Unable to visualise PointCloud in Rviz (ROS) from publisher and subscriber node

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I am using the below code for publisher and subscriber. I am able to visualise PointCloud on Rviz for input node but failed to visualise output node. As i am quite new in ROS. How i can solve the problem? I have even set in Rviz the Fixed Frame: base_link.

   ros::Subscriber subPointCloud;
    ros::Publisher pubPointCloud;

    void DEM(const sensor_msgs::PointCloud2ConstPtr& input)
    {
      ROS_DEBUG("Point Cloud Received");
      pcl::PointCloud<pcl::PointXYZ>::Ptr cloud (new pcl::PointCloud<pcl::PointXYZ>);
      sensor_msgs::PointCloud2 output;

      // Convert from ROS message to PCL point cloud
      pcl::fromROSMsg(*input, *cloud);
      pcl::toROSMsg(*cloud, output);

      output.header.stamp = ros::Time::now();
      output.header.frame_id = "/base_link";
      pubPointCloud.publish(output);

      }


    int main(int argc, char** argv)
    {
      ROS_INFO("Starting LIDAR Node");
      ros::init(argc, argv, "kitti_lidar_node");
      ros::NodeHandle nh;

      subPointCloud = nh.subscribe<sensor_msgs::PointCloud2>("input", 1, DEM);
      pubPointCloud = nh.advertise<pcl::PointCloud<pcl::PointXYZ> > ("output", 1);

      ros::spin();

      return 0;
    }