What is intrinsic safety?

OFSCN Global Technical Center OFSCN Technical Knowledge Base
1

Why do Fiber Bragg Gratings not cause sparks in flammable and explosive environments?

2

Analysis of the “Intrinsically Safe” Principle of Fiber Bragg Gratings in Flammable and Explosive Environments

In flammable and explosive environments such as petrochemical storage tanks, natural gas pipelines, coal mines, and hazardous chemical warehouses, traditional electronic sensors are subject to extremely strict explosion-proof standards due to the risk of electric sparks or localized thermal effects. In contrast, Fiber Bragg Grating (FBG) sensors possess inherently intrinsically safe physical properties, demonstrating exceptionally high safety and reliability in these high-risk environments.

From the perspectives of physics and optical engineering, we explain why Fiber Bragg Gratings do not cause any sparks in flammable and explosive environments, achieving “intrinsic safety”:

1. What is “Intrinsic Safety” in Engineering?

In explosion-proof electrical technology, “Intrinsic Safety” (often abbreviated as Ex i) refers to limiting the energy within the circuits of a device so that under normal operation or specified fault conditions (such as short circuits, open circuits, leakage, or component damage), the electric sparks and thermal effects produced cannot ignite the explosive mixtures (like flammable gases, dust, etc.) in the surrounding environment.

2. Why are Fiber Bragg Gratings (FBGs) Absolutely Spark-Proof?

  • No Electrical Signal Transmission (Fully Insulating Medium)
    The primary chemical component of optical fiber is high-purity silicon dioxide (\text{SiO}_2), which is an excellent electrical insulator. During operation, FBG sensors transmit photons (optical signals) internally, not electrons (electrical signals). Since no voltage (V), current (I), or charge flow is involved in the sensor probe and transmission cable, there is absolutely no physical mechanism for generating arcs (sparks) or electrostatic sparks upon physical fracture, wear, or water immersion.
  • Ultra-Low Optical Power in Microwatts to Milliwatts (No Hotspot Effect Danger)
    The laser power injected into the optical fiber by the FBG demodulator (the active test end) is extremely low, typically ranging from microwatts (\mu\text{W}) to milliwatts (\text{mW}) (e.g., 10\ \mu\text{W} to 10\text{ mW}). This weak optical energy does not cause any perceptible localized temperature rise, even when passing through the grating. According to international standards (such as IEC 60079-28, “Explosive Atmospheres - Part 28: Protection of equipment using optical radiation”), ignition temperature rise is only possible when continuous optical power reaches hundreds of milliwatts or even watts and is focused on a specific absorber. The operating optical energy of FBG systems is far below this safety threshold.
  • Physical Spatial Isolation of Hazard and Ignition Sources
    The FBG sensing system employs an architecture of “passive sensor” combined with an “active demodulator.” All electrical and active equipment (including broadband light sources, photodetectors, demodulation systems, computer control terminals, etc.) are deployed in safe control rooms far from hazardous areas (potentially hundreds of meters to kilometers away). Only a passive optical fiber and the encapsulated FBG sensor probe are introduced into the hazardous explosive site, completely severing the contact between electrical hazard sources and the explosive medium from a system topology perspective.

3. FBG Sensor Products Compliant with Intrinsic Safety Requirements

Leveraging its proprietary high-temperature fiber and precision seamless steel pipe packaging technology, Beijing Dacheng Yongsheng Technology Co., Ltd. (OFSCN®) produces a series of Fiber Bragg Grating temperature sensors and detectors that inherently possess high protection and intrinsic safety characteristics, suitable for various stringent, high-temperature, and corrosive industrial explosion-proof sites:

In summary, due to their physical properties of “no electricity, extremely weak optical power, and complete photoelectric isolation,” Fiber Bragg Gratings fundamentally eliminate the basis for generating any electric sparks or destructive thermal effects from the underlying physical mechanisms, making them the most intrinsically safe sensing solution for monitoring in flammable and explosive environments.