Coherent transmission using an external waveguide Bragg reflector laser with direct frequency modulation

Abstract

Single-frequency l.5μm semiconductor lasers, formed by butt-coupling of a regular Fabry—Perot laser to an external waveguide Bragg reflector, are shown to have very uniform frequency modulation characteristics under direct current modulation. The laser's frequency modulation characteristics, together with its narrow linewidth (̃ 1 MHz), make coherent transmission possible without external modulators. The laser performance was evaluated in a 417Mbit/s, 102 km, frequency-shift-keying coherent transmission experiment.