FBG wavelength demodulation based on a radio frequency optical true time delay method.

Area of Science:

• Photonics and Optical Sensing
• Microwave Photonics
• Fiber Optic Sensors

Background:

• Fiber Bragg gratings (FBGs) are crucial for wavelength sensing.
• Accurate demodulation of FBG wavelength shifts is essential for various applications.
• Existing methods may face limitations in resolution or speed.

Purpose of the Study:

• To propose and experimentally validate a new FBG wavelength shift demodulation method.
• To leverage optical true time delay and microwave phase detection for enhanced resolution and speed.
• To investigate the impact of dispersion compensation fiber (DCF) and radio frequency (RF) signal parameters on measurement performance.

Main Methods:

• Utilized a microwave photonic link (MPL) to transmit an RF signal through a DCF.
• Exploited the chromatic dispersion of the DCF to induce time delay variations in the optical carrier due to FBG wavelength shifts.
• Employed an IQ mixer to measure the resulting RF signal phase variation for FBG demodulation.

Main Results:

• Achieved a wavelength shift measurement resolution of 2 pm under specific experimental conditions (79.5 ps/nm DCF GVD, 18 GHz RF frequency).
• Demonstrated a rapid demodulation time as short as 0.1 ms.
• Confirmed that higher RF frequencies, longer DCF, or larger DCF chromatic dispersion enhance measurement resolution.

Conclusions:

• The proposed optical true time delay microwave phase detection method offers a high-resolution and fast approach for FBG wavelength shift demodulation.
• The system's performance can be further optimized by adjusting RF signal frequency and DCF characteristics.
• This technique holds promise for advanced optical sensing applications requiring precise and swift measurements.