In optical communication systems, fiber gratings have been used to perform chromatic dispersion compensation, gain equalization, pulse compression, soliton pulse shaping, add/drop switching and channel filtering for wavelength division multiplexing (WDM) systems [1,2]. Recently Chen et al. studied a multiple grating structure that could be used to achieve spectral slicing in WDM and CDMA systems [3]. In this paper we propose a tunable multiple-grating fiber for frequency-hop encoding-decoding operations. To our knowledge, this is the first proposal for frequency-hop code division multiple access (FH-CDMA) in optical fiber local area networks.