Low Loss Optical Coupler
Original Publication Date: 1980-May-01
Included in the Prior Art Database: 2005-Feb-13
Modulated light sources for high frequency optical data transmission are typically edge-emitting diodes operating in either the laser or LED (light-emitting diode) regime. Current laser devices are very costly and have relatively poor life, but exhibit low divergence of emitted light. On the other hand, LEDs are presently of relatively low cost and exhibit long life, making them good candidates for optical data transmission applications. LEDs, however, are more like Lambertian emitters and couple poorly to single fiber cables which have characteristically small acceptance angles (typically 10 degrees or an N.A. of About 0.2). A "best case" LED/fiber situation is shown in Fig. 1, considering the emitting surface 10 of the LED 12 as a nearly point source.