Fibre optic rotary joints
Senring FO Series fibre optic rotary joints
Single and multi-channel fibre optic rotary joints with 1 to 8 channels, single-mode (9/125 µm, 1310/1550 nm) or multimode (50/125 or 62.5/125 µm), rated over 100 million revolutions, also in hybrid versions with up to 96 electrical circuits.
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Key specifications
| Outer diameter | 6.8–86 mm |
|---|---|
| Fibre channels (max) | 8 |
| Rated life (revolutions) | over 100 million (2–3 million for signal channel models) |
| Fibre | SM 9/125 µm; MM 50/125 or 62.5/125 µm |
| Wavelength | 1310/1550 (SM); 850/1310 (MM) |
| Hybrid circuits max | 96 |
Summarised in our own words from SENRING Electronics Co., Limited's published data; series maxima, individual models vary. Last checked 2026-10-30. Source 1
Notes on this data
Insertion loss, speed, IP and temperature not published on the page.
Specify Motion is not affiliated with SENRING Electronics Co., Limited. Senring and FO Series fibre optic rotary joints are used only to identify the product. Comparisons use published figures; always confirm against the current datasheet.
Senring FO Series fibre optic rotary joints replacement and alternative options
Use these supply-network options as a starting point for an engineering check. We can also help source the original Senring part. Published series figures do not establish an exact-model or drop-in replacement: confirm ratings, fit, interfaces and approvals for your application.
Fibre optic rotary joints that carry single-mode or multi-mode optical channels across rotation for high-bandwidth, interference-free data. Channel counts run from one to fifty.
| Published maximum | FO Series fibre optic rotary joints | FR Series Fiber Optic Rotary Joint |
|---|---|---|
| Speed | — | 2,000 rpm |
| Fibre channels | 8 | 50 meets or exceeds |
Hybrid units combining fibre optic channels with power and signal circuits, used on electro-optical pod systems.
Figures are the highest published for each series and are not always measured the same way. A higher figure is not automatically a better choice: mounting, duty cycle, feedback, connectors and approvals matter too. An engineer will check the fit against your application before recommending anything.
Typical applications
What a fibre optic rotary joint is
A fibre optic rotary joint, or FORJ, is the optical equivalent of a slip ring: it passes light signals between a fixed and a rotating fibre without a physical join. In a single-channel unit the two fibre ends sit on the rotation axis with collimating lenses so the beam crosses a small gap. Multi-channel units use a derotating optical element, such as a Dove prism, so several fibres can share the axis. Joints are built for single-mode or multimode fibre and can be combined with electrical slip rings.
When engineers choose a fibre optic rotary joint
Choose a FORJ when the rotating part needs very high bandwidth, immunity to electromagnetic interference or long transmission distances, as in subsea vehicles, cable reels, radar and video systems. It is passive and wear is very low because nothing touches. The trade-offs are insertion loss, which must fit the optical budget, sensitivity to contamination and a higher cost for multi-channel units. If data rates are modest and EMC is manageable, an electrical Ethernet slip ring may be simpler.
How to specify the Senring FO Series fibre optic rotary joints
Send these with your enquiry and an engineer can confirm the right FO Series fibre optic rotary joints variant or an equivalent:
- Number of optical channels
- Fibre type: single-mode or multimode, core size (µm)
- Operating wavelengths (nm)
- Maximum insertion loss and loss variation during rotation (dB)
- Return loss requirement (dB)
- Connector type, such as FC, ST, LC or SC
- Speed (rpm), environment and any electrical circuits to combine
Common mistakes to avoid
- Not including the FORJ insertion loss in the full link optical budget
- Mixing single-mode and multimode fibres between the joint and the transceivers
- Leaving connectors uncapped during assembly, which contaminates the optical faces
- Specifying many channels when wavelength multiplexing would cut cost and size
Senring FO Series fibre optic rotary joints: frequently asked questions
Can you help replace Senring FO Series fibre optic rotary joints or source the original?
Send the full model code, quantity and required date. Our engineers can check original-part availability and assess suitable alternatives, including Motion Control Products options where appropriate. We confirm compatibility and any changes needed before recommending a replacement.
What is the Senring FO Series fibre optic rotary joints?
Single and multi-channel fibre optic rotary joints with 1 to 8 channels, single-mode (9/125 µm, 1310/1550 nm) or multimode (50/125 or 62.5/125 µm), rated over 100 million revolutions, also in hybrid versions with up to 96 electrical circuits. Published series figures include outer diameter 6.8 mm, outer diameter 86 mm, fibre channels 8. It is made by SENRING Electronics Co., Limited; Specify Motion can help source it or propose an equivalent.
Who makes the Senring FO Series fibre optic rotary joints?
The Senring FO Series fibre optic rotary joints is made by Senring (SENRING Electronics Co., Limited) and is listed here for engineers comparing options. Specify Motion is not affiliated with SENRING Electronics Co., Limited; brand names are used only to identify the product.
What is the outer diameter of the Senring FO Series fibre optic rotary joints?
The published series minimum outer diameter is 6.8 mm. Individual models and sizes in the FO Series fibre optic rotary joints range vary, so check the exact variant against your duty cycle, mounting and environment, or ask our engineers to confirm the right size for you.
Is there an alternative to the Senring FO Series fibre optic rotary joints?
We can assess suitable replacement options. On published figures, Motion Control Products FR Series Fiber Optic Rotary Joint and Motion Control Products Fiber Optic Integrated Electrical Slip Ring are options to assess from our supply network. An engineer confirms the fit against your application before recommending anything.
What is the difference between single-mode and multimode fibre optic rotary joints?
Single-mode joints carry light in one guided mode through a very small core, which suits long distances and high data rates but needs precise alignment. Multimode joints use a larger core, which is more tolerant of alignment and suits shorter links. The joint must match the fibre and transceivers already used in the system, so state the fibre type and wavelength.
Can a fibre optic rotary joint be combined with an electrical slip ring?
Yes. A common arrangement places the FORJ on the axis, with the electrical slip ring built around it in a through-bore format, so power and optical data pass through one assembly. This is widely used on cable reels, ROVs and radar. Specify the electrical circuits and optical channels together so the supplier can design one housing and sealing system.
Further reading: How to select a fibre optic rotary joint · How to select a slip ring · Slip rings
Other fibre optic rotary joints series
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