Help for count an optocuplor on arduino

Other Hardware Sensors
3

Hi and thanks for yout answer.
I'm not an electronist.
I think it is an analog sensor not a digital one , because if i connect it to a digital pin it doesn't send anything.If i connect on an analog pin it send some value, if it doesn't have any object into optocuplor it send me a 36 alternate 37 values. if i put something into optocuplor it send me values greate than 100.
My code is a simple cod for read an analog pin, because first i want to know what sensor send and after this i need to count it:
int sensorPin = A8;
int sensorValue = 0;

void setup()
{
pinMode(sensorPin , INPUT);
Serial.begin(9600);
}

void loop()
{
sensorValue = analogRead(sensorPin);
Serial.println(delay(sensorValue);
}
Many thanks.