Abstract
We demonstrate an optical transmitter consisting of a limiting SiGe BiCMOS driver co-designed and co-packaged with a silicon photonic segmented traveling-wave Mach-Zehnder modulator (MZM). The MZM is split into two traveling-wave segments to increase the bandwidth and to allow a 2-bit DAC functionality. Two limiting driver channels are used to drive these segments, allowing both NRZ and PAM4 signal generation in the optical domain. The voltage swing as well as the peaking of the driver output are tunable, hence the PAM4 signal levels can be tuned and possible bandwidth limitations of the MZM segments can be partially alleviated. Generation of 50 Gbaud and 53 Gbaud PAM4 yields a TDECQ of 2.8 and 3.8 dB with a power efficiency of 3.9 and 3.6 pJ/bit, respectively; this is the best reported efficiency for co-packaged silicon transmitters for short-reach datacenter interconnects at these data rates. With this work, we show the potential of limiting drivers and segmented traveling-wave modulators in 400G capable short-reach optical interconnects.
Highlights
The ever-rising growth of the internet and its associated applications have pushed datacenters to deploy optical transceivers with continuously increasing performance
We demonstrate an optical transmitter consisting of a limiting SiGe BiCMOS driver co-designed and co-packaged with a silicon photonic segmented traveling-wave Mach-Zehnder modulator (MZM)
We demonstrate a transmitter consisting of a segmented traveling-wave silicon MZM wirebonded to a custom designed SiGe BiCMOS driver chip
Summary
The ever-rising growth of the internet and its associated applications have pushed datacenters to deploy optical transceivers with continuously increasing performance. Standards employing 53.125 Gbaud PAM4 up to 2 and 10 km SMF are being developed [2]. Designing transceivers at 53 Gbaud proves to be a challenging task: low power, small footprint and manufacturability are key factors in the design. Transmitters based on silicon photonic modulators are very attractive since they offer low cost, high volume and high yield manufacturability of devices. Several silicon photonic PAM4 transmitters have already been shown [3,4,5]. While microring modulators and electro-absorption modulators may offer smaller footprints and a lower power consumption [3,4] compared to Mach-Zehnder modulators (MZMs), both have a limited optical bandwidth and introduce chirp which limits the fiber reach. Silicon photonic coherent transceivers (requiring MZMs) are already being deployed by industry [6]
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