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We demonstrate optical Nyquist channel generation based on a comb-based optical tapped-delay-line. The frequency lines of an optical frequency comb are used as the taps of the optical tapped-delay-line to perform a finite-impulse response (FIR) filter function. A single optical nonlinear element is utilized to multiplex the taps and form the Nyquist signal. The tunablity of the approach over the baud rate and modulation format is shown. Optical signal-to-noise ratio penalty of 2.8 dB is measured for the 11-tap Nyquist filtering of 32-Gbaud QPSK signal.

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We demonstrate optical true time delays using wavelength conversion coupled with chromatic dispersion. The transfer function of the delay system is investigated, and it is shown that 3-dB bandwidth of the system can be increased over 40 GHz by using offset pumps. A flat magnitude response (<1 dB peak-peak, 0.2 dB RMS deviation) is achieved in the 1-30 GHz band. Calculated matched filter output to LFM pulses shows good performance, maintaining a > 30 dB peak-to-sidelobe-ratio. The effect of pump depletion during wavelength conversion is also investigated.

We demonstrate a reconfigurable optical transmitter of higher-order modulation formats including pulse-amplitude-modulation (PAM) signals and quadrature-amplitude-modulation (QAM) signals. We generated six different modulation formats by multiplexing 10 Gbit/s on-off-keying (OOK) signals (10 Gbaud binary phase-shift keying, 4-PAM, 8-PAM quadrature phase-shift keying (QPSK), 16-QAM and 16-star-QAM with error-vector magnitudes (EVMs) of 8.1%, 7.5%, 7.8%, 8.2%, 7.2%, and 6.9%, respectively) and 80 Gbit/s 16-QAM with an EVM of 8.5%, as well as 120 Gbit/s 64-QAM with an EVM of 7.1%, using two or three 40 Gbit/s QPSK signals, respectively. We also successfully transmitted the generated 16-QAM signals through a 100 km transmission line with negligible power penalty.

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