Optimal Design For An Arrayed Waveguide Grating With Flattened Passband

Arrayed waveguide grating (AWG) is playing an increasingly important role in dense wavelength division multiplexing (DWDM) system. AWG provides a new dimension for solving capacity and flexibility problems in the telecommunication network. However, with the increase of channels, the conventional AWG requires better spectrum of lasers and insensitivity to the wavelength shift, the AWG with flattened passband can broaden these requirements.In the present thesis, the principle and structure of arrayed waveguide grating are introduced, the characteristic parameters of AWG are expatiated, and some methods that improve these characteristic parameters are analyzed and given. In order to obtain flatten passband, a multimode interferometer (MMI) is used to flatten the bandwidth of AWG and connected at the end of the input waveguide. However it results in larger ripple and deterioration of the on-chip insertion loss of AWG. So the present paper presents the following improved methods. A parabolic shape MMI is applied, and the ripple can be reduced by optimizing the width and length of the parabolic MMI. Moreover, a tapered waveguide is connected before the MMI, which reshapes the input field of MMI and decreases the loss resulting from mismatch of mode fields. Furthermore, a straight waveguide is added before the tapered waveguide to decrease distortion in mode fields, which results from the off centering of the peak field because of the bend of the input waveguides.According to the solution presented above, a novel AWG is implemented. Wide-angle beam propagation method (BPM) is used to simulate the improved layout. The ldB bandwidth of 64% and 3dB bandwidth of 78.8% are obtained for the 1000GHz channel spacing. Crosstalks to neighboring and all other channels are less than -30dB and the on-chip insertion losses range from -4.35dB to -5.0dB respectively.