Staas & Halsey
Direct modulation phase shift keying (DM-PSK) transmission system
 A direct modulation phase shift keying transmission system (DM-PSK transmission system) is disclosed for coherent optical fiber transmission in which an injection current supplied to a semiconductor laser is adapted to be directly modulated. This system presents useful features in automatic frequency control, demodulation, and phase noise suppression. 
Fujitsu Limited
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Terumi Hideo Takao Shigeki
Chikama Kuwahara Naito Watanabe