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Overview: fiber coupled LED
Fiber – coupled LED modules and their applications
When LED light is to be used in fiber optic systems for sensing, lighting or data transmission, the LED light emitted into the entire half space must be coupled to the optical fiber of choice. The fiber chip coupling design can be optimized under different aspects.
- Depending on the fiber diameter and numerical aperture (NA) and the LED chip size, beam shaping optics (parabolic reflectors or lenses) may be useful. If fiber diameter and LED surface diagonal are nearly equal, precise butt coupling is a better solution.
- Optimizing the efficiency or alternatively the maximum light output in the fiber leads to different, constructive solutions: optimized efficiency generates a high energy efficiency design e.g. for mobile devices, maximum optical power even with poor efficiency can be a condition for some system concepts.
- The coupling of a POF fiber with a maximum thermal resilience of 85°C to a LED chip that can assume much higher temperatures, limits the design options. However, viable and attractive solutions exist, if heat dissipative designs are applied.
- If fiber bundles instead of single fibers are used, the uniform illumination of each single fiber in the fiber bundle is an additional requirement. For textile applications each individual fiber in the bundle must have equal brightness.
- Special requirements as a waterproff design of the fiber chip coupling setup occur mainly in textile applications, because the system must be functional even after washing cycles in a washing machine.
Frequently requested standard applications among all options for fiber-chip coupled modules are:
- pigtailed LED modules for data transmission,
- POF fiber coupled modules to illuminate very small areas in sensor applications,
- modules to homogenize the light power of LED emitters, e.g. for projection systems (see PowerLED Pointer),
- fiber coupled LED modules in combination with fiber splitters to realize multi wavelength light emitters (RGB modules),
- for fiber optic power transmission.
The following pictures show an overview of some typical and frequently requested LED modules for coupling to fiber optics: