Measure refractive index of optical fibers up to 600 µm in seconds!
The nPA-600 is the quick, easy and low-cost way to get the refractive index data you need to verify your standard and specialty fibers.
Minimum fiber preparation is required, and the clean, efficient graphical user interface allows the user to fully characterise their fibers, with minimal training or experience. The nPA-600 provides accurate and repeatable refractive index data, giving valuable information about fiber design and the manufacturing process. The nPA-600 comes with nPA v2.1 software which boosts system performance and improves user experience, and its new API allows the nPA-600 to integrate to other systems seamlessly.
The nPA-600 Refractive Index Profiler uses a modified refracted nearfield technique to analyse the end-view grey-scale intensity profile of a fiber to determine its full 2D refractive index distribution.
There is no need to rotate the fiber or scan the fiber endface, resulting in a very fast measurement, meaning that the nPA-600 is suitable for production lines, research and development labs, or QA environments.

Features and Benefits
- Measure fibers up to 600 µm in diameter
- Prepare and measure a fiber sample in under 2 minutes (2D measurement in seconds)
- Measures circularly symmetric fibers and non-circularly symmetric fibers, such as polarisation maintaining, octagonal, and multi-core fibers
- Preinstalled with production-ready nPA v2.1 software
- Region cursor markers give an average of the refractive index of the marked region
- Option to display target refractive index template alongside with actual fiber profile
- API facilitates users customisation and integration with other systems.
- Various measurement and output options for better system performance and user experience
- Traceable calibration and new calibration tools
nPA-600 Refractive Index Profiler

Graded index multimode fiber | ![]() | ![]() |
PANDA PM fiber | ![]() | ![]() |
PM fiber with elliptical stress rods | ![]() | ![]() |
7-core multicore fiber | ![]() | ![]() |
Octagonal active fiber with pedestal surrounding the core | ![]() | ![]() |
Calibration fiber | ![]() | ![]() |
The latest release nPA v2.1 software improves user experience and boost system performance.
Feature | Benefit |
---|---|
Target refractive index template alongside the actual fiber profile | Enable users to view the fibers refractive index against the target profile. |
More viewing and output options | Improve user experience and enable easy reporting and documentation for production |
“Region Cursors” measurement | Obtain an average of the refractive index of the marked region |
“Flag” colour palette | Highlight the minute changes in refractive index |
New API | Enables users customisation and integration with other systems |
New calibration tools | Enables measurement accuracy over time |
Screenshots

The nPA-600 with nPA v2.0 software measures fibers (including octagonal fiber) up to 600 μm in diameter with customised measurement points and regions.

Repeatability* | |
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Refractive Index Repeatability | 0.0002 |
Measurement Capability | |
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Fiber Diameter | up to 600 µm |
Fiber Material | Silica glass |
Measurement Time** | < 10 seconds |
Measurement Range*** | +/- 0.025 |
Optical | |
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Measurement Wavelength | 630 nm |
Field of View | 830 µm |
Image Sensor | APS-C CMOS, 6480 x 4860 pixels resolution |
Dynamic Range | 73 dB |
Physical | |
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Weight | 6 kg |
Size | 0.5 x 0.16 x 0.13 m |
Operating Temp | 15 – 30° C |
Performance Specification | Validated at 22° C |
Computer Requirements | All systems are supplied with a computer running up-to-date Windows operating system. |
Data Interface | 1 X USB 3.1 (USB A to USB B: 1m cable supplied) |
* measured on a 125 µm MM fibre sample without removing from the measurement cell
** averaging 5 images
*** around reference fluid index
Part number | Description |
---|---|
nPA-600 | Optical Fiber Refractive Index Profiler for full 2D measurement of optical fibers with diameters between 40 µm and 600 µm. Including optical unit, nPA-IL-1.4680 refractive index liquid kit, nPA-CS100 set of cover slips, nPA-FTK-600 fiber test kit, nPA-CC rigid carrying case, nPA-F0270 and nPA-F0620 ferrule pins, cables, software package, APL-DC desktop computer, keyboard and mouse. |
Ferrule Pins | |
nPA-F0125 | nPA-600 Fiber guide assembly for optical fiber with outer diameter of up to 125 µm |
nPA-F0230 | nPA-600 Fiber guide assembly for optical fiber with outer diameter of 125 – 230 µm |
nPA-F0270 | nPA-600 Fiber guide assembly for optical fiber with outer diameter of 230 – 270 µm |
nPA-F0440 | nPA-600 Fiber guide assembly for optical fiber with outer diameter of 270 – 440 µm |
nPA-F0520 | nPA-600 Fiber guide assembly for optical fiber with outer diameter of 440 – 520 µm |
nPA-F0570 | nPA-600 Fiber guide assembly for optical fiber with outer diameter of 520 – 570 µm |
nPA-F0620 | nPA-600 Fiber guide assembly for optical fiber with outer diameter of 570 – 620 µm |
Optional Accessories | |
nPA-IL-1.4680 | Bottle of Immersion liquid, 10 ml, ( Refractive Index = 1.4680, measured at 589 nm and 25°C ) for refilling nPA measurement cell assembly, including syringes and nozzles |
nPA-SOC | Replacement oil cell for nPA-600 |
nPA-CS100 | Set of 100 replacement cover slips for use with nPA-600 oil cell |
nPA-CC | nPA-600 rigid carrying case |
nPA-600EW3 | nPA-600 Refractive Index Profiler extended warranty covering parts and labour for 3 years from purchase, return to base. Cover excludes camera |
nPA-600EW5 | nPA-600 Refractive Index Profiler extended warranty covering parts and labour for 5 years from purchase, return to base. Cover excludes camera |