Optical fiber cables transmit information using pulses of light, typically infrared or visible, which are modulated to carry digital data.

Nature of Optical Signals

Optical fiber cables send light signals rather than electrical signals, using either laser diodes or LEDs as transmitters to generate the light . These light pulses represent digital information, where the presence or absence of a pulse corresponds to binary "1" or "0" in digital communication . The light travels through the fiber core by total internal reflection, confined by the cladding with a slightly lower refractive index . This allows the signal to propagate over long distances with minimal loss and interference.

Modulation and Transmission

The light in optical fibers is modulated to encode information. Common modulation methods include intensity modulation, where the brightness of the light varies to represent data, and wavelength-division multiplexing (WDM), which sends multiple light wavelengths simultaneously through a single fiber to increase capacity . Single-mode fibers carry light in a straight path for long-distance transmission, while multi-mode fibers allow multiple paths or modes, suitable for shorter distances .

Advantages of Optical Signals

Optical signals in fiber cables offer high bandwidth, low attenuation, and immunity to electromagnetic interference, making them ideal for transmitting voice, video, internet data, and telemetry over long distances . They can achieve extremely high data rates, with modern systems capable of tens of gigabits per second per channel . Additionally, the use of light makes interception more difficult, enhancing security compared to electrical signals. In summary, optical fiber cables send pulses of light that are modulated to carry digital information, enabling fast, reliable, and high-capacity communication across telecommunications networks and other applications .