Typically no, you cannot control volume through optical cables. Since optical cables are designed to transmit pulses of lights digitally, and to maximise the signal to noise ratio the light pulse is usually set to maximum intensity. And if you use this light intensity to control the volume of any audio system, then you’ll actually reduce the volume down by 5% and the signal will start becoming noisy and distorted. The only way to control volume through optical cable is to make sure you have digitally intelligent devices at both ends of the cable. This means that the transmitter and the receiver should be aptly able to receive and decode the signal to adjust the amplified volume.