Dec 14 (Thu) @ 10:00am - "Integrated Electronics for Energy-Efficient Coherent Optical Communication," Ghazal Movaghar, ECE PhD Defense

Date and Time
Engineering Science Building (ESB), Room 2001


Emerging cloud-based applications have resulted in a significant growth in data center traffic. Majority of the total data center traffic is attributed to short-range (< 1 km) data center interconnects (DCI) and these short-range links demand continual scaling in spectral efficiency, bandwidth (BW), and latency. To address this growth, DCIs will operate at bit rates (BR) above 200 Gbps per wavelength with high efficiency. The simplicity and low cost of intensity-modulation direct detection (IMDD) have prevailed for short-range fiber optic links. Nevertheless, coherent detection offers additional scalability to multiple amplitude levels by changing both the phase and amplitude of the signal. Moreover, coherent could provide vastly more link budget and dynamic range for optical packet switching, an emerging technology to improve data centers efficiency.

The focus of this talk is the development of energy-efficient coherent optical communication links through exploring the system architecture, as well as integrated opto-electrical circuit design. Design procedure to optimize power consumption for the desired bit rate is presented. Based on the optimization, a 1310-nm (O-band) coherent optical Link is demonstrated that operates to 56-GBd symbol rate (SR)(112 Gbps). The coherent optical receiver (CORX) leverages a monolithic 45-nm CMOS SOI photonic-enabled process to realize an energy-efficient quadrature phase shift keying (QPSK) demodulation. Co-design of the optical and electronic circuit elements supports high-speed operation and low power consumption. The coherent link is demonstrated with an optical transmitter photonic IC (PIC) fabricated in a silicon photonic (SiPh) process with laser diodes wirebonded to a 90-nm SiGe driver electronic RFIC. The transmitter operates at 5.9-pJ/bit energy efficiency (EE) while the receiver achieves 0.73 pJ/bit. The implementation shows promising results to enable high-speed O-band coherent links with optimized energy efficiency for future intra-data center networks.


Ghazal Movaghar received her B.Sc degree in Electrical Engineering from Sharif University of Technology in 2018 and M.S.c degree from University of California, Santa Barbara where she is currently pursuing her Ph.D in Electronics and Photonics under supervision of Prof. Buckwalter. Her current research focuses on design and integration of electronic and photonic ICs for high speed, low power optical communication.

Hosted by: Prof. James Buckwalter

Submitted by: Ghazal Movaghar <>