DWDM intra-cavity laser device

A tunable Dense Wavelength Division Multiplex (DWDM) intra cavity laser device comprising:

• a first optical wave guide comprising a first optical grating section,
• a second optical wave guide comprising a second optical grating section, an active gain section spatially separated from the second optical grating section and a phase section,
• a DWDM-filter comprising an intra-cavity ring resonator located between the first optical wave guide and the second optical wave guide for coupling optical waves between the first and second optical wave guides,
• wherein a length of the ring resonator is selected such that the free spectral range of the ring resonator matches a wavelength spacing of a predetermined fixed wavelength spacing grid,
• wherein the tunable laser device is tunable in a discrete manner in that wherein at least one of the first optical grating section, the second optical grating section and the phase section are tunable for fine-tuning the optical wavelength so as to switch, in discrete fixed wavelength-spacing-steps, between two or more channels inside the predetermined fixed wavelength spacing grid to which the ring resonator is matched, and
• wherein the first optical grating section and the second optical grating section are mutually tunable for providing a Vernier effect for switching between the two or more channels.