There is provided a fiber optic system comprising: a multi-wavelength source adapted to generate frequency modulated signals having different wavelengths, .lamda..sub.1, .lamda..sub.2, . . . , .lamda..sub.n; and an arrayed waveguide grating adapted to convert the multiplicity of frequency modulated signals into a multiplicity of substantially amplitude modulated signals, and spatially combine the different wavelengths .lamda..sub.1, .lamda..sub.2, . . . , .lamda..sub.n. And there is provided a method for transmitting an optical signal through a fiber comprising: operating a multi-wavelength source so as to generate frequency modulated signals having different wavelengths, .lamda..sub.1, .lamda..sub.2, . . . , .lamda..sub.n; passing the frequency modulated signals through an arrayed waveguide grating so as to convert the frequency modulated signals into substantially amplitude modulated signals, and spatially combine the different wavelengths .lamda..sub.1, .lamda..sub.2, . . . , .lamda..sub.n; and passing the substantially amplitude modulated signals into the fiber. And there is provided a fiber optic system comprising: a multi-wavelength source adapted to generate frequency modulated signals having different wavelengths, .lamda..sub.1, .lamda..sub.2, . . . , .lamda..sub.n; and a beam combiner adapted to spatially combine the signals having different wavelengths and pass them into a periodic optical spectrum reshaper (OSR) to generate a plurality of substantially amplitude modulated signals having wavelengths .lamda..sub.1, .lamda..sub.2, . . . , .lamda..sub.n.