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Few-mode fiber true time delay lines for distributed radiofrequency signal processing.
Optics Express
|November 25, 2018
Summary
We demonstrate compact radiofrequency signal processing using true time delay in few-mode fiber. This fiber-distributed processing offers a significant gain in compactness for signal filtering applications.
Area of Science:
- Photonics and Optical Engineering
- Signal Processing
- Fiber Optics
Background:
- Traditional radiofrequency (RF) signal processing often requires bulky and complex hardware.
- True time delay (TTD) is crucial for advanced RF signal processing, enabling functionalities like beamforming and filtering.
- Few-mode fibers (FMFs) offer potential for novel optical signal processing due to their multi-mode propagation characteristics.
Purpose of the Study:
- To report the first implementation of distributed RF signal processing using TTD operation on a step-index few-mode fiber.
- To demonstrate the feasibility of engineering time delays within an FMF link for signal processing.
- To showcase the application of this technology in RF signal filtering and evaluate its compactness.
Main Methods:
- Utilized a 60-meter step-index few-mode fiber supporting 4 LP modes.
- Implemented two configurations with different time delay properties by inscribing long period gratings (LPGs) at specific fiber positions.
- The LPGs converted a portion of the fundamental LP01 mode to the LP02 mode, enabling engineered time delays.
- Experimentally demonstrated the performance of the delay line for RF signal filtering.
Main Results:
- Successfully implemented distributed RF signal processing based on TTD in an FMF.
- Achieved engineered time delays by mode conversion using LPGs within the fiber link.
- Demonstrated RF signal filtering functionality with the developed fiber-distributed processing system.
- Observed a significant gain in compactness, on the order of magnitude, compared to conventional methods.
Conclusions:
- This work presents a novel approach for compact RF signal processing using TTD in FMF.
- Fiber-distributed processing with engineered time delays offers a promising solution for miniaturizing RF systems.
- The demonstrated technique paves the way for more integrated and efficient optical RF signal processing functionalities.
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