Modbus optical isolators used with Modbus Plus

We have a client that has issues with high frequency noise damaging components connected to their Modbus Plus network. In searching for optical isolation devices I want to be sure that I don't have compatibility issues since many of the devices don't specifically say they are for Modbus Plus. If anyone can help me know what specifications to look at to determine that they will work, I would appreciate it. Also any experience with particular devices would be great. [email protected]

Thanks,
Mike