Precise frequency stabilisation by dithering bias current of directly modulated laser-diodes

A frequency monitoring/stabilisation technique for dense wavelength division multiplexing access networks is proposed. To achieve more precise frequency stabilisation, the bias current used to drive each directly modulated LD is dithered. The key techniques are adding an offset bias to the detected error signal and offsetting the centre frequency of the arrayed waveguide grating port against the grid frequency to achieve effective frequency stabilisation. Experiments show that the relative frequency deviation of plusmn30 GHz can be suppressed to less than plusmn1 GHz without any BER degradation.