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FEMTO offers the FST flange for all photoreceivers which are available as FS version.  You have the choice between a 1.035″-40 threaded flange, including coupler ring with 30 mm outer diameter (FST) and a 25 mm unthreaded flange (FS).  Both types offer a broad compatibility with optical standard accessories like tubes, lenses, cage systems, optical adapters etc. from various manufacturers.

The FST version can be easily converted to an optical fiber input using the optional available PRA-FC or PRA-FSMA fiber-adapters.  Please note, that FEMTO recommends the fiber adapters only for photoreceivers with photosensitive area of 0.4 mm diameter or more.  Coupling efficiency may be compromised for photodiodes with smaller diameter.

PRA-FC or PRA-FSMA Fiber-Adapters

PRA-FC Adapter  |  PRA-FSMA Adapter  | PRA-FCA Adapter

  • Compatible with all FEMTO photoreceivers with threaded 1.035”-40 free space input
  • Easy mounting option for standard optical fibers
  • Recommended for photosensitive areas of 0.4 mm diameter or more
    (coupling efficiency may be compromised for photodiodes with smaller diameter)
  • Machined from solid stainless steel
  • Available adapter types: PRA-FC (FC/PC, FC/APC, FC/UPC) and PRA-FSMA
  • Other types on request

1.035″-40 Threaded Input now available for all FEMTO Photoreceivers

All FEMTO photoreceivers offered with FS input (round flange with 25 mm diameter) are now also available with 1.035″-40 threaded flange (FST) input – for even more flexibility on the optical bench!

The new external threaded free-space input (FST) will be delivered together with a matching internal threaded coupler ring offering a broad compatibility with lenses, tubes, cage systems and other accessories from various manufacturers. For example converting the free-space FST input to an optical fiber input is easily done by screwing on the optionally available FEMTO fiber adapters (PRA-FC and PRA-FSMA). A helpful tool for doing this would be the convenient spanner wrench AT-W1.

FEMTO fiber adapters are recommended for photosensitive areas of 0.4 mm diameter or more (coupling efficiency may be compromised for photodiodes with smaller diameter).

Existing FEMTO photoreceivers with FS-input can be converted to FST-input by FEMTO. Please contact us for further information.

If the connector you need is not listed below, please contact EOC’s technical support.


  • Allows use of the same photoreceiver for free-space and fiber applications

Model: Fiber Connector Types




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