Mitigation of Dispersion Induced Impairments in Brillouin-based
Microwave Photonic Bandpass Filter
Abstract
Interference based microwave photonic bandpass filters (MPBF) form an
important component of modern RF signal processing. The presence of
multiple optical components in an RF photonic system e.g. fiber
amplifiers, waveguides, cause a degradation in the MPBF profile and the
out-of-band rejection due to the dispersion induced phase shift. Here,
we compare the performance, using simulations and experiments, of two
interference based MPBF configurations: (i) double-sideband phase
modulation (DSB-PM) and (ii) double-sideband intensity modulation
(DSB-IM), which exploit stimulated Brillouin scattering (SBS) for
sideband processing, under different dispersion conditions. While the
profile and out-of-band rejection for the DSB-PM based MPBF degrade
drastically under the effect of dispersion, DSB-IM based MPBF achieves
an out-of-band rejection of $>$ 40 dB and maintain the 3
dB and 20 dB bandwidths of 16.7 $\pm$ 0.4 MHz and 104.5
$\pm$ 5.4 MHz, respectively, under different dispersion
conditions. The DSB-IM based MPBF exploits the bias dependent phase of
the modulation sidebands of a z-cut intensity modulator to mitigate the
dispersion induced impairment. The use of an intensity modulator for
dispersion compensation makes our approach dynamic and compatible with
integrated microwave photonic systems.