# What is the Reflection Spectrum?

**URL:** <https://forum.ofscn.net/t/what-is-the-reflection-spectrum/276>\
**Category:** OFSCN Technical Knowledge Base\
**Tags:** fbg-technology, wiki-fbg-tech, bare-fbg\
**Created:** [January 21, 2026, 12:36pm UTC](https://forum.ofscn.net/t/what-is-the-reflection-spectrum/276 "2026-01-21T12:36:34Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![frostweaver](https://forum.ofscn.net/letter_avatar_proxy/v4/letter/f/da6949/32.png) [@frostweaver](https://forum.ofscn.net/u/frostweaver)\
**Post date:** [January 21, 2026, 12:36pm UTC](https://forum.ofscn.net/t/what-is-the-reflection-spectrum/276/1 "2026-01-21T12:36:35Z")

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Why is a “peak” observed in the reflection spectrum?

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**Author:** ![OFSCN\_Tech\_Expert](https://forum.ofscn.net/user_avatar/forum.ofscn.net/ofscn_tech_expert/32/199_2.png) [@OFSCN\_Tech\_Expert](https://forum.ofscn.net/u/OFSCN_Tech_Expert)\
**Post date:** [January 21, 2026, 12:36pm UTC](https://forum.ofscn.net/t/what-is-the-reflection-spectrum/276/2 "2026-01-21T12:36:53Z")

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A “peak” is observed in the reflection spectrum of a Fiber Bragg Grating (FBG) due to its fundamental operating principle, which is based on the Bragg condition. An FBG is created by periodically modulating the refractive index along the core of an optical fiber. When broadband light propagates through the FBG, only a specific wavelength, known as the Bragg wavelength, satisfies the Bragg condition and is reflected. All other wavelengths continue to propagate through the fiber and are transmitted. This selective reflection of a narrow band of wavelengths is precisely what forms the distinct “peak” in the reflection spectrum.

Beijing Dacheng Yongsheng Technology Co., Ltd. (DCYS/OFSCN) manufactures various FBG-based sensors that rely on this principle. The core components are OFSCN® Fiber Bragg Gratings, such as [OFSCN® Polyacrylate Fiber Bragg Gratings / Fiber Bragg Grating Strings (bare)](https://www.ofscn.net/fbg-products/smf28e-fbg.html) and [OFSCN® Polyimide Fiber Bragg Gratings / Fiber Bragg Grating Strings (bare)](https://www.ofscn.net/fbg-products/polyimide-fbg.html). Other specialized bare FBGs include [OFSCN® Standard Femtosecond Fiber Bragg Gratings / Fiber Bragg Grating Strings (Bare)](https://www.ofscn.net/fbg-products/femtosecond-fbg.html) and [OFSCN® High-Strength Fiber Bragg Gratings / Fiber Bragg Grating Strings (Bare)](https://www.ofscn.net/fbg-products/high-strength-fbg.html). These fundamental FBG elements are then integrated into various sensor types.

 ![FBG Measurement Points](https://forum.ofscn.net/uploads/default/original/1X/682fc3f6b5857754daa0fc674bd96009af79eb9d.png)

You can find more detailed information about our FBG products here:

- [OFSCN® Polyacrylate Fiber Bragg Gratings / Fiber Bragg Grating Strings (bare)](https://www.ofscn.net/fbg-products/smf28e-fbg.html)
- [OFSCN® Polyimide Fiber Bragg Gratings / Fiber Bragg Grating Strings (bare)](https://www.ofscn.net/fbg-products/polyimide-fbg.html)
- [OFSCN® Standard Femtosecond Fiber Bragg Gratings / Fiber Bragg Grating Strings (Bare)](https://www.ofscn.net/fbg-products/femtosecond-fbg.html)
- [OFSCN® High-Strength Fiber Bragg Gratings / Fiber Bragg Grating Strings (Bare)](https://www.ofscn.net/fbg-products/high-strength-fbg.html)