A Low-Voltage 35-GHz Silicon Photonic Modulator-Enabled 112-Gb/s Transmission System

Abstract

We present a silicon photonic traveling-wave Mach-Zehnder modulator operating near 1550 nm with a 3-dB bandwidth of 35 GHz. A detailed analysis of travelingwave electrode impedance, microwave loss, and phase velocity is presented. Small-and large-signal characterization of the device validates the design methodology. We further investigate the performance of the device in a short-reach transmission system. We report a successful 112-Gb/s transmission of four-level pulse amplitude modulation over 5 km of SMF using 2.2 V pÀp drive voltage. Digital signal processing is applied at the transmitter and receiver. 56-GBaud PAM-4 and 64-Gb/s PAM-2 transmission is demonstrated below a pre-FEC hard decision threshold of 4:4 Â 10 À3 .

Time-Domain Large-Signal Modeling of Traveling-Wave Modulators on SOI

“…10a. This discrepancy was also observed in others' works [12,14]. In the subsection of large-signal analysis, effects of this error on the extinction ratio of the modulator are investigated.…”

“…Coplanar waveguide (CPW) and coplanar strip (CPS) transmission line (TML) are commonly used as traveling-wave electrodes for high-speed modulators [11][12][13][14][15]. The CPS is considered in this case as our traveling wave electrode because of its compact geometry in comparison to CPW.…”

“…The CPS is considered in this case as our traveling wave electrode because of its compact geometry in comparison to CPW. To maximize the bandwidth of a TW modulator, the following should be respected: (1) mismatch between the optical group velocity and RF group velocity should be minimized; (2) characteristic impedance of the electrode loaded by p-n-junction should match the input and output impedance of RF ports, typically 50 Ω; and (3) modulator RF losses should be minimized [12,14].…”

“…The maximum unloaded microwave effective index, nRF,u achievable in a CPS transmission line on SOI, without slowing down RF, is around 2.4, much lower than no,g [12]. Because of the very low dispersion in a transmission line, the difference between RF phase velocity and RF group velocity is negligible [12,14]. Hence we focus on slowing the RF phase velocity to force nRF,L to approach no,g.…”

Design of a carrier-depletion Mach-Zehnder modulator in 250 nm silicon-on-insulator technology

“…Different doping profiles and concentrations are used. The pn-diode in the optical waveguide can be designed in vertical direction (Liao et al, 2007;Azadeh et al, 2015b), lateral direction (Samani et al, 2015;Tu et al, 2014;Wang et al, 2013) or with interdigitated doping patterns (Xu et al, 2012;Hao Xu et al, 2014;Giesecke et al, 2016). Some important figures of merit of the modulator and geometry dimensions of the published devices are presented in Table 1 and compared with the results of this work.…”