How is digital modulation defined in optics?

Digital modulation in optics refers to the manipulation of light waves in a specific, controlled manner to convey information. This typically involves encoding data by varying light intensity, phase, or frequency in a predefined sequence. Specifically, the interruption of light waves in a coded sequence effectively allows the transmission of digital signals, facilitating communication through optical mediums such as fiber optics.

The process makes it possible to represent binary data as variations in light, which can be transmitted over distances with high fidelity and speed. This method is crucial in modern communication technologies where digital data needs to be converted into optical signals for transmission, making it possible to achieve efficient data transfer.

Other options do not accurately reflect the concept of digital modulation in optics. Continuous change in light frequency doesn't encapsulate the coding aspect essential for conveying binary information, constant light emission lacks the modulation characteristic entirely, and a combination of light frequencies does not imply the necessary interruption or sequence vital for digital signaling.