volatile unsigned PulseTime = 0;

void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
  analogWrite(10,255/2);
  noInterrupts();
  TCNT1=0;
  TIFR1=0;
  TCCR1B|=(1<<CS10);
  TCCR1B|=(1<<ICES1);
  TIMSK1|=(1<<ICIE1);
  interrupts();
}

void loop() {
  // put your main code here, to run repeatedly:
  unsigned pulseTime=0;
  noInterrupts();
  pulseTime=0;
  interrupts();

  if(pulseTime){
    Serial.println(pulseTime);
  }
}

ISR(TIMER1_CAPT_vect){
    static unsigned RisingEdgeTime = 0;
    static unsigned FallingEdgeTime = 0;
    if(TCCR1B&(1<<ICES1)){
      RisingEdgeTime = ICR1;
      TCCR1B&=~(1<<ICES1);
    }
    else{
      FallingEdgeTime=ICR1;
      TCCR1B|=(1<<ICES1);
      PulseTime = FallingEdgeTime - RisingEdgeTime;
    }
  }