“We believe that this integration approach could be used to achieve 200 GBaud transmission with a silicon photonic modulator.”~ Researchers.
Researchers at University of Southampton in the UK recently developed a transmitter based on complementary metal-oxide-semiconductor (CMOS) technology and silicon photonics. They have achieved increased data rates along with energy efficiency by co-designing the electrical driver amplifier and optical modulator inside the device.
The new technology is an all-silicon optical transmitter that integrates 28 nm bulk CMOS technology with silicon photonics. It is capable of achieving high-speed data transmission, hitting rates of 112 gigabaud (GBd), which translates to 112 gigabits per second using on-off keying (OOK) modulation, and doubling that rate to 224 gigabits per second when utilizing pulse-amplitude modulation with four levels (PAM-4).
The team has explored the boundaries of power consumption at these high transmission rates, successfully demonstrating that energy efficiency can be achieved below one picojoule per bit. Remarkably, this level of efficiency is attained without resorting to traditional methods like pre-emphasis or signal shaping at the data source, which are commonly used to enhance signal integrity.
One of the critical challenges addressed is the balance between minimizing the power consumption of the driver amplifier and maintaining an acceptable signal-to-noise ratio (SNR), which is vital for preserving the bit error rate (BER) within an acceptable range. A lower power draw from the driver amplifier typically has the adverse effect of degrading the SNR, thus potentially increasing the BER.
To navigate this trade-off, the researchers have conducted experimental analyses of the full transceiver link, assessing the relationship between the electrical energy efficiency and the average received optical power. This investigation is key to optimizing the design and operation of optical transmitters for high-speed, energy-efficient communication systems.