By employing auxiliary waveguides between the exit ends of arrayed waveguides, we experimentally demonstrate a SiON-Based cyclic arrayed waveguide grating router (AWGR) with 7 input and 7 output channels (7×7) and 400 GHz channel gap, to improve the loss uniformity. The field distribution at the image plane of the output free propagation region is adjusted by the auxiliary waveguides, in the other words, a flat-top shape can be obtained at the image plane by optimizing the parameters. The measured loss non-uniformity of the AWGR with auxiliary waveguides improves from 2.09 dB to 0.76 dB for the central input channel and from 1.99 dB to 0.88 dB for the edge input channel compared to the conventional AWGR. The minimum insertion loss of the central channel increases from 2.99 dB to 3.82 dB, and that of the edge channel increases from 4.83 dB to 5.46 dB. The crosstalk of all the channels is approximately 18 dB.