Ultralinear 140-GHz FMCW signal generation with optical parametric wideband frequency modulation enabling 1-mm range...

Area of Science:

• Optoelectronics
• Nonlinear Optics
• Signal Processing

Background:

• Conventional frequency-modulated continuous-wave (FMCW) signal generation is limited by electrical modulator bandwidths.
• Optical parametric wideband frequency modulation (OPWBFM) offers potential for wider bandwidths but can suffer from phase noise expansion.
• Phase noise synchronization is critical for maintaining signal quality in OPWBFM.

Purpose of the Study:

• To demonstrate ultralinear and ultrawideband FMCW signal generation using the OPWBFM method.
• To address and mitigate phase noise expansion issues in the OPWBFM process.
• To achieve high-resolution distance measurements using the generated FMCW signals.

Main Methods:

• Utilized a cascaded four-wave mixing (FWM) process for optical bandwidth expansion.
• Employed an optical frequency comb to synchronize the phase of the input conjugate pair.
• Generated a 140-GHz FMCW signal for experimental validation.

Main Results:

• Successfully generated an ultralinear 140-GHz FMCW signal with expanded bandwidth beyond electrical modulator limits.
• Mitigated phase noise expansion by using a frequency comb in conjugate pair generation.
• Achieved a range resolution of approximately 1 mm in fiber-based distance measurement.

Conclusions:

• The OPWBFM method enables ultralinear and ultrawideband FMCW signal generation.
• Phase synchronization using an optical frequency comb effectively reduces phase noise expansion.
• This approach demonstrates the feasibility of high-resolution, short-measurement-time FMCW systems.