Up to single lane 200G optical interconnects with silicon photonic modulator


Studies involving ultra-high-speed optical interconnects have attracted significant attention of researchers. This can be attributed to the rapid technological advancement that has correspondingly led to the increasing need for efficient broadband services. To this note, the focus has majorly emphasized on the accommodation of 400GE and 800GE interface of data center interconnects. However, this involves a short reach data center interconnects that requires efficient intensity modulation.

Among the available data center interconnects solutions, silicon photonic modulators exhibit low power consumption, small footprint which distinguishes it from the other methods. In a recently published literature, the operation of silicon photonic modulators above the 100G high speed was carried out. Unfortunately, the limited bandwidths of silicon photonic modulators, ranging from 30-40Hz hinders the transmission of generated pulse amplitude modulation signals over long distances. Therefore, increased modulator bandwidth is highly desirable. Among the available bandwidth enhancement methods, multi-electrode Mach-Zehnder modulator and substrate removed traveling-wave Mach-Zehnder modulator are reported. However, disadvantages like phase alignments that requires further adjustments and increased fabrication costs have reduced their use. To this note, researchers have been looking for alternatives and have identified the operation of silicon traveling-wave Mach-Zehnder modulator at high baud rate as a promising solution.

Peking University researchers: Professor Fan Zhang and colleagues from the State Key Laboratory of Advanced Optical Communication Systems and Networks developed and investigated the efficiency of a silicon traveling-wave Mach-Zehnder modulator operating at high baud rate. They aimed at examining the optical interconnects at high speeds using a single lane bit rate of 200Gb/s. Their research work was just presented at the Optical Fiber Communications Conference 2019. OFC is the largest conference on optical communication. The paper was considered Post-deadline Paper and such status is only given to the top papers state of the art presented at the conference.

In brief, the research team employed a receiver-side digital signal processing technique consisting of post filter and maximum likelihood sequence detection (MLSD) to compensate for the bandwidth limitation from both the device and fiber chromatic dispersion induced power fading effect. In the experiment, they investigated the transmission performance of ultra-high-speed Nyquist-shaped 4-level and 6-level pulse amplitude modulation (PAM-4/6) signals based on a silicon travelling-wave Mach-Zehnder modulator with 3-dB bandwidth of 22.5 GHz.

The authors reported that with the help of post filter and MLSD, 200Gb/s (80 Gbaud) PAM-6 and 176 Gb/s (88 Gbaud) PAM-4 signals can be generated with bit error rate (BER) below 20% and 7% hard-decision forward error correction (HD-FEC) thresholds at back-to-back scenario, respectively. For 1-km fiber link, 176 Gb/s (88 Gbaud) PAM-4 signal can be successfully transmitted below the 20% HD-FEC threshold.

In summary, the Peking University researchers successfully recorded, for the first time, the highest single lane data rate of 200G for silicon photonic optical interconnects. They further demonstrated the significance of the integrated circuits geared towards specific applications in enhancing single lane 200G data center interconnects applications. In general, the study will pave way for the advancement of broadband services taking into account the changing future trends.

Up to single lane 200G optical interconnects with silicon photonic modulator - Advances in Engineering


Zhang, F., Zhu, Y., Yang, F., Zhang, L., Ruan, X., Li, Y., & Chen, Z. (2019). Up to single lane 200G optical interconnects with silicon photonic modulator. Optical Fiber Communications, Th4A.6.

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