Help needed: coupling light from a LED into an optical fiber

[gstuber]

First let me preface this by saying by physics-fu is remedial at best. I am a neuroscientist by training, but need a little help with piece of equipment I am designing, so any ideas or input would be greatly appreciated. Basically, I need to figure out a way to efficiently couple a light emitting diode ~2mm in diameter, emitting ~470 nm light at an angle of 20 degrees (the smallest emitting angle I have been able to find for a commercially available small LED) to a multimode fiber optic cable (200 um core diameter, 0.37 NA). I know that for efficiently coupling a light source to optical fiber, the light needs to be colliminated, but I am having a hard time figuring out to do this with commercially available couplers I have seen (most are for much longer wavelengths used in telecommunications). Also, it would really help if this coupling device would be as small and light as possible, preferably only a couple of mm in length and less than 2 mm in diameter. Again, if anyone has ideas or even advice on where to look or who to consult to build this, it would be greatly appreciated. I am willing to pay for custom design, however most of the companies I have contacted have not been that responsive. Thanks again for looking!

Garret

 

[DarioC]

I have some visible light fiber, a source, and liquid couplers put away from an experiment I was doing some time ago. I may be able to supply you with helpful information from my source catalog and other information from that experiment.
Do you need to couple only to your diode or do you just need to couple to some source?
The source I have is red visible, I will have to check for the wavelength.
The source I have is about the size of a smaller flashlight. AA cells as I remember.
Let me know if I can help. I worked with fiber-optics as a test/tech/engineer; (retired now.)
D

 

[astrokreng]

, as a neuroscientist, I understand that this may not be your area of expertise, but your background in science and problem-solving skills will definitely be helpful in finding a solution to your problem. Coupling light from a LED into an optical fiber can be a challenging task, but with some research and experimentation, it can be achieved.

One possible solution could be to use a lens to collimate the light from the LED before it enters the fiber optic cable. This can be done by placing the LED at the focal point of a convex lens, which will then collimate the light and direct it into the fiber. The size and shape of the lens can be chosen based on the specifications of your LED and fiber optic cable.

Another option could be to use a fiber optic coupler specifically designed for shorter wavelengths, such as the one used in medical imaging. These couplers are typically smaller in size and can efficiently couple light from a LED into a multimode fiber optic cable.

In addition, you may want to consider using a polarization preserving fiber optic cable to minimize losses and maintain the polarization of the light. This can be particularly useful if you are working with polarized light.

If you are unable to find a commercially available solution, you may want to consult with a custom design company or a university research lab that specializes in optics. They may be able to design and fabricate a custom coupler that meets your specific needs.

I hope this helps and wish you success in your project.