Measuring LPO (Low-Pulse Occupancy)
You can trigger on CHANGE, and check in your handler which case it is:

   attachInterrupt(digitalPinToInterrupt(my_pin), my_handler, CHANGE);
    (...)
    void my_handler(void) {
      if(LOW==digitalRead(my_pin)) {
        //do_falling();
      }
      else {
        //do_rising();
      }
    }


Another option would be to use a timer to poll your input, and implement a logic on top of this.