Digitally controlled chirped pulse laser for sub-terahertz-range fiber structure interrogation.

Area of Science:

• Optoelectronics
• Fiber Optic Sensing
• Photonics

Background:

• Accurate real-time monitoring of fiber structures is crucial for various sensing applications.
• Existing methods may lack the required spatial resolution or real-time data acquisition capabilities.
• Sub-terahertz-range fiber structures offer unique properties for advanced sensing.

Purpose of the Study:

• To develop a sweep velocity-locked laser pulse generator for enhanced fiber structure interrogation.
• To demonstrate real-time sensing with millimeter-level spatial resolution.
• To validate the system's capability for distributed strain and temperature sensing.

Main Methods:

• Utilized a digital phase-locked loop (DPLL) circuit to control the sweep velocity of laser pulses.
• Employed a distributed feedback laser with injection current modulation to generate chirped laser pulses.
• Integrated the laser pulse generator with a sub-terahertz-range fiber structure (sub-THz-fs) for sensing experiments.

Main Results:

• Achieved a high-quality linearly chirped laser pulse with a 117.69 GHz frequency excursion.
• Demonstrated real-time interrogation of the sub-THz-fs with millimeter-level spatial resolution.
• Observed a linear response to longitudinal strain and accurately measured a distributed temperature profile.

Conclusions:

• The DPLL-controlled laser pulse generator is effective for real-time, high-resolution sensing of fiber structures.
• The system shows significant potential for distributed strain and temperature monitoring applications.
• This technology advances the capabilities of fiber optic sensing for demanding applications.