8-way, 70-km transmission of 33-channel 64-QAM signals utilizing 1.3-/spl mu/m external modulation system and semiconductor optical amplifier

Parallel to the evolution process of deep fiber penetration in the CATV subscriber loop will be the matured development of M-ary quadrature amplitude-modulation (M-QAM) modems and MPEG-II codecs, and the gradual replacement of all 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 1.3-/spl mu/m DFB laser and a semiconductor optical amplifier has been recently demonstrated. In this paper, we demonstrate that the system power budget can be significantly increased by using an external modulation system.