Laser light is used for optical fiber communications for the simple reason that it is a single wavelength light source. Sunlight or the light emitted by a light bulb is a mixture of many different wavelengths of light. Because the light waves of such light are all out of phase with one another, they do not produce a very powerful beam. Laser beams, however, have a single wavelength, and so their waves are all in phase, producing very powerful light. The speed of light traveling along an optical fiber changes in accordance with its wavelength. Because ordinary light contains many different wavelengths of light, differences emerge in speed of transmission, reducing the number of signals that can be transmitted in any set time. Being a single wavelength light source with uniform phase, laser light travels smoothly with very little dispersion, making it ideal for long distance communications.