How to achieve automatic stopping of fiber optic sensors

Automatic stopping with fiber optic sensors is achieved by integrating the sensor with a controller that detects interruptions in the optical path and triggers a fail-safe shutdown of machinery.

How Fiber Optic Sensors Work

Fiber optic sensors detect physical changes by modulating light transmitted through an optical fiber. The system typically includes a light source, optical fiber, sensing element, and detector. When the sensor detects a change—such as an object blocking the light beam—the optical signal is altered, and the detector converts this change into an electronic signal that can trigger a response, such as stopping a machine . Fiber optic sensors can be intrinsic, where the fiber itself is affected by the measurand, or extrinsic, where an external transducer modulates the light . Hybrid sensors combine both approaches.

Components for Automatic Stopping

To achieve automatic stopping, fiber optic sensors are paired with a controller designed for emergency stop functionality. For example, the Micronor MR380-0 OEM Controller operates over a duplex multimode fiber link and continuously transmits light. If the optical path is blocked, the fiber is broken, or power is lost, the controller defaults to an emergency state, automatically stopping connected machinery . The controller provides digital logic or open-collector outputs to activate external relays or safety circuits.

Implementation Steps

1. Select the appropriate sensor type: Choose intrinsic, extrinsic, or hybrid fiber optic sensors based on the application and environmental conditions.
2. Install the optical fiber and sensing element: Position the fiber so that any hazardous intrusion or abnormal condition interrupts the light path.
3. Connect to a compatible controller: Use a controller like the MR380-0 that can interpret the optical signal and trigger a fail-safe output.
4. Configure outputs for machine control: Connect the controller outputs to relays, motor drives, or safety circuits to stop machinery automatically.
5. Test and validate: Ensure the system meets safety standards such as ISO 13850, NFPA 79, and ISO 13849-1, confirming that the automatic stop functions reliably under all expected conditions .

Safety Considerations

• Fiber optic emergency stop systems are inherently safe for explosive or harsh environments because they use optical signals rather than electrical currents .
• The system should be manually reset after activation to prevent accidental restarts while hazards are present .
• Redundant design and high-quality components improve reliability, ensuring the automatic stop works when needed . By combining fiber optic sensors with a dedicated controller and proper installation, machinery can achieve automatic stopping in response to hazards, enhancing safety and compliance with industrial standards.