# What is a "fusion splicer"?

**URL:** <https://forum.ofscn.net/t/what-is-a-fusion-splicer/2861>\
**Category:** OFSCN Technical Knowledge Base\
**Tags:** fbg-technology\
**Created:** [September 17, 2026, 4:03am UTC](https://forum.ofscn.net/t/what-is-a-fusion-splicer/2861 "2026-09-17T04:03:57Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![VoidWalker](https://forum.ofscn.net/letter_avatar_proxy/v4/letter/v/848f3c/32.png) [@VoidWalker](https://forum.ofscn.net/u/VoidWalker)\
**Post date:** [September 17, 2026, 4:03am UTC](https://forum.ofscn.net/t/what-is-a-fusion-splicer/2861/1 "2026-09-17T04:03:57Z")

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How does that box, which looks like a small computer, automatically align the two cores, which are thinner than a hair?

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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:** [September 17, 2026, 4:04am UTC](https://forum.ofscn.net/t/what-is-a-fusion-splicer/2861/2 "2026-09-17T04:04:13Z")

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A fiber optic fusion splicer’s ability to precisely align and fuse single-mode fiber cores, which are only about 9\ \mu\text{m} in diameter (roughly one-tenth the diameter of a human hair), with sub-micron accuracy (\< 0.5\ \mu\text{m}) primarily relies on the synergistic coordination of the **optical lens imaging principle** , **digital image processing** , **high-precision nano-movement mechanisms** , and **physical melting characteristics**.

Its complete automated core working principle can be divided into the following four steps:

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### 1. Core Imaging Principle: Profile Alignment System (PAS)

Single-mode fibers have a cladding diameter of 125\ \mu\text{m}, with the central light-guiding core measuring only about 9\ \mu\text{m} in diameter. Ordinary microscopes cannot directly penetrate the cladding to see the internal core. The fusion splicer utilizes the fiber’s inherent physical refractive properties:

- **Cylindrical Lens Effect** : A collimated LED light source illuminates the fiber from the side. Because the fiber is a cylindrical piece of transparent glass, it naturally acts as a “cylindrical lens.”
- **Refractive Index Difference** : The core is typically doped with a small amount of germanium dioxide ( \text{GeO}\_2 ), which has a slightly higher refractive index (n\_{\text{core}} \approx 1.468) than the pure silica cladding (n\_{\text{cladding}} \approx 1.462).
- **Characteristic Light Intensity Distribution** : As light passes through the fiber, it refracts and focuses, creating a unique brightness distribution curve on the CMOS/CCD image sensor at the back. By analyzing the intensity valleys and peaks, image processing algorithms can accurately locate the core axis positions of the two fibers at an algorithmic level.

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### 2. Orthogonal Bidirectional 3D Perception (X / Y Axis Observation)

To achieve absolute alignment in three-dimensional space, the fusion splicer is equipped with two sets of high-magnification optical microscope objectives oriented at 90^\circ to each other:

- They simultaneously capture side-projected images of the fibers from both the **X-axis** and **Y-axis** perspectives.
- The image processor analyzes the images from both axes in real-time to calculate the horizontal deviation (\Delta X), vertical deviation (\Delta Y), end-face gap (\Delta Z) between the left and right fibers in space, as well as their end-face cleave angles. If the cleave angle is too large or there are burrs, the algorithm will automatically issue an error and stop.

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### 3. Micron / Nanometer-Scale Mechanical Alignment Platform

After identifying the spatial deviations, the internal mainboard controller drives precision mechanical actuators:

- The fibers are held in precision **V-groove** clamps.
- The base is driven by high-precision stepper motors coupled with precision ball screws or **piezoelectric actuators (PZT)**.
- Based on visual feedback, the control system makes sub-micron adjustments (stepping accuracy can reach tens of nanometers) to the V-groove positions on both sides until the fiber core axes in both the X and Y planes are perfectly coincident.

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### 4. Arc Discharge and Surface Tension Self-Alignment

Upon completion of alignment, the machine performs two stages of high-voltage arc discharge:

1. **Pre-discharge (Cleaning Arc)**: A weak, short arc is discharged to remove micro-dust and static electricity adhering to the fiber end faces.
2. **Main Splicing Discharge (Main Arc)**: Two tungsten electrodes generate a high-voltage plasma arc of several thousand volts, creating an instantaneous high temperature of approximately 1600^\circ\text{C} \sim 2000^\circ\text{C} at the fiber joint. This softens and melts the quartz glass.
3. **Advancement and Self-Alignment** : During the moment of fusion, precision motors push the two fibers a small distance further along the axis (Overlap/Push). Simultaneously, the liquid quartz glass, under the influence of extremely high **surface tension** , undergoes a self-centering effect (Self-centering Effect), further eliminating minor axial misalignments and ultimately fusing into a continuous fiber segment.

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_Note: Fiber optic fusion splicers are general-purpose tools for fiber optic communication construction and device fabrication, and do not belong to the core product series of Beijing Dacheng Yongsheng Technology Co., Ltd. (OFSCN®). Beijing Dacheng Yongsheng Technology Co., Ltd. focuses primarily on the research, development, and production of fiber Bragg grating sensing elements, high-temperature resistant special optical fibers, and armored fiber packaging technology._