Highly integrated optical heterodyne phase-locked loop with phase/frequency detection

Area of Science:

• Photonics
• Integrated Optics
• Optical Communications

Background:

• Optical phase-locked loops (OPLLs) are crucial for coherent optical systems.
• Existing OPLLs often lack high integration and advanced functionalities.
• The need for compact and versatile optical frequency control is increasing.

Purpose of the Study:

• To propose and demonstrate a novel, highly-integrated optical phase-locked loop.
• To integrate key components onto a single photonic integrated circuit (PIC) and electronic IC (EIC).
• To achieve single-sideband heterodyne locking over a wide frequency range.

Main Methods:

• Design, fabrication, and testing of a photonic integrated circuit (PIC) on an InGaAsP/InP platform.
• Integration of a tunable sampled-grating distributed-Bragg-reflector laser, optical 90-degree hybrid, and photodetectors.
• Incorporation of a single-sideband mixer (SSBM) and digital phase/frequency detector in an electronic IC (EIC).

Main Results:

• Successful demonstration of a highly-integrated optical phase-locked loop for the first time.
• Achieved single-sideband heterodyne locking across a frequency range of -9 GHz to 7.5 GHz.
• Operated with a loop bandwidth of 400 MHz.

Conclusions:

• The developed PIC and EIC represent a significant advancement in integrated optical systems.
• This technology enables versatile and high-performance optical frequency control.
• The highly-integrated OPLL is suitable for advanced optical communication and signal processing applications.