All-optical fast fourier transform for processing an optical OFDM superchannel

This paper presents an experimental and simulated demonstration of an all optical fast Fourier transform (FFT), based on optical interferometry, applied for the dropping of an optical orthogonal frequency division multiplexing (OFDM) carrier. The OFDM signal, comprising an aggregate rate of 75 Gb/s quadrature phase shift keying (QPSK) modulation, was generated from an optical comb, with 12.5 GHz channel spacing, provided by the gain-switching of a semiconductor laser. The experimental results were then used to calibrate a system simulator where an all-optical Inverse FFT was included for the adding of an optical OFDM carrier. A synchronism mechanism was also configured in the simulation setup. The obtained bit error rate (BER) performance below the forward error corrector (FEC) limit for both, experimental and simulated, implementations, demonstrate the node architecture feasability for the optical processing of a superchannel with carrier spectral overlapping.