Photonic generation of frequency-tunable biphase and quadriphase coded pulse signals without background interference...

Area of Science:

• Photonics and Optical Engineering
• Signal Processing
• Modulation Techniques

Background:

• Traditional phase-coded pulse generation methods often face limitations such as background interference and power dependency.
• Achieving frequency tunability and flexible coding (biphase/quadriphase) in optical signal generation presents significant challenges.

Purpose of the Study:

• To propose and demonstrate a novel approach for generating frequency-tunable biphase and quadriphase coded pulse signals.
• To overcome limitations of existing methods by eliminating background interference and power dependency.
• To achieve flexible switching between biphase and quadriphase coding schemes.

Main Methods:

• Utilizing a polarization division multiplexing dual-parallel Mach-Zehnder modulator (PDM-DPMZM).
• Employing a polyphase encoder based on vector modulation to map ternary code sequences to orthogonal optical carriers.
• Controlling bias voltage for frequency tunability (fundamental or doubled frequency).
• Adjusting polarity of ternary code sequences to achieve four phase shifts.

Main Results:

• Successful generation of frequency-tunable phase-coded pulse signals at 12 and 24 GHz.
• Demonstrated ability to switch between biphase and quadriphase coding.
• Experimental validation using Barker and Frank codes confirmed good performance in terms of peak-to-sidelobe ratio (PSR), range-Doppler coupling, and Doppler tolerance.
• Overcame power-dependent limitations of previous techniques.

Conclusions:

• The proposed PDM-DPMZM based approach offers a robust and flexible method for generating advanced phase-coded pulse signals.
• This technique provides significant advantages for applications requiring tunable frequencies and adaptable coding schemes, such as in radar and optical communications.
• The method effectively addresses background interference and power limitations, paving the way for improved system performance.