Abstract: In accordance with the invention, the fabrication of a grating phase mask is improved by providing a multiple-scan exposure which can provide an accumulated exposure that is effectively phase modulated or modulated rapidly in amplitude. Applicants have determined that exposure scans can be chosen so that each is modulated in amplitude and without modulation in phase, but the accumulated exposure of the multiple scans is modulated in phase and/or modulated in amplitude. The improved method can be used to make phase masks for fabrication of sophisticated fiber gratings such as superstructure gratings.

Abstract: In accordance with the invention, an optical fiber communication system comprising a source of optical signal channels and an optical fiber transmission line is provided with one or more single source, multiple-order Raman pumps downstream of the source. Each single source pump provides multiple-order Raman pump light for amplifying the signal channels.