In this gist you can find out how to fade in/fade out UIBlurEffect on UIVisualEffectView on iOS 10 and also earlier versions. Also added example ViewController to see how to use them in action. The below snippets are written in Swift3.

VisualEffectViewExtensions.swift

extension UIVisualEffectView {
  
    func fadeInEffect(_ style:UIBlurEffectStyle = .light, withDuration duration: TimeInterval = 1.0) {
        if #available(iOS 10.0, *) {
            let animator = UIViewPropertyAnimator(duration: duration, curve: .easeIn) {
                self.effect = UIBlurEffect(style: style)
            }
            
            animator.startAnimation()
        }else {
            // Fallback on earlier versions
            UIView.animate(withDuration: duration) {
                self.effect = UIBlurEffect(style: style)
            }
        }
    }
  
    func fadeOutEffect(withDuration duration: TimeInterval = 1.0) {
        if #available(iOS 10.0, *) {
            let animator = UIViewPropertyAnimator(duration: duration, curve: .linear) {
                self.effect = nil
            }
            
            animator.startAnimation()
            animator.fractionComplete = 1
        }else {
            // Fallback on earlier versions
            UIView.animate(withDuration: duration) {
                self.effect = nil
            }
        }
    }
  
}

extension UIView {
  
    func makeBlurEffectView(style:UIBlurEffectStyle? = nil) -> UIVisualEffectView{
        let blurEffectView = UIVisualEffectView()
        
        if let style = style {
            blurEffectView.effect = UIBlurEffect(style: style)
        }
        
        blurEffectView.frame = self.bounds
        blurEffectView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
        
        return blurEffectView
    }
    
    func addBlurEffectView(sendBack:Bool = false) -> UIVisualEffectView{
        let blurEffectView = makeBlurEffectView()
        self.addSubview(blurEffectView)
        
        if sendBack {
            self.sendSubview(toBack: blurEffectView)
        }
        
        return blurEffectView
    }
}

class SamplePopupViewController: UIViewController {
    
    var blurEffectView:UIVisualEffectView?
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        blurEffectView = self.view.addBlurEffectView(sendBack: true)
    }
    
    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        
        self.blurEffectView?.fadeInEffect()
    }
    
    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)
        
        self.blurEffectView?.fadeOutEffect()
    }
}