An Introduction to Large Core Optical Fibers

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:

 

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.