Which of the following is used to define the waveform of an optical signal?

The waveform of an optical signal is fundamentally defined by its wavelength. Wavelength is a critical parameter in optics that describes the distance between successive peaks or troughs of a wave. It is directly related to how light propagates and interacts with different materials, influencing various optical properties such as dispersion, reflection, and refraction.

In the context of optical signals, variations in wavelength can affect how information is transmitted through optical fibers, signal quality, and bandwidth. Each wavelength corresponds to a specific frequency, but it is the wavelength itself that relates directly to the shape and characteristics of the optical waveform.

While frequency and phase are also relevant in describing aspects of waveforms, they do not specifically define the shape of the optical signal in the same way that wavelength does. Voltage is primarily applicable to electrical signals, not optical ones. Thus, wavelength is the key parameter that defines the waveform of an optical signal.