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In this paper, we propose and demonstrate a blind chromatic dispersion (CD) estimation method based on fractional Fourier transformation (FrFT). Through numerical simulations, the proposed CD estimation method is shown to be robust against amplified spontaneous emission (ASE) noise and nonlinear interference. Only 2048 samples are required for reliable CD estimation for single carrier 28 GBaud DP-QPSK or 32 GBaud DP-16QAM signals and the standard deviation can be as low as 98.9 ps/nm and 103.6 ps/nm respectively. The feasibility of the proposed CD estimation method has been experimentally verified using 28 GBaud DP-QPSK and 14 GBaud DP-16QAM signals over various transmission distances with CD ranges of 46332 ps/nm ~ 77220 ps/nm and 5148 ps/nm ~ 51480 ps/nm respectively. Compared with some other CD estimation methods, the method based on FrFT has advantages in the aspects of less computation complexity and robustness to transmission impairments.

High spectral efficiency modulation format based unrepeatered transmission systems using distributed Raman amplifier (DRA) have attracted much attention recently. To enhance the reach and optimize system performance, careful design of DRA is required based on the analysis of various types of impairments and their balance. In this paper, we study various pump RIN induced distortions on high spectral efficiency modulation formats. The vector theory of both 1st and higher-order stimulated Raman scattering (SRS) effect using Jones-matrix formalism is presented. The pump RIN will induce three types of distortion on high spectral efficiency signals: intensity noise stemming from SRS, phase noise stemming from cross phase modulation (XPM), and polarization crosstalk stemming from cross polarization modulation (XPolM). An analytical model for the statistical property of relative phase noise (RPN) in higher order DRA without dealing with complex vector theory is derived. The impact of pump RIN induced impairments are analyzed in polarization-multiplexed (PM)-QPSK and PM-16QAM-based unrepeatered systems simulations using 1st, 2nd and 3rd-order forward pumped Raman amplifier. It is shown that at realistic RIN levels, negligible impairments will be induced to PM-QPSK signals in 1st and 2nd order DRA, while non-negligible impairments will occur in 3rd order case. PM-16QAM signals suffer more penalties compared to PM-QPSK with the same on-off gain where both 2nd and 3rd order DRA will cause non-negligible performance degradations. We also investigate the performance of digital signal processing (DSP) algorithms to mitigate such impairments.

Ba 0.6 Sr 0.4 Ti O 3 (BST) thin films were prepared on MgO buffered Pt(111)∕Ti∕SiO2∕Si substrates by pulsed laser deposition. The crystallographic structure, interface characteristics, and dielectric properties of BST thin films are strongly dependent on MgO thickness. BST thin films exhibit (111) preferred orientation when MgO layer is thicker than 5nm. The MgO layer can mitigate the interdiffusion between BST and Pt, causing the dielectric loss and leakage current of BST thin films to decrease significantly. The dielectric loss, tunability, and the largest figure of merit of BST thin films on 10nm MgO achieve 0.009, 30%, and 33.4, respectively.