The chip is a low-power, ultra-compact, fully-differential 40 Gb/s direct detection receiver fabricated in 0.25 µm Photonic BiCMOS SiGe technology. This design effectively utilizes the advantages of Electronic-Photonic Integrated Circuits (EPIC) technology platforms, such as allowing for very short interconnects between the photodiode and the amplifier.

The novel architecture integrates a fully-differential input stage, automatic photodiode biasing, and DC coupling between the diode and the Transimpedance Amplifier (TIA). Crucially, the photodiode is connected directly to the inputs and is biased internally around -1V, requiring no external bias components. This approach, which relies on the inherent symmetry of the photodiode rather than utilizing replica diodes or AC coupling components, helps to minimize noise, input capacitance, and overall area.

The receiver boasts an extremely small footprint. The overall size of the chip is only 600 µm by 450 µm, covering an area of 0.27 mm². The electronic core occupies just 280 µm × 200 µm. The small area is achieved in part by routing a 420 µm taper, which connects the grating coupler to the waveguide, underneath the bond pads.

Measurements demonstrated a limiting performance up to 40 Gb/s with well-opened eye diagrams. The electronic core consumes only 120 mW of power from a single supply. Due to its compact, inductorless, and fully-differential topology, the chip exhibits a high power supply rejection ratio, making it particularly well suited for multi-channel direct detection receivers.

References

S. Gudyriev, J. C. Scheytt, L. Yan, C. Meuer and L. Zimmermann, "Fully-differential, DC-coupled, self-biased, monolithically-integrated optical receiver in 0.25μm photonic BiCMOS Technology for multi-channel fiber links," 2017 IEEE Bipolar/BiCMOS Circuits and Technology Meeting (BCTM), Miami, FL, USA, 2017, pp. 110-113.

S. Gudyriev et al., "Low-power, ultra-compact, fully-differential 40Gbps direct detection receiver in 0.25μm photonic BiCMOS SiGe technology," 2016 IEEE 13th International Conference on Group IV Photonics (GFP), Shanghai, China, 2016, pp. 178-179.