The light used in fiber optic communication is visible light

Most fiber optic communication uses infrared light, which is not visible to the human eye.Fiber optic systems primarily transmit data using infrared light with wavelengths around 850 nm, 1300 nm, and 1550 nm, which are beyond the visible spectrum (400–700 nm) and therefore cannot be seen by humans . Infrared light is chosen because it experiences lower attenuation in glass fibers, allowing signals to travel longer distances with minimal loss . This makes it ideal for high-speed, long-distance telecommunications, including internet, telephone, and cable TV networks . While visible light, such as red light at 650 nm, can be used in short-range plastic optical fibers (typically under 50 meters), it suffers from higher signal loss and is not practical for most serious data transmission . Modern fiber systems, especially those using wavelength-division multiplexing (WDM), transmit multiple infrared wavelengths simultaneously, which are also invisible to the eye . It is important to note that looking directly into the end of a fiber optic cable is unsafe, even if the light is invisible, because the infrared laser can cause eye damage without any visible warning . Specialized equipment like fiber optic power meters is used to safely detect and measure the light signal. In summary, the light in standard fiber optic communication is generally invisible, with visible light only used in limited, short-distance applications. The choice of infrared ensures efficient, long-distance, and high-bandwidth data transmission while minimizing signal loss and interference.