An optical bypass switch is a network device that automatically reroutes optical fibre traffic around a failed or powered-off node in daisy chain and ring topologies, maintaining end-to-end fibre continuity in under [SWITCHOVER_TIME] without manual intervention or network protocol convergence. In industrial OT environments — power substations, water treatment plants, and transportation infrastructure — fibre networks frequently use daisy chain wiring where a single node power failure can isolate all downstream devices. ORing's IBS-102FX series optical bypass switches address this single-point failure risk at the physical optical layer, complementing software-based redundancy protocols such as O-Chain and MSTP.
The problem: single-point failure in daisy chain and ring topologies
Network redundancy protocols such as O-Ring, O-Chain, STP, and RSTP are effective at rerouting traffic around failed links — but they require at least one redundant physical path to exist. Two common industrial topologies lack this safety net:
Daisy chain topology
In a daisy chain, switches are connected in series: Device A → Switch 1 → Switch 2 → Switch 3 → Device B. There is only one physical path between devices. If Switch 2 loses power, all communication between Switch 3 and Device B is completely severed — no redundancy protocol can restore it because there is no alternative path. The network remains broken until Switch 2 is repaired or replaced.
Ring topology with multiple failures
A ring topology provides one level of redundancy: if a single link or node fails, traffic reroutes around the ring. However, if two or more nodes fail simultaneously, the ring is split into isolated segments that cannot communicate with each other. This scenario is particularly relevant in industrial environments subject to power outages, where multiple switches in the same power zone may lose power simultaneously.
| Topology | Single node failure | Two-node failure | Optical bypass helps? |
|---|---|---|---|
| Daisy chain | ❌ Network severed downstream | ❌ Network severed at both points | ✅ Yes — bypasses each failed node |
| Ring (single) | ✅ Traffic reroutes around ring | ❌ Ring splits into isolated segments | ✅ Yes — prevents ring splits |
| Ring + O-Ring/MSTP | ✅ Sub-20 ms recovery | ❌ Cannot recover without physical path | ✅ Yes — maintains physical path through failed nodes |
How an optical bypass switch works
An optical bypass switch is installed alongside each network node (switch or router) that requires protection. It has four optical ports: two network ports (connected to the upstream and downstream fibre path) and two monitor ports (connected to the protected node's optical interfaces).
Normal operation (node powered on)
In normal operation, the bypass switch routes optical signals from each network port through to the corresponding monitor port and into the protected node. Data flows: Network Port 1 → Monitor Port 1 → Node → Monitor Port 2 → Network Port 2. The node processes traffic normally; the bypass switch is transparent to the network.
Failure state (node powered off or failed)
When the protected node loses power, a passive relay inside the bypass switch automatically activates — with no external power or control signal required. The relay mechanically reconnects the two network ports directly: Network Port 1 → Network Port 2. Optical traffic now passes straight through the bypass switch, completely bypassing the failed node. Connectivity to all downstream devices is maintained.
Switchover from normal to bypass state occurs in under [SWITCHOVER_TIME]. The bypass switch also activates a relay output ([RELAY_SPEC]) that can be wired to an alarm panel, PLC, or SCADA system to trigger an immediate power failure alert.
Optical bypass switch vs software redundancy protocols
Optical bypass switches and software redundancy protocols solve different problems and are typically deployed together rather than as alternatives:
| Feature | Optical bypass switch | Software redundancy (O-Ring / MSTP) |
|---|---|---|
| Failure type addressed | Node power failure | Link failure or node failure (with redundant path) |
| Requires redundant path? | No — bypasses on same fibre | Yes — needs alternative physical route |
| Works in daisy chain? | ✅ Yes | ❌ No redundant path exists |
| Recovery time | [SWITCHOVER_TIME] (physical layer) | < 20 ms (O-Ring) / < 1 s (MSTP) |
| Operating layer | Layer 1 — physical optical | Layer 2 — data link |
| Power dependency | Passive — activates on power loss | Requires powered nodes to run protocol |
| Alarm output | ✅ Relay output for SCADA integration | SNMP trap / syslog (requires network) |
The recommended architecture for critical industrial fibre networks is to deploy optical bypass switches at each node in the daisy chain or ring, combined with O-Ring or O-Chain on the switches themselves. The bypass switch handles physical-layer continuity during power failures; the redundancy protocol handles link-level rerouting during normal operation.
