High-speed Multi-wavelength Photonic Switch
The ability to rapidly and independently switch multiple wavelengths in a light beam is useful for both WDM fiber-optic communications and for hardware compressed photonic signal processing. Key features for such a multi-wavelength switch include microsecond domain wavelength switching and excellent -50 dB optical switching isolation, leading to rapidly reconfigured
high signal-to-noise ratio photonic systems. Previously, the bulk acousto-optic tunable filter (AOTF) was found to be attractive for this multi-wavelength switch application as the bulk AOTF can operate over wide optical bandwidths with high speeds and at high optical power levels. Recent improvements in AOTF device designs have lowered the high drive power requirements commonly associated with bulk AOTFs. In addition, these new devices show spectral resolutions in the 1-nm. level range, indicating possible use for high (> 32) channel count WDM fiber communications. Nevertheless, one debilitating problem associated with the inherent operation of the AOTF is its finite (e.g., 95%) diffraction efficiency that leads to its low and undesirable -20 dB level type optical crosstalk numbers.
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