Reduction of Modal Noise in High-Speed Short-Distance Computer Data Links by an Electrical Signal

It is important to minimize modal noise in shortdistance computer data links made with multimode fibers. It is known that modal noise may be efficiently eliminated by reducing the coherence of a high-speed semiconductor laser using a high frequency auxiliary signal added to the normal data signal. To avoid other system impairments, such as intermodulation distortion, the optimum frequency, and amplitude of this auxiliary microwave signal must be known. This paper presents measured and calculated data on the trade-offs between modal noise reduction and intermodulation penalty. A 2.4-Gb/s link experiment illustrates the benefits of this method. © 1991 IEEE