Silica optical fiber has to be protected by some coating in order to prevent it from mechanical damage, moisture or other contaminants. In many cases, various types of polymers, such as Tefzel™, Polyamide, Nylon, or Acrylic are appropriate for sufficient protection.
Image Credit: Shutterstock/Valentyn Vokov
However, there are many special fiber applications in which the fiber may be exposed to high mechanical stress, acidic chemicals and high temperature, which can damage the polymer coating and lead to fiber breaks, as polymers are dissolved by many acids, their maximal operating temperature is not more than 125 °C, and such coating permits atmospheric moisture to penetrate in the fiber.
Metal-Coated Silica (MCS) Optical Fibers
All the benefits of silica polymer-clad (PCS) fibers are present in their hermetically sealed Metal-Coated Silica (MCS) optical fibers. Other major improvements include increased mechanical strength and greater fatigue resistance compared to non-hermetic PCS fibers. Based on a NIR or UV silica fiber core choice the transmission spans over a spectral range of 200 to 2400 nm. MCS also remains stable in corrosive chemicals that generally react to silica glass.
Types of MCF
Two types of MCF are produced: Cu-alloy-coated and Al-coated fibers. The temperature range is from: -270 °C to 400 °C for Al-, and -270 °C to 600 °C for CU-alloy coatings with a humidity range of up to 100%.
Cu and Al-coated fibers are the optimal solution when used in vacuum, high temperature, and severe environmental conditions. No additional protective polymer coating is required for metal coatings. Thus metal coating has no contender in applications for which the presence of a polymer coating is unwanted. Real life applications, such as sensors, aerospace, chemical industry, and deep-well oil-field industry, can belong to several groups at the same time:
- Enhanced-reliability fiber optic devices in which fibers are soldered to connectors (e.g. devices for the space industry)
- Fiber optic sensors of temperature, vibration
- High-temperature alarm systems remain functional in accidental conditions (e.g. in case of fire)
- High-temperature fiber optic systems resistant to hydrogen penetration intended for applications in the oil-field and chemical industries
- Radiation-resistant fiber optic systems meant for use in the nuclear industry (e.g., image guides for visual inspection of nuclear installations, plasma diagnostic systems in thermonuclear installations)
- Fiber bundles-combiners to combine the power of hundreds diode lasers in a single beam
Al & Cu-coated fibers. Image credit: Art Photonics GmbH
Cu coated fiber bundle-combiner. Image credit: Art Photonics GmbH
This information has been sourced, reviewed and adapted from materials provided by art photonics GmbH.
For more information on this source, please visit art photonics GmbH.