The FT-NIR: fibered NIR spectrometer with a spectral range from 900 to 2500 nm

If you are looking for a high performance, compact and affordable NIR spectrometer, the ARCoptix FT-NIR Rocket is the instrument that you need. Thanks to its permanently aligned interferometer and solid-state reference laser, the FT-NIR Rocket offers excellent stability in both intensity and wavelength scales. The FT-NIR Rocket is compatible with light sources and sampling accessories (like fibers, cuvette folder, ...) typically used with array-detector based NIR spectrometers.


The FT-NIR Rocket is a high-performance system combining high resolution, broad wavelength range and excellent sensitivity. The FT-NIR functioning principle permits to measure over a much broader range than grating spectrometers that are limited to 2100nm. Its outstanding stability in both wavelength and intensity scales makes it an ideal tool for highly reproducible chemometric analysis.In comparison to array-photodiode NIR spectrometers, the single photodiode operation of the FT-NIR ensures no defect pixels, no gain variation among pixels and no dark-current drifts. Also, the device does not suffer from stray-light as grating spectrometers.

Example of application using the ARCoptix FT-NIR spectrometer with the ARCoptix ARCSPHERE (diffuse reflection accessory)


  • Wide wavelength range 0.9-2.5μm
  • High resolution 2cm-1
    (equivalent to <0.25nm@1um and <1.25nm@2.5um)
  • Excellent stability in intensity & wavelength scale (no dark current-induced drift, internal reference laser)
    • Very good sensitivity (2TE cooled InGaAs)
  • Compact and rugger, easy-to-use fiber input system
  • Cost effective (single NIR photodiode)
How does it work?
Permanentely aligned interferometer

The heart of the FT-Rocket is dual corner-cube (retro-reflector) interferometer. The two corner-cubes are fixed to a common swinging arm, which rotates to create an optical path difference (with respect to the beam splitter) in the two arms of the interferometer.
This type of design is called a permanently aligned interferometer. This particular arrangement of the interfeormeter is known to be the most robust against vibrations and temperature drifts. It never has to be realigned.
The swinging arm of the interferometer rotates on wear-free flexure system, making this mechanical system extremely robust and durable.

Solid-state reference laser

For measuring the movement of the mirrors, a solid-state reference laser is coupled into the interferometer. Compared to classic HeNe lasers, the solid-state lasers that we use are more compact and have a much longer life-time. They have a very low temperature-induced wavelegnth drift and, when kept at constant temperature with a Peltier element, their wavelength can be stabilized to a few PPM, thus providing a very accurate and reproducible wavelength scale. This is crucial for ensuring a day-to-day and unit-to-unit consistency..

Model FTNIR-L1-025-2TE
Type of interferometer Permanentely aligned, double retro-reflector design
Spectral range [cm-1]

4000 - 11000

Spectral range [nm]

900 - 2500

Spectral resolution in wavenumber: 2cm-1, 4cm-1, 8cm-1 (user selectable)
(4cm-1 resolution, 1 minute scan time)
Long term baseline intensity stability < 2% (1100-2500nm) over 10 hours
Wave-number repetability < 10ppm
Detector Extended type InGaAs PIN photodiode, 2TE cooled
Scan frequency >4 Hz @ 4cm-1
Optical fiber connector SMA 905
Optical entrance

< 0.6mm (fiber core diameter)

Reference laser Solid-state 795nm, temperature stabilized.
A/D converter 24 bit
Power requirements

10W (max) @12 VDC

Operating temperature 5°C-40°C
Communication interface USB 2.0
Software interface Windows 7, 10 & 11
API for controlling the instrument via our DLL
Dimensions 180mm x 160mm x 80mm
Weight 1700g


Frequently Asked Questions
What is the resolution of the FT-NIR Rocket in nm (wavelengths)?

The resolution of Fourier-transform spectrometers is usually expressed in wave-numbers (ν), which are simply the inverse of wavelength (ν=1/λ). The conversion betwen wave-number resolution and wavelength resolution is Δλ = λ2 · Δν. The the graph below shows this conversion for the situations where Δν = 2cm-1, 4cm-1 or 8cm-1.

Can I use the FT-NIR Rocket with standard fiber-optics accessories?
Yes. Although the ARCoptix FT-NIR is not a dispersive but a Fourier-transform spectrometer, accessories normally used with dispersive spectrometer are compatible. The spectrometer has a SMA-905 input fiber connector. One just has to take care that accessories are NIR compatible. For example, optical fibers must be rated "low-OH content" to avoid too high absorption in the NIR.
What is the temperature-stabilized internal reference laser?
The precision of the wavelength scale in Fourier-transform spectrometers relies on its internal reference laser. In our compact FT spectrometers, the reference laser is a solid-state type whose central wavelength has a naturally low temperature-induced drift, ~70 ppm/ºC. In some applications, this is sufficient. But in other applications, a more reproducible wavelength scale must be achieved by the spectrometer. With the temperature-stabilization of the laser (via a thermoelectric element) a wavelength reproducibility < 10 ppm can be guaranteed all over the instrument operational temperature range (5-40 ºC). To give an example, at 1000nm wavelength, a shift of 10 ppm means 10E-6 * 1000nm = 0.01nm. This is especially important for applications such as laser characterization or chemometric analysis.
ARCoptix Digital Acquisition Acquisition system: AoDAQ

