Researchers at Shenzhen University have experimentally demonstrated a new approach for filtering broadband optical signals using chirped and tilted fiber Bragg gratings (CTFBGs). The study, published in the Journal of Lightwave Technology, shows that this technique offers highly flexible, customizable, and efficient wavelength filtering that surpasses the limitations of conventional fiber Bragg grating designs.
Unlike uniform or chirped FBGs, which struggle to handle large optical bandwidths, the CTFBG method enables band-rejection filtering with more than 100 nm of bandwidth. The team reported low insertion loss, high slope efficiency, negligible back-reflection, and strong resilience to environmental changes such as temperature fluctuations, axial strain, and bending. This makes the CTFBG approach suitable for demanding optical applications in communications and sensing.
The researchers fabricated the gratings using femtosecond laser line-by-line (LBL) technology, which allows precise control over spectral characteristics. Potential applications include high-quality band-rejection filters, edge filters, and gain equalizers for optical communication systems and advanced photonic networks.
• CTFBG enables broadband filtering with more than 100 nm bandwidth
• Demonstrated high filtering slope efficiency and broadband tunability
• Insensitive to temperature, axial strain, and bending
• Fabricated using femtosecond laser line-by-line technology for improved spectral control
• Suitable for band-rejection filtering, edge filters, and gain equalizers
“The CTFBGs have the advantages of large filtering bandwidth, high filtering slope efficiency and exceptional broadband tunability, which makes them increasingly used in high-quality band-rejection filtering, edge filtering, and gain equalizers,” said Dr. Fan of Shenzhen University.
🌐 Analysis: The ability to achieve tunable, broadband filtering without significant signal degradation would be beneficial for high-capacity optical transport and data center interconnects. Similar advances in femtosecond laser fabrication are being pursued globally, with CTFBGs positioning themselves as a key component in photonic integration strategies for 400G and beyond.