Coupling Efficiency of LED to Fiber Optic Guide

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SUMMARY

The coupling efficiency of surface mount LEDs (SMD LEDs) to cylindrical optical guides is influenced by several factors, including the LED's light distribution, the fiber's diameter, and the index of refraction. SMD LEDs exhibit a cosine distribution of light intensity, which affects how effectively light can be injected into the fiber. High-power diodes require optics to match the emitting area with common fiber sizes, while multimode fibers utilize internal reflections for light transmission. The discussion highlights the importance of using lenses and antireflective coatings to optimize energy transfer efficiency.

PREREQUISITES
  • Understanding of SMD LED light distribution patterns
  • Knowledge of optical fiber types and their refractive indices
  • Familiarity with coupling techniques for LEDs and optical fibers
  • Basic principles of light propagation in multimode fibers
NEXT STEPS
  • Research the impact of lens design on LED to fiber coupling efficiency
  • Explore antireflective coating technologies for optical components
  • Study the characteristics of different types of optical fibers, including graded-index fibers
  • Investigate methods for measuring coupling efficiency in LED-fiber systems
USEFUL FOR

Engineers and researchers in the fields of optoelectronics, fiber optics, and lighting design who are looking to optimize the performance of LED systems coupled with optical fibers.

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Homework Statement
Most surface mount types of LED’s have a very nearly cosine distribution of light intensity. If we desire to inject light from an LED to the end of a cylindrical optical guide, what is the coupling efficiency as a function of distance (x) from the end of the guide?

Assume that the LED is a point source and that the fiber has a diameter D
Relevant Equations
I found that the half cone angle let's call it theta=arctan(D/2x)
Now that I know theta, I'm trying to use that to calculate the coupled light.

What unit am I looking for, is it luminous intensity? I'm thinking I have to integrate from 0 to theta but I'm not sure what the integral looks like. Any ideas?
Most surface mount types of LED’s have a very nearly cosine distribution of light intensity. If we desire to inject light from an LED to the end of a cylindrical optical guide, what is the coupling efficiency as a function of distance (x) from the end of the guide?

Assume that the LED is a point source and that the fiber has a diameter D
 
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Pretty vague question, lacks purpose. SMD LEDs come in a variety, some with lenses some wirhout. LED range from infrared to ultraviolet with corresponding changes to LED and interface.

Laser purpose ranges from illumination to indicator to laser diode. Low power diode has small chip and less diff between emitter and fiber diam. High power is larger emmitting area requiring optics to make beam fit in common fiber sizes.

The fiber type (index of refraction, etc.) Is an important variable. Two examples: on circuit board indicators with plastic "rods" from front panel to top of led on circuit board; fiber-optic communication/networking with laser coupled to graduated refractive index fiber that keeps light centered.

Multimode fiber typically uses fiber's internal reflections. Both plug fiber directly into the LED part. Since you don't mention using lenses and antireflective coatings, efficency of energy transfer from LED and fiber is not a concern.
 
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Agreed. I asked the OP via PM to post datasheets and diagrams, but no joy so far...
 
Thanks for the input guys. That's all the information I have hence why I asked for help. but I figured it out after trying a few things
 

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