Performance evaluation of selective mode conversion based on phase plates for a 10-mode fiber

Area of Science:

• Optical Engineering
• Photonics
• Fiber Optics

Background:

• Higher-order mode conversion is crucial for advanced fiber optic communication systems.
• Phase plates offer a potential method for generating specific linearly polarized (LP) modes in few-mode fibers (FMFs).

Purpose of the Study:

• To numerically and experimentally evaluate the performance of phase plates for higher-order mode conversion in 10-mode fibers (10MFs).
• To investigate the impact of fabrication errors on mode conversion efficiency and beam quality.
• To determine the suitability of phase plates for converting to different LP modes in 10MFs.

Main Methods:

• Numerical simulations were performed to analyze the effects of phase-difference errors and phase jump slopes.
• Coupling power efficiencies and crosstalk were calculated for various LP mode excitations.
• Experimental validation was conducted for mode conversion to LP21 and LP31 modes using fabricated phase plates.

Main Results:

• Fabrication errors like phase-difference error (±2%) and slope width (<0.05) significantly affect the spatial pattern symmetry of converted beams.
• High accuracy in input beam waist adjustment is needed (< -20 dB crosstalk) for LP mode excitation.
• Phase plates are effective for LP02, LP21, and LP31 mode conversion, but not for LP11 and LP12 due to unavoidable crosstalk.
• Experimental results demonstrated high-quality LP21 and LP31 mode generation with minimal crosstalk.

Conclusions:

• Phase plates are a viable technology for specific higher-order mode generation (LP02, LP21, LP31) in 10MFs.
• Careful control of fabrication errors and input beam parameters is essential for optimal performance.
• The study provides guidelines for designing and implementing phase plate-based mode converters for fiber optic applications.