The AoDAQ is a multi-threading, cross-platform and versatile software that simultaneously takes care of:

  • (1) Handling communication with the FT-IR via USB
  • (2) Processing raw signals to deliver the spectrum
  • (3) Running a TCP ethernet server

The AoDAQ can be installed on all sorts of computers, from desktop machines to embedded, low-power single board computers. Thanks to the hosting of a TCP server, the instrument data and parameters can be accessed locally and/or remotely. All communication with the instrument eventually reduces to a set of TCP/IP commands that allow to quickly acquire data, adjust parameters, monitor the instrument status etc. using the programming environment of your choice.

Free GUI basic software

The FTIR Rocket is delivered with a free Windows 7 & Windows 10 compatible graphical user interface (GUI) program.

The free basic software package allows the user to:

  • Configure hardware measurement parameters (amplifier gain, averaging, ...).
  • Display real-time spectral measurement results.
  • Set reference spectra (white, dark) and choose among raw spectra, transmission or reflection mode.
  • Perform usual operations such as save, open, zoom, rescale...
  • Select features specific to Fourier transform spectrometry: choose among spectrum or interferogram averaging, apodization, look and save the interferograms, etc.
Free API & Examples

The FTIR Rocket is also delivered with a free API that allows you to control the spectrometer with custom code via our DLLs. Examples are available for the following languages:

  • C++
  • C#
  • Labview
  • Matlab
Advanced data processing & analysis software
In collaboration with Labcognition GmbH in Germany we also offer additional Panorama software packages:
Math Add-on module

contains a set of standard manipulation operations used in spectroscopy, like normalization, derivative, baseline correction, peak picking and more. In addition some special operations are available, like multiplicative scatter correction, thickness correction or standard normal variate correction and others.

Quantity Add-on module
is an expert in multivariate data analysis with quantitative methods like PLS and MLR. A convenient and intuitive wizard guides you through all steps of calibration model development. Complex statistical methods become very easy to use even for non-experienced users.
Search Add-on module
is an ideal add-on to archive your spectroscopic data and related information. It includes spectrum and full text search functionality on spectral libraries of various different library formats or directly on data in the file system.
IRAnalyze software package

is a highly sophisticated IR spectrum interpretation tool. Based on an IR spectrum, it provides you with automatic results for IR bands to functional group correlations and their characteristic frequencies. Furthermore, it is a comprehensive electronic dictionary to browse frequiencies for correlated IR bands.


Transmission measurement

The sketch below shows a typical configuration for using the FT-NIR Rocket for transmission measurements. In addition to the spectrometer, you will need one NIR light source, a cuvette/sample holder and 2 NIR optical fibers.

ArcLight NIR lamps

The ARCoptix ArcLight NIR is the version of our lamp optimized for the VIS-NIR (400 – 4,000nm) spectral range. It uses a high temperature (>2850 K), 20W QTH bulb. The lamp has a removable fiber coupler SMA-905 connector that allows switching between free-space and fibered optics.

DOWNLOAD Datasheet of ArcLight Lamps


Cuvette / sample holder (CUV-NIR)

The CUV-NIR is a cuvette holder ideal for the visible to near-infrared (0.4-2.6 microns). It comes with 2 fiber collimators / fiber couplers with SMA-905 connectors. The sample slot is 12.5mm wide, thus accepting glass cuvettes with an optical path of up to 10mm. The CUV-NIR has an additional slot to hold a filter, e.g to reduce heating of the sample and shot noise due to light out of the spectral range of interest.



Diffuse reflection measurement

Another typical measurement configuration is diffuse reflectance. There are several possible configurations, among which a very good one is to use our internally illuminated integrating sphere, as shown in the video below.

Integrating sphere with internal light source (ArcSphere-50-Hal)

The ArcSphere-50-Hal is an integrating sphere with internal halogen light source for diffuse reflection VIS/NIR measurements. The ArcSphere-50-Hal has an internal
diameter of 50mm, a sample port diameter of 10mm, and an SMA-905 fiber connector to connect to the spectrometer.
The internally illuminated integrating sphere provides a much stronger signal than spheres illuminated via fiber optic coupled.


DOWNLOAD Datasheet ArcSphere-50-Hal


Non-exclusive Distributor list for spectrometers:
For OEM Business: contact Arcoptix directly. FTIR OEM Business
France, Germany
Italy, UK

Russia, Moscow FTIR Russia

South Korea
Switzerland and
Rest of the world
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