Study On The Technology Of Coupling Laser Diode To Graded-core Fiber

Laser Diode(LD) has been the most popular laser because of its obvious advantages. After it appeared, the fiber communication has been carried out and rapidly developed, which has been considered as the basic instruments of information. However, the output optical field of LD is elliptic instead of circular, so how to couple LD to optical fiber is an intractable problem. At present, a lot of coupling methods have been presented in many papers. Each has its merit: some are applied to simple mode fiber; others are applied to multi-mode fiber. They are depended on the characteristic of the LD's optical field and the fiber's Numerical Aperture(NA). This article includes the following segments: 1. The basic theories are offered which include the optical transmission theory in fiber and the characteristic of LD's optical field. 2. The coupling methods are compared and classified. 3. A new coupling system is present in this article. A section large core silica optical fiber is used in this system, one end coupled with semiconductor laser is fused into a sphere, the other end coupled with other optical systems is pulled into graded-core fiber. 4. The new coupling system is used to couple LD. Results proved that the coupling efficiency is about 75% and theoretically the tolerant disturbance of the coupling system is increased, so the difficult of debugging and encapsulation is reduced.