Wavelength control for fibre-grating lasers enables low-cost DWDM operation down to 25 GHz channel spacing

We present a new, very cost-efficient control scheme to stabilise the mode and the emitted wavelength of fibre-grating lasers. It permits us to maintain the wavelength constant within /spl plusmn/5 pm while the output power may vary between -4 and +4 dBm. Such wavelength stability is a key requirement for dense wavelength-division multiplex (DWDM) systems, and we demonstrate its suitability down to 25 GHz channel spacings. The control scheme is based solely on the power at the laser's back facet, which is monitored with a photodiode. Therefore, this control scheme drastically reduces the complexity and cost of DWDM laser sources.