News Brief: In radar turntables, ROV thrusters, medical CT scanners, and construction machinery slewing platforms, there is an inconspicuous component that determines whether the entire machine can “transmit while rotating” — the slip ring. In the past, it only handled power conduction; later, encoders and Ethernet were added; now, fiber optics are becoming one of the core channels in high-end electro-optical hybrid slip rings. In this issue, we take a closer look: exactly how many types of electrical signals can a fiber optic slip ring “team up” with, and to what extent can the “gas + electricity + liquid +optic” all-in-one integration go today?
I Why Fiber Optic Slip Rings Are in the Spotlight
Traditional electrical slip rings rely on metal brushes sliding over copper rings to transmit current and signals, but they struggle with three things:
- · High-speed data: Gigabit Ethernet, high-definition video, radar echoes, Camera Link;
- · Long distances: Backhaul over tens to thousands of meters, where electrical signal attenuation becomes unbearable;
- · Strong electromagnetic interference: Near variable-frequency drives, motors, and welding equipment, copper wires act like antennas.
Fiber optic rotary joints (FORJ) use light instead of electricity to transmit data. They inherently offer high bandwidth, low loss, EMI resistance, and support single-mode/multi-mode switching. Therefore, a common approach in high-end equipment is to “let the electrical slip ring supply power and low-speed signals, while the fiber optic slip ring handles high-speed data,” with both systems stacked on the same rotating shaft.
II What “Electrical Signals” Can Fiber Optics Combine With? A Quick List
1. Power Electricity
- 2A / 5A / 10A / 20A signal and power rings
- High‑voltage, high‑current up to 3300V / 720A (thruster grade)
- Low‑voltage 24V / 220V / 480V control and servo power supply
Typical combo: N channels of fiber + several channels of power, allowing a turntable to supply power to a pod while rotating.
2. Industrial Ethernet & Data
- 100M Ethernet (100Base‑T)
- Gigabit Ethernet (1000Base‑T)
- Industrial Ethernet: PROFINET, EtherNet/IP, EtherCAT, Modbus/TCP
- USB 2.0 / USB 3.0
Fiber carries the “high‑speed backbone,” while electrical rings supplement the “control command loop.”
3. Fieldbus & Serial Ports
- RS232 / RS422 / RS485
- CAN / CANopen / CANbus
- Profibus‑DP
- DeviceNet / ControlNet / CC‑Link
- InterBus, Modbus RTU
Commonly used for servo drives, PLC remote I/O, and encoder feedback.
4. Servo / Encoder / Sensor
- Servo encoder cables (compatible with Yaskawa / Panasonic / Siemens servo systems)
- Resolver signals, excitation signals
Thermocouples, RTDs (PT100) - 4–20mA / 0–10V analog
- Temperature, pressure, load cell sensors
- SSI, BISS, TTL, SPI, I²C, UART, 1553B, 1394B
Electro‑optical slip rings are often configured as “1–36 channels fiber + dozens of weak‑signal electrical channels.”
5. Video / Audio / High Frequency
- CVBS / AHD / CVI / TVI analog high definition
- HD‑SDI / 3G‑SDI
- HDMI (19‑pin), VGA (9‑pin)
- Coaxial RF, microwave, RF rotary joints (can be embedded separately)
Common in electro‑optical pods, turntable surveillance, and broadcast vans.
6. Special Options
- Single‑mode / multi‑mode available (FC / SC / ST / LC / APC)
- Wavelength division, multi‑channel fiber (products with up to 120 channels have been seen)
- Gold‑to‑gold contacts, IP65–IP68, stainless steel housing, explosion‑proof housing
III “Gas + Electricity + Liquid + Optic” All-in-One
Doing “optical + electrical” alone is no longer novel; the real challenge is stacking “gas and liquid paths” as well, without cross‑contamination of media.
| Medium Type | Common Content | Remarks |
|---|---|---|
| Electric | Power + signal + Ethernet + bus | High/low voltage modules isolated |
| Optical | Single-mode/multi-mode fiber, RF fiber | Expandable from 1 to 120 channels |
| Gas | Compressed air, nitrogen, vacuum, steam | Vacuum lines count as one channel |
| Liquid | Hydraulic oil, coolant, water, cleaning fluid | Pressure limit depends on sealing |
| High Frequency | RF, microwave, SDI rotary joints | Used with or instead of fiber |
Typical All-in-One Structures
- Stacked type: Electrical slip ring + fiber optic ring + pneumatic/hydraulic rotor stacked in sections for easy modular maintenance
- Coaxial nested: Central through‑bore for shaft, pneumatic/hydraulic ports distributed on the periphery
- Separate type: Fiber optic rotary joint (FORJ) physically separated but coaxial with the electrical slip ring
- Large‑aperture through‑bore: Inner diameter 500–1000 mm, convenient for cable and pipe routing (top drives, winches)
IV Typical Application Scenarios
- Ocean engineering / ROV: 3300V/720A + 6-ch fiber + IP68 316L housing.
- Military radar / Pod: Gigabit Ethernet + HD-SDI + GJB150A testing.
- Medical CT / Surgical arm: High channel count, low-noise precious metal contacts.
- Construction machinery: Power 20A + compressed air + fiber video.
- Packaging / Semiconductor: Ethernet + bus + servo + vacuum nozzles.
- Oil top drive: High current + hydraulics + salt-spray resistance.
V. Summary: Evolution to “Rotary End Systems”
Early = conductive rings → Later = + encoders → Today = Optical + Electrical + Gas + Liquid.
For equipment manufacturers, this means:
- Centralized and controllable failure sources at the shaft end
- Higher overall protection rating
- Reduced wiring costs for large systems
- Competitive domestic alternatives for deep sea, military, and medical sectors
Post time: Oct-20-2026