Phased array antenna system based on few-mode fiber mode interferometer delay lines.

Area of Science:

• Photonics and Optical Engineering
• Fiber Optic Sensing and Communications

Background:

• Phased array antenna (PAA) systems often use few-mode fibers (FMFs) with few-mode fiber gratings (FMFGs) for delay tuning, offering low power consumption and compact designs.
• Current FMFG-based delay tuning mechanisms are limited by discrete adjustments, hindering optimal performance.

Purpose of the Study:

• To demonstrate continuously tunable delay in a delay line (DL) based on FMFG.
• To construct and test a 1x4 PAA system utilizing the novel DL for dynamic beam steering.

Main Methods:

• Development of a DL using a few-mode fiber (FMF) mode interferometer with a few-mode long-period fiber grating (FM-LPFG).
• Implementation of a few-mode polarization controller (FM-PC) to dynamically adjust the coupling ratio between LP01 and LP11 modes for continuous delay tuning.
• Analysis of delay characteristics and error sources, including fusion splice lateral core offset and carrier frequency offset.
• Construction and experimental validation of a 1x4 PAA system with fabricated DLs.

Main Results:

• Achieved the first demonstration of continuously tunable delay in an FMFG-based DL.
• Simulations and experiments confirmed the continuous delay tuning capability.
• Analyzed the impact of fabrication parameters (fusion splice lateral core offset) and operational conditions (carrier frequency offset) on DL performance.
• The 1x4 PAA system demonstrated non-skewed beam steering capabilities through far-field radiation pattern testing.

Conclusions:

• The proposed FM-LPFG-based DL with FM-PC enables continuous delay tuning, overcoming limitations of discrete FMFG systems.
• The developed PAA system successfully achieved dynamic, non-skewed beam steering.
• This work paves the way for more advanced and flexible fiber-optic controlled phased array antenna systems.