Due to the elliptical pattern of the laser diode, simply butting the fiber optic core up to it results in 10-20% efficiency or a 7-10 dB coupling loss.
Lenses can be used to increase the coupling efficiency, as spherical lenses compensate for the elliptical emission pattern of the diode.
The angle of the surface of the optical fiber can be placed at less than 10 degrees to prevent the reflection of laser light back into the diode, or use a surface with a small radius of curvature. Hyperbolic lenses are best used as a hemispherical surface doesn’t offer the best coupling. Grinding the tip of an un-tapered core helps to match the fiber.
[[Lensed and Tapered Fiber]] – most common coupling method.
Sources
- “Laser Diode to Fiber Coupling,” Fosco Connect. Accessed: Sep. 03, 2023. [Online]. Available: http://www.fiberoptics4sale.com/wordpress/laser-diode-to-fiber-coupling/
Backlinks
[[Fiber Lasers]]
Fiber Optic Networks
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