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Various types of wavelength-selectable light sources (WSLs) and wavelength-tunable laser diodes (LDs) have been developed. and the one based on an array of distributed feedback (DFB) laser diodes (LDs) has the advantage of tuning that is both simple and stable timing. It requires only the selection of a DFB-LD and a temperature control. We report on monolithically integrated WSLs with a DFB-LD array, multimode interference (MMI) coupler, semiconductor optical amplifier (SOA), and electro-absorption (EA) modulator. To make them compact. we introduced microarray structures and to ensure that they were easy to fabricate, we used selective area growth. For the WSL with an integrated EA modulator, we developed a center-temperature-shift method that optimizes the detuning wavelength between the lasing wavelength and the absorption edge wavelength of the EA-modulator. Using this method, we obtained a uniform extinction ratio arid were able to demonstrate error-free 2.5-Gb/s transmission over a 600-km fiber span, A CW-WSL without an EA-modutator should provide enough output power to compensate the loss caused by the external modulators. but the high-power operation of a CW-WSL is sensitive to optical feedback from the front facet, We therefore used an angled facet in our WSLs and eliminated a mode hnp problem. More than 20 mW of fiber-coupled power was obtained over 23 ITU-T channels on a 50-GHz grid.