FDM – Distance Measuring Systems

Flexible precision

The FDM Series fiber-optic distance measuring systems use high-precision sensors for performing contactless distance, shape and roughness measurements with a resolution in the sub-nanometer range. The specially fabricated miniature fiber-optic probes allow for enormous flexibility. With diameters starting from just 50 µm, they can even access very small or difficult-to-reach cavities. They can be used to scan the holes of injection nozzles or the small gaps between the teeth of precision gear wheels. Standard probes with diameters of 0.8 and 1.3 mm are available for larger cavities.

Thanks to the modular design of the measuring device, the probe and evaluation unit can be placed at almost any distance from each other. High measuring frequencies, integrated interfaces and system-specific software solutions means they can be fully integrated into automated production processes. For inline measurements at production speed.

Product brochure fiber-optic distance measuring systems front page

Product brochure fiber-optic distance measuring systems backside

    Your benefits

  • Measuring in the smallest of spaces (from Ø 0.1 mm)

  • Results with nanometer accuracy

  • Non-contact and wear-free

  • 100-percent inspection capability

  • Almost material and surface-independent

  • Single-point and multi-point measurements possible

  • Generation of 2D profiles and 3D point clouds

  • Standards-compliant quality control according to DIN EN ISO

  • Easy-to-automate and fully integrable

  • Electromagnetic compatibility (EMC)

System characteristics


Highest accuracy

Measuring range80 µm
Accuracy (typical standard deviation)< 3 nm*
Diameter of the measuring probe≥ 50 µm

*For point mea­sure­ment at a working distance of 0.1 mm on polished glass.


Large measuring range

Measuring range1 mm
Accuracy (typical standard deviation)< 10 nm*
Diameter of the measuring probe≥ 50 µm

*For point measurement at a working distance of 0.1 mm on polished glass.

General parameters

Fiber-optic distance measuring system FDM-1 by fionec Fiber-optic distance measuring system FDM-1 rear view featuring interfaces Fiber-optic distance measuring system FDM-2 front view

Mea­sure­ment principle

low coherence interferometry

Probe diameter

0.05 / 0.08 / 0.125 / 0.8 / 1.3 – 5 mm

Measurable materials and surfaces

Glas, metal, ceramics, plastic etc. – trans­parent, glossy, matt

Inner diameter of the tested object

from 0.1 mm

Direction of measure­ment

axial (0°), angular (45° – 90°)

Measuring frequency

up to 20 kHz (depending on the surface)

Multi-point measure­ment

paral­lel or sequen­tial read-out from multiple probes


FDM­Control (control software) / Data­Viewer (analysis software)

Pro­gram­ming inter­faces


System inter­faces (configurable)

Trigger IN, Gate IN, Trigger OUT: TTL 5V, Ethernet, GPIO

Power supply

230 V (AC)


The FDM sensor is particularly suited for applications in the precision and ultra-precision manufacturing sector. The miniaturized probes allow for flexible, contactless and highly precise inspections of difficult-to-access surface structures and cavities.

Characterization of surfaces

  • Detecting the roughness and waviness of technical surfaces
  • Monitoring and determining tool wear
  • Inspecting optics, wafers and optical flats
  • Measuring in scan mode for 2D/3D representation of free-form surfaces such as the flanks of gear wheels

High-accuracy distance measurement

  • Measuring expansion, drift, wear and vibrations on ultra-precision machines and machine tools
  • Highly accurate position detection for component alignment and tool position determination multi-point measurement possible

Testing form and position (GD&T)

  • e.g. roundness, flatness, straightness, parallelism, circular run-out

Measuring in tiny and hard-to-access spaces

  • e.g. micro-drilled holes, holes of injection nozzles, gaps between the teeth of precision gear wheels

Integration in precision coor­dinate mea­suring machines, auto­matic testing apparatus or UP-machine tools

  • Compatibility and automation thanks to serial interfaces
  • Single or multi-point measurements
  • Inline measurements at production speed
  • Industry 4.0 applications

We’ll be happy to develop customized solutions for your specific measurement task.