High Number Of Pixels Research Articles

100-GHz-resolution dynamic holographic channel management for WDM

We present results that demonstrate the active management of eight /spl sim/100-GHz-spaced wavelength-division-multiplexed (WDM) channels using a polarization-insensitive spatial-light-modulator-based holographic filter. The filter has a fundamental stepping resolution close to 25 GHz and 3-dB width of each individual passband equal to 42 GHz. Arbitrary permutations of dropped and passed channels are possible. Additionally, passed channels can be transmitted according to an equal-amplitude comb filter function or be transmitted with weighted-amplitude passbands to effect power equalization where necessary. The holographic technique is further extendable to passband spectral engineering, yielding near-rectangular top hat passbands. Suppression of the dropped channels, which is consistently >15 dB in these experiments, can be straightforwardly improved by deploying a spatial light modulator of greater resolution and higher pixel number. The technology has potential application as the key element in both an optical add-drop multiplexer and a dynamic multichannel equalizer. The passband 3-dB width can be straightforwardly reduced to allow processing of multiple channels at the 50-GHz spacing of future WDM systems.

The extended Fourier algorithm: Application in discrete optics and electron holography

The conventional discrete Fourier transform can be extended to a discrete Extended Fourier transform (EFT). The EFT allows to work with discrete data in close analogy to the optical bench, where continuous data are processed. The EFT includes a capability to increase or decrease the resolution in Fourier space (thus the argument that CCD cameras with a higher number of pixels to increase the resolution in Fourier space is no longer valid). Fourier transforms may also be shifted with arbitrary increments, which is important in electron holography. Still, the analogy between the optical bench and discrete optics on a computer is limited by the Nyquist limit. In this abstract we discuss the capability with the EFT to change the initial sampling ratesiof a recorded or simulated image to any other(final) sampling rate sf.