Optocoupler - Make active low output at active high
Yes. Swap the positions of the 1.6 k&Omega; resistor and the opto-transistor. That will default to pull-down and the opto-isolator will pull up.

It's not clear why you're using the opto-isolator other than as an inverter (which you seem to not want) since you have CH connected to the micro-controller's D7 so you have lost all isolation.

Your CH1, if it's a 5 V input, should be fed directly from D7, not from the top of the infrared LED where it will be clamped by the 1.4 V forward voltage, Vf of the infrared LED.