LD to MM fiber coupling

[mufc]

Hi,
Im designing a setup to focus the light from a 405nm laser diode into a multimode fiber (50 or 62.5/125), could anyone suggest a lens or lenses to do this? will i need 2 lenses, a collimator lens then a focusing lens or just the one?

Thanks

 

[ElektroFreak]

You can do it with a simple collimating lens in most cases. If the lens is used to focus the beam to a point rather than a collimated beam, the focal point will easily be small enough to fit inside the end of a fiber.

 

[mufc]

thanks for the quick reply, do you have any suggestions of actual lenses that could do this? cheaper the better but anything will be useful

 

[ElektroFreak]

Typically most hobbyists just use an Aixiz module (AixiZ) to hold the diode, which comes with an acrylic lens that works for just about any wavelength. If you wanted to do better, you could use a meredith module (Meredith Instruments) There are also glass lenses available that have been coated for 405nm here: AixiZ

 

[LarryDFW]

mufc;

You want to focus the laser beam to a diameter slightly less than the fiber diameter.

The better quality AR coated short F.L. lenses will deliver 10 to 30% more power to the fiber optic.

LarryDFW

 

[Kenom]

Unless your using just 1 fiber, this is going to be incredibly hard to do as the fibers in most cables are more than 1 fiber. Example being...

This means that your light output from your lens is going to miss approximately 20% or more of the fibers by going between them and around them.