Single-mode fiber: From research and development to manufacturing

Single-mode lightwave has completely replaced multimode as the technology of choice for long-haul, metropolitan interoffice, and subscriber loop systems. This article discusses the design principles and performance of four kinds of single-mode fibers developed by AT&T Bell Laboratories. AT&T Technologies has shipped over a thousand megameters of a fiber (in cable form) optimized for 1310-nm systems. This fiber is known as a depressed-cladding single-mode fiber, because of its refractive-index profile. It was designed to provide low intrinsic loss, high bandwidth, low splice loss, and a high resistance to macrobending- and microbending-induced losses. Three other fibers that offer new possibilities to system designers are: dispersion-shifted fiber that is optimized for 1550-nm systems; dispersion-flattened fiber that has high bandwidth over a wide wavelength range; and polarization-maintaining fiber that can be used with phase-sensitive receivers.