No, you would not be able to see light when looking down an optical cable from one side to another if there is no light source transmitting at that time between both sides. Optical cables are designed to transmit light signals, typically in the form of pulses of laser or LED light. If there is no light being transmitted through the cable, there would be no visible light to see.
Optical cables are typically made of materials with high reflectivity, such as glass or plastic, which helps to guide the light signals along the cable by repeatedly reflecting them internally. This design prevents light from escaping the cable and ensures that the signals reach their intended destination. Without an active light source sending signals, the cable would appear dark when viewed from either end.