Fast wavelength-switching of laser transmitters and amplifiers

The authors discuss system aspects and describe experimental demonstrations of nanosecond wavelength tuning in laser diode structures. Both tunable transmitters and tunable filters are considered. The dependence of the refractive index on the carrier density in semiconductors is exploited to obtain fast wavelength tuning. Experimentally, switching times of <15 ns have been demonstrated in a three-section distributed Bragg reflector (DBR) laser transmitter with a maximum continuous tuning range of 2.2 nm. These conditions correspond to a system with 50 wavelength-addressable channels. A new scheme for simultaneous wavelength-switching and data modulation, which alleviates wavelength drifts due to thermal effects, is presented. Distributed feedback (DFB) laser structures biased below the lasing threshold operate as resonant tunable amplifiers. A uniform DFB laser amplifier has been demonstrated with a 1 ns wavelength-switching time. Experiments with tunable transmitters and tunable filters that simulate their operation in packet switching systems including both wavelength-switching and data modulation, are also described.<
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