Intensity-modulation and direct-detection (IM/DD) orthogonal frequency division multiplexing (OFDM) systems have gained great attentions from researchers. However, the interaction between the chirp of direct modulation laser and fiber dispersion causes intermixing interferences among sub-carriers. Therefore, in this paper, we adopt Volterra filter to reduce the intermixing interferences and improve the BER performance in IM/DD OFDM systems. We first introduce the basic concept of Volterra filter and then set up simulation systems. The simulation results show that the system has a good BER performance by using a Volterra filter. This research provides a theoretical guidance for the information transmission in power grid.

Flocculation water treatment is one of the important aspects of water treatment .The aim of this work is to use PFS for treating Yellow River surface water and different molecular weights of chitosan as coagulant aid. Electron microscope was used to observe flocs morphology and study CTS coagulation aid morphological change, floc image with microscope camera system analysis, calculation of floc fractal dimension. The results show that the different molecular weights of CTS in dealing with surface raw water to play a good coagulation aid effect. Microscope and image analysis system of flocs morphology show that fractal dimension of morphology of PFS / CTS were significantly higher ,Among them，high molecular weight of CTS as coagulant aid，and fractal dimension of morphology of PFS/ CTS were 1.1026,1.5593 , low molecular weight of CTS as coagulant aid，and fractal dimension of morphology of PFS/ CTS were 1.0904,1.5440 respectively. Floc fractal dimension changes to better reflect the flocculation level and treatment effect for the establishment of floc fractal dimension number of changes in the coagulation control is provided for reference.

The aim of this work is to remove residual turbidity and index of Potassium permanganate of the drinking water by PAC/Chitosan coagulation treatment. The experiments were performd the efficiency of coagulation by PAC/Chitosan at different chitosan dosages , molecular weight and pH value. Zeta potential instrument and Nikon electron microscope were used to test Zeta potential and observe flocs morphology. It turn out that Chitosan enhance the flocculation treatment of the surface water of raw water of Yellow River by polymeric aluminum chloride (PAC)when PAC dosage is 35 mg•l-1 and Chitosan is 0.15 mg•l-1 and infer coagulation aid mechanism was interpartical bridging rather than the electrical neutralization. Microscope and image analysis system of flocs morphology show that fractal dimension of morphology of PAC and PAC/Chitosan were 1.294,1.385, respectively.