to think it is.

    Wish somebody found it helpful.BTW haven't seen such a discussion lacking forum in a while.

    Thursday, February 15, 2007 5:05 PM