# Active Wavelength Control of Fiber Bragg Gratings: A Systematic Review of Tuning Mechanisms, Emerging Applications, and Future Frontiers

## TL;DR

This paper reviews how fiber Bragg gratings can be actively controlled to adjust their wavelength, highlighting new methods and applications in photonics.

## Contribution

A systematic categorization and comparison of active tuning mechanisms for fiber Bragg gratings, along with emerging applications and future research directions.

## Key findings

- Active FBG tuning mechanisms include mechanical, thermal, and electro-optic approaches with distinct performance trade-offs.
- Applications span tunable fiber lasers, microwave photonic systems, and quantum information processing.
- Future advancements depend on novel materials, AI integration, and quantum technologies.

## Abstract

Fiber Bragg gratings (FBGs) have evolved from passive sensing elements into actively programmable photonic components, enabling dynamic wavelength control across diverse applications. This review provides a comprehensive and systematic overview of active wavelength control technologies for FBGs, deliberately excluding passive sensing applications. We systematically categorize the fundamental tuning mechanisms—including mechanical, thermal, optothermal, electro-optic, nonlinear optical, and hybrid approaches—and compare their performance characteristics in terms of tuning range, speed, precision, and trade-offs. Key enhancement techniques, such as mechanical amplification, thermal packaging, femtosecond laser fabrication, and FPGA-based interrogation, are examined. The transformative impact of actively controlled FBGs is elucidated across three major application domains: tunable and narrow-linewidth fiber lasers, reconfigurable microwave photonic systems, and emerging fields including quantum information processing and biomedical imaging. A consolidated technology map visualizes the connections between enabling techniques and applications. Finally, we critically analyze core challenges—performance trade-offs, control complexity, and integration bottlenecks—and outline future research directions driven by novel materials, artificial intelligence, and quantum technologies. This review offers a structured framework for understanding active FBGs as programmable photonic primitives, providing actionable insights for researchers and engineers in academia and industry.