Multimode-fiber technology for digital transmission

Multimode-fiber systems are presently being installed to meet some of the burgeoning demands for digital transmission in the telecommunications industry. These first-generation systems operate near 0.85-µm wavelength with laser transmitters and avalanche-photodiode receivers. Second-generation multimode systems may use simpler and more reliable LED´s and p-i-n photodiodes operating near 1.3 µm, where fibers exhibit much lower loss and dispersion. This paper summarizes the state of the art of multimode-fiber digital transmission with special emphasis on emerging technologies for operation in the 1.1-1.7- µm wavelength region. Graded-index multimode fibers, lasers, LED´s, photodetectors, receiver sensitivities, and noise penalties are considered. Finally, some of the requirements and challenges in applying these technologies are discussed.