Intermodal Four-Wave Mixing Process in Strain-Induced Birefringent Multimode Optical Fibers

Area of Science:

• Nonlinear Optics
• Optical Fiber Communications
• Condensed Matter Physics

Background:

• Intermodal four-wave mixing (IM-FWM) is a key nonlinear process in multimode optical fibers.
• Strain-induced birefringence in optical fibers can alter light propagation characteristics.
• Understanding IM-FWM in birefringent fibers is crucial for advanced optical signal processing.

Purpose of the Study:

• To investigate the partially degenerate IM-FWM process in nonlinear multimode optical fibers with strain-induced birefringence.
• To analyze the dependence of nonlinear frequency conversion and output modal field profiles on the degree of birefringence.
• To determine the optimal pump beam polarization for efficient IM-FWM.

Main Methods:

• Experimental investigation of IM-FWM in optical fibers subjected to uniform diameter stress.
• Analysis of the photoelastic effect causing birefringence due to fiber winding.
• Characterization of nonlinear frequency conversion efficiency and modal field profiles for varying birefringence.
• Evaluation of IM-FWM efficiency with different pump beam polarizations (532 nm sub-nanosecond pulses).

Main Results:

• Birefringence significantly affects the order of excited moduli in different fiber sections.
• Nonlinear frequency conversion and modal field profiles are dependent on the degree of birefringence.
• Over 30% conversion efficiency was achieved for fiber lengths of tens of centimeters.
• Specific pump beam polarizations were identified as most effective for the IM-FWM process.

Conclusions:

• Strain-induced birefringence in multimode optical fibers plays a critical role in modulating IM-FWM.
• The study demonstrates a high conversion efficiency for IM-FWM in short fiber lengths under specific conditions.
• Findings provide valuable insights for designing and optimizing nonlinear optical devices utilizing IM-FWM.