Wavelength-selectable microarray light sources for wideband DWDM

Tunable/selectable-wavelength light sources are now beginning to play important roles in dense wavelength-division multiplexing (DWDM) optical transmission systems. Among the many types of the light sources, we have been developing distributed-feedback (DFB) laser-diode (LD)-array-based 'wavelength-selectable' light sources (WSLs), because of their stable and reliable wavelength properties. This paper reviews our recent progress with WSLs devices and WSL modules for wide-band DWDM applications. We start by describing eight DFB-array WSLs, each of which has a tunable wavelength range (Dl) of 15 nm. We took full advantage of an advanced form of selective metal-organic-vapor-phase epitaxy, which we call microarray selective epitaxy (MASE), in fabricating WSLs of six types on two wafers to fully cover the S-, C-, and L-bands. These WSLs demonstrated high fiber output power of up to around 10 mW and had stable single-mode properties. We also describe a 94-channel (50-GHz spacing) WSL module with an integrated multi-wavelength-locker. A wide-band WSL with a Dl of 40 nm for the L-band, was installed with a compact wavelength locker in a standard-sized 22-pin butterfly package. The WSL module showed a stable locking performance of within a 1-GHz range over time and against variations in temperature.