The role of long wavelength systems (1.0μm < λ < 10.0pm) in fiber optics communications is evaluated. For high-bit rate optical telecommunications at 1.3pm or 1.5μm, GaInAs p-i-n detectors have emerged as the preferred choice because of their low noise, excellent sensitivity, and high temperature stability. Ge and HgCdTe photodiodes offer nearly equivalent performance and a somewhat more advanced production technology. Beyond 2μm, HgCdTe would seem to be the clear choice for photodetector applications. Avalanche photodiodes in long wavelength optical fiber linksmay find uses in situations involving high bit-rate transmission using low-cost components. Although avalanche gain will always improve the system sensitivity, the LED4iPD combination is only half as sensitive as a laser/p-i-n system, as well as being bandwidth-limited. Non-telecommunications applications involving_ data-base and fiber-guidance systems are discussed and a prospective look is taken at the uses, such as power transmission, of ultra low-loss fibers in the 2 to 10μm region of the optical spectrum.