We present a detailed description and a first theoretical study of an improved concept for high-frequency self-pulsations (SPs) in multisection (MS)-DFB lasers with an integrated phase tuning section. The DFB wavelengths of the two DFB sections are spectrally detuned by nearly the stopband width using two gratings with different grating periods. If both DFB sections are operated at lasing conditions and an appropriate phase is chosen, we obtain beating-type SP with a frequency given by the spectral distance of two lasing modes. Good agreement between theory and experiment is obtained with respect to the role of the detuning, the role of the phase section, as well as the synchronization to external injected signals. The modeling shows a strong nonlinear coupling of the two involved modes via the carrier densities. This effect is important for the mutual coherence and for the observed locking of the beating oscillations to external signals. From the results of the calculations, we draw the conclusion that even higher SP frequencies can be obtained based on the new concept

An all-optical clock recovery module is developed and tested in a 100 Gbit/s 105 km transmission experiment. A penalty free function of the optical clock relative to an electronic phase-locked loop is demonstrated. The compact module is wavelength and polarisation insensitive and requires no electrical radiofrequency equipment. Continuous frequency tuning from 5 to 22 GHz indicates the potential for bit rate flexible clock recovery

A first demonstration of a 40 Gbit/s all optical clock recovery module based on a design for a novel self-pulsating DFB laser is presented. The role of detuned gratings in the new device concept is evaluated and experimental results of self-pulsation at 40 GHz are reported. The successful locking to 40 Gbit/s optical data signals emphasises the future application in an all-optical 3R-regenerator

An analysis of the threshold behavior of long-wavelength ( lambda =1.55 mu m) multiquantum well separate-confinement lasers with InGaAs wells and quaternary ( lambda g=1.3 mu m) barriers is presented. Using the effective mass approximation and Fermi statistics for carriers, an approximately logarithmic dependence of optical gain on carrier density for quantum well lasers with one confined electron state is predicted theoretically. This prediction is verified by measured threshold currents of broad-area lasers of various cavity lengths and different numbers of quantum wells. Moreover, the characteristic parameters, such as transparency current density, gain constant, and absorption outside the active region, are determined

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