# Spatial Resolution of FBG Systems

**URL:** <https://forum.ofscn.net/t/spatial-resolution-of-fbg-systems/257>\
**Category:** OFSCN Technical Knowledge Base\
**Tags:** fbg-technology, wiki-fbg-tech, fbg-strain-sensor, fbg-displacement\
**Created:** [January 20, 2026, 12:45pm UTC](https://forum.ofscn.net/t/spatial-resolution-of-fbg-systems/257 "2026-01-20T12:45:20Z")\
**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 20, 2026, 12:45pm UTC](https://forum.ofscn.net/t/spatial-resolution-of-fbg-systems/257/1 "2026-01-20T12:45:20Z")

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In quasi-distributed sensing, what limits the minimum distance between two adjacent gratings？

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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 20, 2026, 12:45pm UTC](https://forum.ofscn.net/t/spatial-resolution-of-fbg-systems/257/2 "2026-01-20T12:45:30Z")

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In quasi-distributed fiber Bragg grating (FBG) sensing systems, the minimum distance between two adjacent FBG sensors is primarily limited by **spectral separation** and the **physical length of the grating**.

1. **Spectral Separation:** Each FBG reflects a specific Bragg wavelength. To ensure that an optical interrogator can uniquely identify and track each FBG, their Bragg wavelengths must be sufficiently separated in the optical spectrum. This separation must account for:

2. **Physical Grating Length:** While spectral separation is often the dominant factor for the _sensing_ distance, the FBGs themselves have a physical length (typically a few millimeters to several centimeters). Physically, two FBGs cannot be placed closer than their individual lengths, plus any necessary lead-in/lead-out fiber and packaging.

For applications requiring compact, closely spaced strain measurements, OFSCN provides solutions like the [OFSCN® Polymer-encapsulated Fiber Bragg Grating Strain Sensor (0.7mm/1.2mm diameter)](https://www.ofscn.net/fbg-products/strain-sensor-4.html). These sensors are designed with small diameters to facilitate integration in tight spaces.

Here is an example of an FBG strain sensor:

 ![OFSCN Polymer-encapsulated Fiber Bragg Grating Strain Sensor](https://forum.ofscn.net/uploads/default/original/1X/fe168a6b2156b0e406e1a3a769a1ffba00a450df.jpeg)