ORing IBS-102FX optical bypass switch — model comparison
The IBS-102FX series is available in single-mode and multi-mode variants to match the fibre type deployed in the network:
| Specification | IBS-102FX-SS-LC (Single-mode) | IBS-102FX-MM-LC (Multi-mode) |
|---|---|---|
| Fibre type | Single-mode (9/125 µm) | Multi-mode (50/62.5/125 µm) |
| Wavelength | [SS_WAVELENGTH] nm | [MM_WAVELENGTH] nm |
| Max transmission distance | [SS_DISTANCE] | [MM_DISTANCE] |
| Connector type | LC duplex | LC duplex |
| Bypass switchover time | [SWITCHOVER_TIME] | [SWITCHOVER_TIME] |
| Relay output | [RELAY_SPEC] | [RELAY_SPEC] |
| Operating temperature | [TEMP_RANGE] | [TEMP_RANGE] |
| Typical application | Long-distance inter-building fibre, substation rings | Short-distance intra-building fibre, factory floors |
For full datasheets, see the IBS-102FX series product page.
Industrial use cases for optical bypass switches
Power substation fibre protection ring (IEC 61850)
Protection relays and bay controllers in power substations are typically connected in a fibre ring using IEC 61850 GOOSE messaging, where microsecond-level timing is critical for protection coordination. An optical bypass switch at each IED (Intelligent Electronic Device) ensures that if any IED loses power during a fault clearance event, the fibre ring remains intact and other protection devices continue to communicate. The relay output simultaneously triggers the substation SCADA alarm.
Daisy chain wiring in factory automation
Long factory production lines frequently use daisy chain fibre wiring to connect machine controllers, vision systems, and HMI panels in sequence. Installing an IBS-102FX at each machine ensures that a single machine power-off — during maintenance, emergency stop, or fault — does not sever communication to all subsequent machines on the line. Production monitoring continues uninterrupted.
Railway trackside cabinet ring
Trackside signalling cabinets along a railway line are often connected in a fibre ring. Cabinet power may be cut intentionally for maintenance or unintentionally by track damage. Optical bypass switches ensure that taking one cabinet offline for servicing does not disrupt signalling communication to other cabinets along the ring.
Frequently asked questions
What is an optical bypass switch and how does it work?
An optical bypass switch automatically reroutes fibre traffic around a node when that node loses power. In normal operation, data passes through the node via monitor ports. On power loss, a passive relay connects the two network ports directly — bypassing the failed node and restoring fibre continuity in under [SWITCHOVER_TIME], without requiring network protocol convergence or manual cable changes.
What is the difference between an optical bypass switch and O-Ring or STP?
Software redundancy protocols (O-Ring, STP, MSTP) reroute traffic through an alternative network path — but require one to exist. In a daisy chain there is no alternative path; a single failure is permanent until repaired. An optical bypass switch operates at the physical fibre layer, bypassing the failed node on the same fibre path without needing a redundant route. The two technologies are complementary — see O-Chain configuration guide for combining both approaches.
How fast does the IBS-102FX restore connectivity?
The IBS-102FX restores optical path continuity in under [SWITCHOVER_TIME] — this is a physical-layer switchover that does not depend on network protocol convergence. The connected network devices may still require their own link re-establishment after the optical path restores.
What is the difference between single-mode (SS-LC) and multi-mode (MM-LC)?
Single-mode (IBS-102FX-SS-LC) supports long-distance fibre runs up to [SS_DISTANCE] at [SS_WAVELENGTH] nm — suited for inter-building and substation ring applications. Multi-mode (IBS-102FX-MM-LC) supports shorter distances up to [MM_DISTANCE] at [MM_WAVELENGTH] nm — suited for intra-building factory and warehouse cabling. Both provide the same bypass protection mechanism.
What does the relay output do?
The relay output ([RELAY_SPEC]) activates when the bypass switch triggers — i.e., when a connected node loses power. It can be wired to an alarm panel, PLC digital input, or SCADA system to trigger an immediate alert, allowing operations staff to respond to the node failure before any wider network disruption is noticed.
Related resources
- ORing IBS-102FX series optical bypass switches — product page
- How to configure O-Chain ring redundancy on ORing switches
- How to configure MSTP on ORing 9000 Series switches
- ORing industrial managed switches — product range
- What is IEC 62443?
- External: IEC 61850 — Communication networks and systems for power utility automation (iec.ch)
