Broad band optical amplifier using free space demultiplexing

A broad band optical amplifier (212) includes at least one free space wavelength demultiplexer/multiplexer (214) and optical gain means (222). The free space demultiplexer/multiplexer (214) receives a multiplexed signal (m- lambda ) and spatially separates it into a plurality of spectral components ( lambda -i) each having a unique peak wavelength. The optical gain means (222) has a plurality of wavelength-selective gain regions (224) that are capable of imparting gain to (i.e., amplifying) an optical signal over a particular narrow range of wavelengths. The operational range (i.e., the particular narrow range of wavelengths) of each gain region (224) is unique. The spatially-separated spectral components are individually delivered to specific gain regions by the demultiplexer/multiplexer as a function of the peak wavelength of the spectral component and the operative range of the gain region.