Real-time frequency-to-time mapping based on spectrally-discrete chromatic dispersion

Area of Science:

• Photonics
• Optical Signal Processing
• Fourier Transforms

Background:

• Traditional photonics-assisted real-time Fourier transform (RTFT) faces challenges with limited dispersion, large size, and signal loss.
• Existing methods struggle to achieve high sensitivity and real-time processing efficiently.

Purpose of the Study:

• To propose and demonstrate a novel frequency-to-time mapping (FTM) technique for enhanced real-time Fourier transform.
• To overcome the limitations of conventional RTFT systems by utilizing spectrally-discrete dispersion.

Main Methods:

• A novel medium with periodic intensity response and quadratic phase distribution is proposed for de-chirping optical input.
• The method employs discrete phase retardation instead of continuous true time delay for compact, high-dispersion devices.
• Implementation is suggested using cascaded optical ring resonators.

Main Results:

• A proof-of-concept experiment demonstrated FTM with a 400-MHz unambiguous bandwidth and 25-MHz resolution.
• Achieved a highly sensitive and linear mapping of 6.25 ps/MHz, equivalent to ~4.6 × 10^4 km of standard single-mode fiber.
• The compact device achieved real-time FTM within each period.

Conclusions:

• The proposed FTM method offers a promising solution for real-time, low-latency Fourier transform applications.
• Cascading optical ring resonators can further extend the instantaneous bandwidth.
• This technique significantly enhances frequency sensitivity and overcomes traditional RTFT limitations.