Waveform measurement technique for phase/frequency-modulated lights based on self-heterodyne interferometry.

Area of Science:

• Optics and Photonics
• Signal Processing
• Metrology

Background:

• Accurate measurement of temporal waveforms for modulated light is crucial for applications like Frequency-Chirped Continuous-Wave Light Detection and Ranging (FWCW-LIDAR) and serrodyne frequency translation.
• Existing methods may face limitations in precision or applicability to various modulation types.

Purpose of the Study:

• To propose and demonstrate a novel technique for measuring temporal waveforms of phase/frequency-modulated lights.
• To validate the technique's effectiveness for common modulation schemes used in FWCW-LIDAR and serrodyne frequency translation.

Main Methods:

• Utilizing self-heterodyne interferometry with a delay time shorter than the modulation period.
• Employing unwrapped phase detection of heterodyne beat signals via real-time vector signal analysis.
• Leveraging an approximated relationship between beat signal phase and instantaneous frequency.

Main Results:

• Successfully measured temporal waveforms for directly frequency-modulated and externally phase-modulated lights.
• Demonstrated accurate measurement of triangular modulation waveforms with a frequency deviation up to 15 GHz.
• Provided a detailed investigation into deviations between measured and ideal waveforms.

Conclusions:

• The proposed technique offers a robust and accurate method for characterizing modulated light waveforms.
• This advancement has significant implications for the development and optimization of optical systems employing frequency and phase modulation.