Low-complexity coherent optical receivers

Abdelrahman, Ahmed

Permalink

https://hdl.handle.net/2142/127487 Copy

Description

Title

Low-complexity coherent optical receivers

Author(s)

Abdelrahman, Ahmed

Issue Date

2024-12-04

Director of Research (if dissertation) or Advisor (if thesis)

Hanumolu, Pavan Kumar

Doctoral Committee Chair(s)

Hanumolu, Pavan Kumar

Committee Member(s)

• Shanbhag, Naresh R.
• Rosenbaum, Elyse
• Schutt-Aine, Jose E.

Department of Study

Electrical & Computer Eng

Discipline

Electrical & Computer Engr

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Coherent Optical Receivers
• Wireline
• Serial Links
• Transceivers
• SerDes

Abstract

The rapid growth of data-intensive applications in data centers has driven the demand for high-speed, energy-efficient optical interconnects. Traditional intensity-modulation direct-detection (IM-DD) techniques face significant challenges in scaling data rates, making coherent detection a promising alternative for short-reach links. Coherent detection offers higher spectral efficiency by utilizing intensity, phase, and polarization but comes with increased power consumption due to the need for advanced digital signal processing (DSP) engines. This dissertation explores analog signal processing (ASP) techniques for designing low-complexity, power-efficient coherent optical receivers (RXs) tailored for short-reach data center interconnects (DCIs). By minimizing the reliance on power-hungry analog-to-digital converters (ADCs) and complex DSP algorithms, the proposed designs enable more energy-efficient operation. The first part of this work introduces a monolithically integrated, wide-bandwidth, analog carrier-phase recovery (CPR) loop for QPSK coherent RXs, that eliminates the need for external optical feedback loops, enhances phase tracking capabilities and reduces system complexity. Fabricated using a 28 nm CMOS process, the QPSK RX achieves error-free operation at 24 Gb/s, with 10–100 MHz CPR loop bandwidth and 600 MHz frequency tracking range, consuming only 3.2 pJ/bit. The second part extends the QPSK RX and CPR architectures to support 16-QAM formats, addressing the complexities of higher-order modulation. A novel phase detector (PD) design is proposed, leveraging both inner and outer symbols for improved phase tracking of 16-QAM constellations. The 16-QAM RX, also fabricated in a 28 nm CMOS, achieves a bit error ratio (BER) of 1E-10 at 64 Gb/s, with 20 MHz CPR loop bandwidth, while consuming just 1.54 pJ/bit. These innovations highlight the potential for scalable, low-power coherent optical RXs and pave the way for broader adoption of coherent technology in short-reach data center applications.

Graduation Semester

2024-12

Type of Resource

Thesis

Handle URL

https://hdl.handle.net/2142/127487

Copyright and License Information

Copyright 2024 Ahmed Abdelrahman

Owning Collections