Flame Monitoring
Reliable safety under extreme conditions.
Optical fiber lances are an extension of flame monitoring systems and are ideal for applications with strong vibrations, limited space, or for use with tilting burners. They possess a high temperature resistance of up to 400 °C and consist of glass fibers within a flexible, robust cable that is protected against water, dust, acid, and temperature.
Optical Fiber Lance
Optical fiber lances feature high temperature resistance, are vibration-proof, and robust. This makes them ideal for the following applications:
- In locations with strong vibrations at the viewing position
- Limited space at the viewing position
- Ideal for tilting burners
The optical fiber has a temperature resistance of up to 400 °C. The glass fibers are encased in a flexible and robust cable with a steel braid and a silicone sheath. This protects the optical fiber from water, dust, as well as acid and temperature. For the optical fiber lances, glass fibers are available for all sensors and spectral ranges. The lengths of the lances depend on the local conditions and are determined in collaboration with the customer. The lance head contains an optic that focuses the flame signal onto the fiber optic bundle. The temperature resistance is 400 °C. The total length should not exceed 20 meters.
A fiber optic lance is a rigid tube with integrated optics that can be positioned very close to a flame. A lens at the tip focuses the flame light and directs it into a fiber optic cable. The lance is heat-resistant up to 400°C and is cooled with purge and cooling air. This allows for reliable flame monitoring, even in confined spaces or areas with high heat, vibrations, or tight spaces directly at the burner.
OE stands for “optoelectronic.” An OE transducer (also called a sensor or detector) converts the light transmitted via the fiber optic cable into an electrical signal that can be evaluated by the control system. It is safely located outside the danger zone. Only the robust fiber optic cable extends to the flame. Different OE transducers are optimized for different wavelength ranges (UV, visible, IR).
Construction
Optical fiber lances are custom-manufactured. The lance consists of a combination of rigid and flexible sections. Purging and cooling air is typically introduced in the rigid section. For maintenance, the optical fibers can be easily removed from the system and reinserted.
Applications
Optical fiber lances can be mounted directly at the fuel outlet of the burner assembly, thus capturing the flame radiation from a short distance. This achieves high flame intensity and security against extraneous light in multi-burner systems.
Flame monitoring is consistently ensured, especially with tilting burners that have a dynamic viewing position. Here too, monitoring is accomplished using the optical fiber lance. The lance head, with its integrated optics, is fixed at the burner mouth and always transmits the flame signal optimally. Purging and cooling air channels prevent the optical fibers and the optics from overheating.
In industrial furnaces, multiple flames often burn simultaneously. A monitoring system must be able to distinguish between “its” flame and the light from neighboring burners. Ambient light immunity describes how effectively the system filters out extraneous light. Due to its direct mounting at the burner mouth and the directional optics of the lance, the system detects only the flame of the assigned burner: a critical safety factor.
Why Choose Light Guides from FOS Inon Fiber Optics?
Quality “Made in Germany” pays off. Thanks to our proprietary manufacturing and testing processes, we offer custom solutions for numerous applications, from laboratories to aerospace.
Manufacturing Process
To ensure our light guides and fiber optic products meet the highest standards, we rely on a specialized manufacturing process. This allows us to guarantee exceptional chemical and tactile robustness so they can perform optimally in their respective environments. Precision is a critical factor in this, true to our motto: “Making the impossible happen.”
Materials Used
- Borosilicate: Glass with high temperature resistance and chemical resilience.
- PMMA (Polymethylmethacrylate): A thermoplastic, lightweight plastic with high light transmittance.
- Silica-Hard Clad: A robust plastic coating for improved strength and durability.
- Silica-Silica for UV and NIR Wavelengths: Our specialized glass fibers, optimized for the transmission of light in the ultraviolet (UV) and near-infrared (NIR) ranges.
PMMA is a thermoplastic material, known under brand names such as Plexiglas or acrylic glass. In fiber optics, PMMA is used for:
- Flexible, cost-effective fiber optic cables are used
- Large core diameters (up to several millimeters)
- Applications using visible light
PMMA fibers are less temperature-resistant than glass fibers (max. 70-100°C), but significantly more flexible and less expensive. This makes them a particularly good choice for lighting or sensors where extreme temperatures are not present.
Borosilicate (also called “boron glass”) is a special type of glass with a high boron oxide content. It is the same material used to make heat-resistant laboratory glassware and baking molds. In fiber optics, it offers:
- Excellent chemical resistance to acids and alkalis
- Good temperature resistance up to approximately 400-500°C
- Low thermal expansion (less stress during temperature changes)
Ideal for standard industrial applications and lighting.
Optional Specifications:
- Various apertures available
- Polarization can be maintained
- Anti-reflection coating possible
- Various lengths, diameters, bending radii, converters, and vacuum feedthroughs optional
- Various connectors and ferrules suitable for industry and medicine
SMA (Sub-Miniature A) is a standard screw-type connector for fiber optic cables, designed for laboratory equipment and spectrometers. The connector has a 1/4″-36 thread. FSMA is the fiber optic version with a specially protected ferrule for the sensitive fiber end face. Standardized connectors allow you to connect our cables directly to your equipment, or we can manufacture custom connectors for your specific application.
Silica-silica fibers consist entirely of high-purity quartz glass (silicon dioxide), both the core and the cladding. This construction offers:
- Extremely high temperature resistance up to 1000°C
- Optimal transmission in the UV range (below 300 nm)
- Excellent transmission in the NIR range (1000-2500 nm)
- Minimal absorption losses
Therefore, these fibers are primarily used in high-performance lasers, UV curing, and spectroscopy.
Technical Data
- Spectral Transmission: UV: 190 nm – 1200 nm | IR: 1100 nm – 2200 nm
- Temperature Range: -45°C … +400°C
- Ø Optical Fiber with Interlock Hose: approx. 17 mm
- Material: Stainless Steel
- Bending Radius: min. >125 mm
- Sighting Tube Connection: According to system specification
- Sensor Connection: According to customer specification
- Purge and Cooling Air: approx. 6 m³/h
Transmission describes how much light passes through an optical fiber, expressed as a percentage. A transmission of 99% means that 99% of the coupled light reaches the other end. Losses occur due to absorption within the material, scattering, and reflections at interfaces. High-quality fibers and precisely machined end faces minimize these losses, which is particularly important for long cables or low light power applications.
Learn More
Do you require further information, a customized quote, or expert consultation for your project? We are at your disposal at any time.
Reliability doesn’t happen by chance.
At FOS Inon Optics, quality is not just a promise—it is a standard that can be measured. Our development and manufacturing processes for fiber-optic systems are ISO 9001:2015 certified. This establishes the foundation for reliable performance, reproducible results, and trust wherever optical precision is critical.
