The main-to-sidelobe suppression ratio (MSSR) is significant to filters. The tap weight errors worsen the MSSR of the finite impulse response (FIR) microwave photonic filters (MPFs). The MSSR can be improved by shaping the multicarrier optical source spectra with high precision. By compensating the errors with an iteration method, the sidelobes of the amplitude response can be optimized to increase the MSSR. Such a method is simple, effective, and compatible with all FIR MPF approaches. In the experiment, optical spectra of Gaussian profiles were taken as an example, and an MSSR improvement from 50 to 63 dB was demonstrated.
A novel 2-bit PDAC based on quadrature phase modulation and differential demodulation together with balanced
detection is proposed and experimentally demonstrated at sampling rates of 2.5GS/s and 10GS/s. The simulation results
of expanded 4-bit PDAC from the 2-bit PDAC unit by using two channels of incoherent light with different wavelength
are presented. This PDAC scheme is simple, compact and effective with high expansibility. Compared with other
approaches, this method's output signal has a greater dynamic range and a higher noise margin.
The proposed clock recovery scheme introduces electrooptical modulation to down convert the clock frequency
facilitating succeeding narrow band filtering by a phase locked loop (PLL) with ordinary radio frequency (RF) devices,
further, employs a quadrature phase detector in the PLL to provide an indication signal for monitoring residual
dispersion. It was demonstrated in a polarization multiplexed 160-Gbit/s optical non-return to zero quadrature phase
shift keying (NRZ-QPSK) transmission system.