how to send data to 15 meters with KY-005
In the emitter breakout board there is only a LED, nothing more. Comments in the linked page of the supplier states, that the 5V pin of it is not connected to anything. This means you are driving the LED directly from the Arduinos pin, which cannot provide more than 40mA. The supplier states a forward current from 30 to 60mA. You can use a small MOSFET in combination with a resistor, that limits the current to maybe 55mA, to drive the LED indirectly.

With this you won't fry the pins hardware and can provide more current, which means the LED can shine brighter. If you can find out, what LED is actually used for this board, you can refer directly to its datasheet. I couldn't find a part number at the site.