To replace DFB lasers in wavelength-division-multiplexing (WDM) systems, tunable lasers should provide the same output power (20 mW) and remain simple devices, We propose a two-section DBR laser with optimized design. The required settings to reach all the achievable ITU wavelengths with constant output power are simply derived from very few initial characterizations. We obtain a record 20-mW coupled output power, constant over 16 am (= 40 channels 50-GHz spaced). For the first time, power performances comparable with DFB lasers are obtained; DBR lasers are now competitive candidates for an integration in WDM systems.

A new wavelength-division multiplexed (WDM) optimized design of integrated electroabsorption modulator distributed feedback lasers provides a great tolerance on operating conditions and laser wavelength: 2.5 gbit/s transmission over 1000 km is performed for /spl Delta/I/sub laser/=70 mA, /spl Delta/T/sub chip/=20/spl deg/C, and /spl Delta//spl lambda//sub laser/=10 nm.

A wide-bandwidth on-chip mirror based on a deeply etched Bragg grating localized over 10 mu m is presented; it exhibits reflectivity over more than 25 nm. Integration within a laser-Mach-Zehnder modulator is shown and the wavelength-division multiplexing capability of the device demonstrated in a hybrid Bragg reflector configuration, by showing operation of the same InP chip with fiber gratings from 1534 to 1558 am.

The performances of electroabsorption (EA) modulators integrated with a DFB laser (EA-DFB) are limited by optical feedback and chirp characteristics. Moreover, these devices are very sensitive to the operating conditions due to their very sharp characteristics. We report a new EA-DFB design that totally suppresses optical feedback and shows very smooth characteristics. Transmission over 1000 km of standard dispersion fiber is achieved reproducibly with V/sub "on level"/=0 V (P/sub ave/=2 dBm), over a large range of operating conditions (laser current: 50-120 mA, temperature: 15/spl deg/-35/spl deg/C, laser wavelength: 1550 /spl plusmn/5 nn). This is a very attractive source for easy-to-implement long-haul WDM systems.

A 40 GHz pulse source module at 1.55 /spl mu/m has been realized with an integrated MQW DFB laser/electroabsorption modulator: 6 ps pulse width, with 12 dB dynamic extinction ratio has been obtained with low driving voltage.

The characteristics of 25 integrated laser-modulator devices compatible with 10 Gbit/s NRZ transmission over 90 km of standard fiber are presented. Mean performances and their standard deviation are discussed showing the reproducibility of the results.

Ridge integrated laser modulator (ILM) devices were fabricated using a butt-coupling technology based on two-gas-source molecular-beam epitaxy, A complete stability evaluation was undertaken, including a reliability study on discrete lasers, discrete modulators, and integrated devices, High temperature, high current, and high voltage were applied for over 1900 h without significant evolution of the electrooptical characteristics. A functional aging test at the current corresponding to a 2-mW output power and the modulator bias necessary to reach the maximum extinction ratio was performed for more than 1500 h, The butt-coupling region does not affect the reliability of the integrated devices.

Results are reported for a repeaterless transmission experiment at 2.5 Gbit/s through 1391 km of non-dispersion-shifted fibre (26100 ps/nm total chromatic dispersion), using a module incorporating an integrated electroabsorption (EA) modulator/DFB laser chip. A system penalty of 0.2 dB was obtained producing a record bit-rate-distance product of 3.5 Tbitkm/s.

To fully utilize the high bandwidth of single-mode optical fibers, many new system architectures have been proposed. One particularly attractive scheme is wavelength-division multiplexing (WDM), which, in addition, brings flexibility to the communication network.

In the present paper, we describe a laser halographic system to fabricate frst-order gratings with pitches from 190 to 250 nm, over the entire surface of 2 in epitaxial wafers. We present an operating procedure allowing good control of parameters that determine the mark/space ratio. The corrugation uniformity is measured by a mapping grating efficiency system. By using a buried guiding layer, we achieve good control of the coupling coefficient. An improvement of the fabrication yield for devices is shown by means of distributed feedback laser diodes results.

Measurements of subthreshold spectra on SCMQW (separate-confinement multiquantum-well) lasers with the number of wells varying from three to nine have led to the determination of the carrier-induced differential refractive index d mu /dN approximately -3.6*10/sup -20/. This value is 1.8 greater than in the case of conventional bulk lasers. This study allows for a better understanding of quantum well laser parameters such as the spectral linewidth enhancement factor. It is also useful for the design of tunable lasers.< >