SWIR-Laser vibrometers

SWIR laser vibrometers operate with invisible infrared light at a wavelength of 1550 nm. They provide a high signal-to-noise ratio and enable reliable measurements on dark, rough, or highly absorbing materials.

Measurement without surface preparation: Reliable acquisition even on dark, matte, or fiber-reinforced surfaces – no retro-reflective tape or reflective sprays required.
Wide measurement range: Frequency bandwidth from DC to 50 MHz and vibration velocities up to 50 m/s.
Eye-safe without protective eyewear: Laser class 1 with an output power below 10 mW – no special safety measures required.
Flexible working distances: From a few millimeters to over 300 m – suitable for microstructures and long-distance measurements.
Long service life: SWIR laser diodes do not require regular replacement – unlike HeNe tubes with limited operating lifetimes.

SWIR stands for Short-Wave Infrared and refers to the short-wave infrared region of the electromagnetic spectrum. Optomet SWIR laser vibrometers operate at a wavelength of 1550 nm – invisible to the human eye, but with physical properties that offer advantages for vibration measurement.

With an output power below 10 mW, the SWIR measurement laser is classified as laser class 1 and is therefore eye-safe. Protective eyewear is not required during normal operation. Since the laser beam is invisible, Optomet systems use a visible green pilot laser (510–530 nm, class 2) for alignment to the measurement point. Alternatively, the SWIR spot can be made visible using an IR detector card.

Technical key data:

Parameter	Value
Measurement laser wavelength	1550 nm (invisible)
Pilot laser wavelength	510–530 nm (green, visible)
Measurement laser class	Class 1, < 10 mW
Pilot laser class	Class 2, < 1 mW

The choice of laser wavelength directly influences measurement quality. SWIR lasers at 1550 nm offer several physical advantages over visible HeNe lasers (632.8 nm), which have practical relevance in real-world applications.

At the same laser class, more laser power is available at 1550 nm than at 632.8 nm. SWIR systems operate with up to 10 mW (class 1), whereas HeNe systems are limited to below 1 mW (class 2). The higher power budget improves the signal-to-noise ratio, especially on weakly reflecting surfaces and over large measurement distances.

SWIR detectors are largely insensitive to thermal emission in the mid-infrared range. Measurements on hot surfaces – such as turbine blades or components in operation – are not affected by thermal radiation.

SWIR laser diodes have a significantly longer service life than HeNe gas lasers. While HeNe tubes need to be replaced after around 10,000 operating hours, SWIR diodes typically operate over the entire lifetime of the device without replacement.

Many technically relevant materials reflect more uniformly in the SWIR range than in the visible spectrum. Dark plastics, matte coatings, or fiber-reinforced composite materials provide a more stable backscattered signal at 1550 nm. This reduces signal dropouts and enables measurements without surface preparation – retro-reflective tape or reflective sprays are not required.

SWIR or HeNe?

SWIR (1550 nm) is the standard choice for most applications – especially for dark surfaces, fiber-reinforced composite materials, and long measurement distances.

→ Optomet SMART Series

HeNe (632.8 nm) is suitable for measurements through water or other liquids, as SWIR radiation is strongly absorbed in these media.

→ Optomet Vector Series (HeNe)

The properties of SWIR lasers – high signal stability, eye safety, and insensitivity to thermal radiation – make them suitable for a range of demanding measurement tasks.

Turbines and high-temperature components

Vibration measurements on components in operation or under thermal load. The SWIR laser is not affected by thermal radiation and provides stable signals even at elevated surface temperatures.

Fiber-reinforced structures (CFRP/GFRP)

In aerospace engineering and lightweight construction, carbon fiber– and glass fiber–reinforced plastics are widely used. SWIR lasers provide a stable backscattered signal on these materials – even without surface preparation.

Biological surfaces

In research, SWIR vibrometers are also used for vibration analysis on biological tissue, where eye safety and gentle, non-contact measurement are particularly important.

Dark and absorbing plastics

In the automotive sector, black or dark plastics are frequently used – for example in dashboards, door panels, or bumpers. These materials reflect visible light only weakly, which can lead to signal loss when using HeNe systems.

Dark and absorbing plastics

For applications such as bridge monitoring, building vibration analysis, or rotor blade measurements, SWIR systems enable working distances of over 300 m. The Nova Xtra achieves measurement distances of up to 300 m.

The SWIR measurement laser at 1550 nm is not visible to the human eye. For alignment to the measurement point, Optomet vibrometers use a green pilot laser (510–530 nm) that runs coaxially with the measurement beam. Alternatively, the SWIR spot can be made visible using an IR detector card.

The SWIR laser is eye-safe: With an output power below 10 mW, it is classified as laser class 1.

Protective eyewear is not required. Infrared radiation at 1550 nm is additionally absorbed by the eye’s aqueous media and does not reach the retina – unlike visible light, which penetrates all the way to the retina.

IR-Detektor Karte macht einen Infrarot Laser sichtbar

Portrait of Tobias Schröder, Head of Sales & Marketing at Optomet

"For more than two decades, Optomet has stood for precise vibration measurement. Our laser vibrometers deliver reliable data – from laboratory analysis to industrial quality control."

