An all-optical logic NOT gate is a basic building block for implementation of all-optical shift registers, packet header processing, bit-error monitoring etc. A passive NOT gate based on spectral phase-only linear optical filtering of an input return to zero on-off-keying (RZ-OOK) data signal was first proposed and demonstrated in . This gate requires no energy for switching and it is compatible with ultrafast speed processing. In , a commercial waveshaper was used to implement the needed spectral phase-only filter. However, commercial waveshapers are bulky, expensive and offer a limited frequency resolution (> 10 GHz), which in turn imposes a severe constraint on the minimum bit rate of the data signals (typically above 640 Gb/s for random data). To this end, we propose a fibre Bragg grating (FBG) design to achieve narrow spectral phase filters for NOT gate operation of RZ-OOK data. In the design reported here, we assume an incoming data signal at 80 Gbps with a PRBS of 27-1 bits and 5-ps FWHM Gaussian pulses.
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