Optical heterodyne FSK system experiment with Brillouin amplifier is demonstrated using a CW pump of a DFB-LD operating at the 1.54µm wavelength. The 30 Mbit/s coherent FSK signal is amplified by 4 dB through 52 km single-mode fiber when the pump power of 2.5 mW is injected into the fiber. To obtain the flat gain profile ranging over the signal bandwidth, Brillouin gain bandwidth is broadened by means of modulating the pump frequency. Bit-error-rate performance is improved to reduce the rate by a factor of ten with the amplifier. Brillouin amplifier is useful for transmission systems at a bit-rate of less than 1 Gbit/s, as opposed to a fiber Raman amplifier.
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