Fig. 1. Top-view optical micrographs of the WDM receiver chip, AWG, and Ge-on-Si waveguide photodetector array.

Fig. 2. (a) Typical I-V curves of the standalone photodetector with/without light incidence (1550 nm) from 1 V to −3  V. The optical power entering the photodetector is about −9.4  dBm. The inset is a schematic of the optical coupling in this measurement. (b) Spectral responsivity of the standalone photodetector from 1530 to 1580 nm under −1  V.

Fig. 3. Frequency response of a standalone photodetector at various reverse biases.

Fig. 4. (a) Photocurrent spectrum of each channel of the WDM receiver chip. The inset is a schematic of the optical coupling in this measurement. (b) Transmission spectra of the 25-channel 200 GHz AWG.

Fig. 5. 40 Gbps and 50 Gbps eye diagrams of channels 5, 10, 15, 20, and 25 at 0 and −1 V. The modulator eye diagrams are also shown for comparison.

Fig. 6. BER curves of channel 10 at 40 and 50 Gbps. The 40 and 50 Gbps eye diagrams of channel 10 under −2.4 and −2.2  dBm input optical power are shown for comparison.