Tobias Schröder (M.Sc. Mechanical Engineering)
Head of Sales & Marketing

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Comparison: SWIR vs. HeNe laser vibrometers

Both laser technologies have their justification – the choice depends on the application. The following table compares the key differences.

	SWIR (1550 nm)	HeNe (632.8 nm)
Wavelength	1550 nm (invisible)	632.8 nm (visible, red)
Laser class	Class 1, < 10 mW	Class 2, < 1 mW
Protective eyewear required	No	No
Signal-to-noise ratio	Higher due to greater available laser power	Lower due to limited power
Surface preparation	Generally not required	Depending on the surface, retro-reflective tape or spray required
Measurement through water	No – strong absorption at 1550 nm	Yes – low absorption at 632.8 nm
Measurement on hot surfaces	Yes – insensitive to thermal radiation	Limited – thermal emission can interfere
Long measurement distances	Yes – up to over 300 m	Limited
Laser source lifetime	Long – no regular replacement required	Limited – HeNe tube ages
Spot size (with identical optics)	Larger due to longer wavelength	Smaller due to shorter wavelength
Optomet products	SMART Series, Nova Series, Fiber Series	Vector Series, HeNe scanning vibrometers

Optomet uses SWIR technology as the standard for most vibrometer systems. The products are divided into two series: the modular SMART Series and the CLASSIC Series.

The SMART Series is modular in design and offers systems for a wide range of measurement tasks – from single-point measurements to full-field 3D analysis. All SMART products operate with SWIR lasers (1550 nm).

Learn more about the SMART Series

Product	Description
SMART Single+	Single-point vibrometer for precise measurements at a fixed measurement point
SMART Scan+	Scanning vibrometer for full-field vibration analysis
SMART 3D-Scan	Three synchronized scanners for three-dimensional vibration acquisition
SMART Full Body	Multiple networked scanners for large objects such as vehicles or aircraft structures
SMART DAQ	Data acquisition system for simultaneous measurements at multiple points
SMART Multi-Fiber	Fiber-optic system with multiple sensor heads for parallel measurements
SMART 3D-Fiber	Fiber-optic system for three-dimensional single-point measurement in hard-to-reach locations

The CLASSIC Series comprises standalone vibrometer systems for specific applications. Here as well, SWIR technology is used as standard.

Learn more about the CLASSIC Series

Product	Description
Nova Series	Single-point vibrometer for measurements on dark, rough, or biological surfaces
Nova Xtra	Long-distance vibrometer for measurement distances of over 300 m
Fiber Series	Fiber-optic single-point vibrometer for confined or hard-to-reach measurement locations
Fiber Multiplex	Fiber-optic system with switchable sensor heads for multiple measurement points
Scanning Vibrometer	Scanning system for full-field vibration analysis

In this section, you will find answers to frequently asked questions about SWIR laser vibrometers – including eye safety, wavelength, service life, limitations, and maintenance.

Is a SWIR laser vibrometer eye-safe?

Yes. The SWIR measurement laser operates with an output power below 10 mW and is classified as laser class 1. Protective eyewear is not required during normal operation. Infrared radiation at 1550 nm is absorbed by the eye’s fluids and does not reach the retina.

What wavelength does a SWIR laser vibrometer have?

Optomet SWIR vibrometers operate at a wavelength of 1550 nm in the short-wave infrared range. The measurement laser is invisible; a visible green pilot laser (510–530 nm) is used for alignment.

Does a SWIR laser need to be replaced?

Generally not. SWIR laser diodes have a long service life and typically operate over the entire lifetime of the device without replacement. In contrast, HeNe tubes need to be replaced after approximately 10,000 operating hours.

Are all Optomet vibrometers equipped with SWIR lasers?

Almost all of them. The entire SMART Series as well as most products of the CLASSIC Series (Nova, Fiber, Scanning Vibrometers) operate with SWIR lasers at 1550 nm as standard. The only exception is the Vector Series, which uses a visible HeNe laser (632.8 nm) – suitable for measurements through water or on microstructures with a small spot diameter.

What limitations does a SWIR laser have?

SWIR lasers are not suitable for all applications. The most important limitations:

Measurement through water: SWIR radiation is strongly absorbed by water. For measurements through liquids, a HeNe laser (632.8 nm) is better suited.
Spot size: With identical optics, a SWIR laser produces a larger spot than a HeNe laser – e.g. 89 µm vs. 30 µm at a distance of 500 mm (100 mm optics).

How does the maintenance effort differ between SWIR and HeNe?

SWIR laser diodes do not require regular replacement and involve lower maintenance effort. HeNe gas lasers are subject to natural aging – the tube must be replaced after approximately 10,000 operating hours.

Laser Sources
Fundamentals of the laser types used in vibrometry – Helium-Neon, SWIR, and fiber-coupled systems.

Laser Doppler Vibrometry
Structure, operating principle, and application areas of Laser Doppler Vibrometry.

Vibration Measurement
Methods, measurement setup, and evaluation of vibration data in research and industry.

Doppler Effect
Physical principle of Laser Doppler Vibrometry – the basis for precise velocity measurement.

Signal Processing
Analysis of vibration data using FFT, frequency-domain evaluation, and real-time processing.