connect a PWM output to a differential or photocoupler input of a PLC

Hello all,
I have a PWM output 100mA, 50 Ohm from a CMOS driver. I want to connect it to a pulse input of a input/output card of a PLC. The pulse inputs are differential input (5V) and photocoupler input (5V). Any suggestion on how I should connect them? The pulse inputs to the PLC require 3 wires: pulse -, pule + and pulse input ground. The PWM output is a BNC female connector.
Thank you for your help.

The optical isolator shown on this page does an excellent job of differential to single-ended conversion. Though usually used with encoders it provides three channels of conversion.