Optical Channel Impairments Mitigation on 40 Gb/s Systems Resorting to Post-Detection Adjustable Electrical Compensation

In this paper we present experimental results on a combination of a spectrally efficient optical modulation technique with post-detection electrical dispersion compensation, for reducing the effect of optical channel impairments on high-speed optical links. A description of the circuit topology of an adjustable electrical dispersion compensator (AEDC) prototype circuit is presented. Optical single-sideband (OSSB) modulation was used and results detailing electrical compensation of group velocity dispersion (GVD) and differential group delay (DGD) impairments are discussed. Our results show that, with this arrangement, a value of 18 ps of DGD and the joint effect of 12 ps of DGD and 272 ps/nm of GVD are compensated with close to 1 dB optical SNR (OSNR) penalty, in both cases to back-to-back measurement without compensation. If the AEDC is combined with a dispersive microstrip transmission line (DMTL) we achieve compensation of 374 ps/nm of GVD with less than 1 dB OSNR penalty and, considering the joint effect of 12 ps of DGD and 374 ps/nm of GVD, a value of 2 dB of OSNR penalty is measured. Additionally, we show that the AEDC can also mitigate the inter-symbol interference (ISI) due to optical signal bandwidth limitation. The use of the AEDC improves the optimum receiver noise-ISI tradeoff, or, equivalently, it allows a reduction of the optical filter bandwidth by 0.1 nm with no added penalty relatively to the case without filter.