CONCERNING NUMBERS

One encounters an extreme range of numbers in the fiber optics business. For example, a high-speed data link may respond in the picosecond range while a low-speed RS-232 link may respond in the millisecond range. To understand fiber optics and much of electronics, one must be familiar with the prefixes used to express these numbers. For example, deep red light at one end of the visible spectrum has a wavelength of 700 nanometers (nm) which is 700 billionths of a meter or 0.00002756 inches. Deep violet visible light has a wavelength roughly half of red's: 350 nm or 0.00001378 inches. Wavelengths of light are given in small numbers. If, however, we express light as a frequency, we get a large number. Deep red has a frequency of 430 THz or 430,000,000,000,000 Hz. Violet's frequency is 850 THz or 850,000,000,000,000 Hz.

Syst me Internationale or SI Units, more commonly referred to as the metric system, use prefixes to express large and small numbers. The following prefixes are used most.