This paper proposes new applications of a sinusoidally driven InGaAsP electroabsorption modulator to an inline optical gate for a 2R (reshape and retiming) repeater in optical amplifier systems, an n:1 optical demultiplexer in time division multiplexing systems, and an optical switching. Small polarization dependence of the modulator is essentially important for in-line use. By utilizing the monotonic increase of the extinction ratio with increasing the applied voltage, the electroabsorption modulator driven by large-signal sinusoidal voltage can produce a time domain square-shaped gate function with variable gate width. Furthermore, amplified spontaneous emission noise of optical amplifier systems can be reduced in both time and wavelength domains at off-state of the modulator, due to a noninterferometric wide wavelength operation of the modulator. Experimental results for a 2R repeater, an n:1 (n = 4, 8) optical demultiplexer, and optical gates for switching are also demonstrated for the first time at over 10-Gb/s repetition rate.
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