Abstract

All the 1.3-μm zero-dispersion single-mode fibers (SMFs) and 1.3-μm optical transmitters in today's CATV networks will be used continuously over a long period of time. Therefore, when a larger optical power budget is required for deeper fiber penetrations in the near future, using 1.3-μm optical amplifiers may be more economically and technically viable than using 1.55-μm erbium-doped fiber amplifiers (EDFAs). Parallel to the evolution process of deep fiber penetration in the subscriber loop will be the matured development of M-ary quadrature-amplitude-modulation (M-QAM) modems and MPEG-I1 codecs, and the gradual replacement of a11 AM-VSB video channels by M-QAM digital video channels. Consequently, it is of great interest to see if potentially low-cost semiconductor optical amplifiers can be used to transport multiple channels of ITU-standardized 64-QAM signals. The feasibility of transmitting 33 channels of 64-QAM signals by using a directly modulated 1.3μm DFB laser and a semiconductor optical amplifier has been recently demonstrated.¹ In this paper, we demonstrate that the system power budget can be significantly increased by using an external modulation system.

© 1996 Optical Society of America