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An Introduction to Large Core Optical Fibers

Posted by George Zhu on Thu, Sep 28, 2017 @ 10:09 AM

The most common multimode optical fibers, which allow multiple light modes to propogate along the link simultaneously, are designed with a core diameter size of 50µm for for high-speed communications networks.  You may recognize these types of fibers by industry specifications such as OM2, OM3, and OM4 or by brand names like Corning® ClearCurve® and OFS® LaserWave®.

However, for applications that require greater power transmissions using a high-power laser source, multimode fiber with a larger core diameter is a more suitable approach.  For example, a continuous-wave laser with power of 50W or above would require an optical fiber with a minimum core diameter of 100µm.

One important characteristic of a fiber is the power handling ability, measured in Watt/cm2.  For silica core fiber, its limit ranges from a few hundred KW/cm2 to 1MW/cm2 depending upon the glass type and dopants used1.  As the fiber's effective area increases, the ability to transmit a source with a higher power intensity also increases.  Thus, a large core fiber is the ideal choice for some medical (theraputic, surgical) and as well as some industrial (welding, cutting) high-power lasers.

To visually demonstrate the core size difference between a standard 50µm multimode fiber and a 100µm large core multimode fiber, see Figure 1 below:

Large Core Fiber Diagram.jpg

Similar to the standard multimode types, large core fibers are also manufactured and optimized for operation at the 850nm and 1300nm wavelengths.  Below is a table showing some of the most common core/cladding combination offerings for large core fibers:

     Core (µm)      Cladding (µm) 
100 125
100 500
200 500
300 500
400 500
600 750
800 1000

If you are seeking more information about large core optical fibers, or have a requirement for specialty fibers, contact the engineering team at M2 Optics at your convenience.


References:

1. http://www.horiba.com/uk/scientific/products/fibre-optics/technical-information/high-power-fibre-optics/

Topics: optical fibers, specialty optical fibers, medical fibers, high power lasers, large core fibers, multimode optical fibers