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Vacuum Technology

From the vacuum screw to the complete vacuum chamber.

Optical Fiber Feedthroughs

Optical fibers are used in a vacuum for metrological tasks when the point of application or origin of the light is difficult to reach. They allow great flexibility with regard to the guidance of the light beam. Depending on the application and type of fibre, however, these effects can be reduced or completely suppressed. VACOM uses standard fibers for optical fiber feedthroughs to ensure a high degree of user-friendliness and compatibility. However, a wide variety of special fibers can of course also be installed according to customer specifications.

Properties of optical fiber feedthroughs

Optical fiber feedthroughs (OFDs for short) for vacuum applications combine the properties of two different engineering disciplines. On the one hand, the vacuum-related properties must meet those of the typical vacuum standard, which include the choice of material, the operating temperature, the outgassing behaviour and the He leakage rate.
On the other hand, the optical requirements must be met. These mainly lie in very good insertion loss and high return loss. In addition, adaptability to a common connector system, such as FC/APC & FC/PC or FSMA, must of course be guaranteed.

Application areas

The application areas of fibre feedthroughs cover a wide spectrum. They are used, for example, in interferometric position measurement technology, where single-mode fibres are used, and in confocal chromatic measurement technology with small-core multimode fibres. In addition, applications for spectroscopic problems can also be realised. Prominent representatives are plasma and white light spectroscopy with large-core multimode fibres.
VACOM's product range extends from optical fibre feedthroughs with various standard single-mode and multimode fibres to atmospheric cables and customised vacuum cable assemblies.

On request, we also offer focused solutions with non-standard fibres. Our customer advisors will be happy to help you at this point.

Already developed non-standard solutions:

  • Collimation optics for vacuum applications
  • Feedthrough of a fibre bundle
  • Fabrication of metal-coated vacuum fibres
  • Guiding of fibres in stainless steel protection tubes

An experienced team of optics specialists, material scientists and vacuum technicians is looking forward to finding a suitable solution for your special application. 

The OFDs manufactured by VACOM with integrated single-mode fibre are designed for the wavelength specified in each case. They can be used in a relatively small wavelength range around the corresponding operating wavelength. Due to the small fibre core diameter of single-mode fibres, only the propagation of one mode is possible for geometric reasons. Below the respective specified cut-off wavelength, the fibre begins to develop multimode properties. Since single-mode fibres are often operated with laser sources, the use of FC/APC connectors is recommended. This breaks back reflections at the coupling points into the fibre cladding and at the same time optimises the signal to noise ratio. VACOM's fabricated optical fibre feedthroughs have excellent vacuum characteristics combined with outstanding optical properties. These include low outgassing, low He leakage rate and low insertion loss (high transmission). Therefore, our OFD is used for a variety of experiments and metrological solutions, including interferometric measurement in micropositioning systems.

Singlemode standards at VACOM:

Transmission wavelengthCore/ mode field diameterNACladdingPlug in
633 nm3,7 µm / 4,4 µm0,12125 µmFC/APC
780 nm4,6 µm / 5,5 µm0,12125 µmFC/APC
850 nm4,9 µm / 5,9 µm0,12125 µmFC/APC
1310 / 1550 nm8,0 µm / 9,5 µm0,12125 µmFC/PC & FC/AP

On request, we can also carry out the optical fibre feed-through with your special fibre. In this case, please contact our customer service.

The OFDs with integrated multimode fibres manufactured by VACOM are designed for the respective wavelength ranges specified. As standard, VACOM manufactures fibres with a core diameter of 50µm, 200µm, 400µm and 600µm. They cover many applications in the ultraviolet (UV), visible (VIS) and near infrared (NIR) spectrum. The fibres with core diameters from 200µm to 600µm have a step-shaped refractive index (step index fibres). The fibre type MM50 is a graded index fibre, which minimises mode dispersion due to an optimised refractive index profile.
Multimode fibre feedthroughs are manufactured by VACOM in the FSMA connector version. The only exception is the MM50 fibre, which is available in FC/PC and FC/ACP versions. This fibre requires very high precision in core alignment. This small-core fibre is often used in the field of confocal metrology. Since back reflections from the ferrules' interfaces can have a negative effect when using this fibre, it is recommended to use the FC/APC connector system.
Due to the compact design in combination with the integrated coupling, which ensures the highest plug-in precision, and excellent behaviour in vacuum, the OFDs for multimode fibres developed and manufactured by VACOM are used in a variety of problem solutions. Examples include measurement technology in micropositioning, confocal experiments and spectroscopic investigations.

Multimode standards at VACOM:

Transmission wavelengthCoreNACladdingPlug in
450-2100 nm50 µm0,2125 µmFC/PC & FC/APC
190-1100 nm200 µm0,22220 µmUV variant, FSMA
400-2400 nm200 µm0,22220 µmIR variant, FSMA
190-1100 nm400 µm0,22440 µmUV variant, FC/PC, FSMA
400-2400 nm400 µm0,22440 µmIR -Variante, FC/PC, FSMA
500-2600 nm400 µm0,36 440 µmIR variant doped with Ge, FC/PC, FSMA
190-1100 nm600 µm0,22660 µmUV variant, FSMA
400-2400 nm600 µm0,22660 µmIR variant, FSMA

On request, we can also carry out the optical fibre feed-through with your special fibre. In this case, please contact our customer service.

OFD extended - Optical fibre feedthroughs for the highest demands

In order to meet the high demands of our customers from top-level research, we developed the OFD extended in the product line of optical fibre feedthroughs. With our adhesive-free sealed and low-outgassing optical fibre feedthrough, you are ideally equipped for the use of optical measurement technology under demanding environmental conditions, such as high temperature and radiation exposure as well as low pressures in the XHV range.
Our complete in-house production allows you a flexible choice of optical fibre, which we adapt to your specific needs. In addition, we can freely configure the position and number of feedthroughs per flange. We adapt the optical interface exactly to your individual application.

In the field of optical fibre feedthroughs, the following new advantages result for you:

  • Adhesive-free hermetically sealed
  • High temperature resistance (bakeable up to 250°C, 482°F )
  • High radiation resistance (10 MGy for 1 ½ months)
  • High reliability (proven by various in-house ageing tests).
  • Specification up to VACOM® Purity Class 4 & Vacuum Class XHV1


Various singlemode and multimode fibres are established as standards at VACOM. Please refer to the sections OFD Singlemode and OFD Multimode for more information. On request, we can also carry out the optical fibre feed-through with your special fibre. 

OFD for cryogen conditions

Our optical fibre feedthroughs for cryogenic applications are ideal for your applications in high and ultra high vacuum (HV and UHV) up to a temperature of liquid nitrogen (77 K). They are used, for example, in optical signal transmission to cooled detectors in astrophysics and material characterisation.
We place the highest demands on our feedthroughs in terms of cleanliness, insertion loss and vacuum suitability. The fibre cables can be dismantled on both the vacuum side and the atmospheric side and can be replaced when worn.
Our customers trust our product because of the low and comparatively reproducible insertion loss as well as the high-quality workmanship, which quickly leads you into UHV. We achieve these results thanks to outstanding expertise in vacuum-compatible design and our efficient cleaning processes. We can guarantee fast delivery thanks to a standardised modular system.
Do you have special requirements, such as an individual fibre, fibre bundles or increased optical specifications? Take advantage of our many years of experience in the planning and production of vacuum components and design your individual implementation together with us. Just give us a call!

Technical data:

Flange material:316L stainless steel
Flange type:KF, CF and ISO / Nominal sizes: 16 to 63 (1/2" to 2 1/2")
Operating temperature:Rough temperature up to 77K
Max. heating and cooling rate:3 K / min
He leakage rate:max. 10-10mbar l/s (depending on flange) (7.5 · 10-11 Torr/s)

Accessories for optical fibre feedthroughs

With the accessories for optical fibre feedthroughs available from us, you can realise a complete solution consisting of fibre cable usable on the atmosphere side, feedthrough and fibre cable suitable for vacuum. In particular, the fibre cables listed in our product catalogue represent only a small part of the product range and are only listed as examples for the SM1310 fibre in a few combinations of cable length and connector configuration.
The fibre cables available from us are available for all standard fibres in any length and with many possible connector types. We would be pleased to offer you a solution specially adapted to your needs.

In addition, we are happy to offer you special accessories, e.g. for cleaning connectors.

Samples of products

    Fiberoptic cable UHV | 321417
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    Singlemode, SM1310, FC/PC Pro | 300173
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    Multimode, MM600UV, FSMA Pro | 334290
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