Foley & Lardner
SCM type of optical signal transmission system without clipping distortion
 A subcarrier multiplexed type of optical signal transmission system includes a transmitting unit, a receiving unit, and a single optical fiber. The transmitting unit includes a plurality of multiplexing circuits, each of which frequency-division-multiplex of analog image signals to produce an electric signal; a plurality of modulating units provided for the remaining multiplexing circuits, wherein each of the plurality of second modulating units performs analog-modulation of an optical oscillation signal in accordance with the electric signal without clipping to produce an optical signal; and a coupling unit for combining the optical signals to produce a transmission optical signal which is to be transmitted onto a single optical fiber. In this case, a distributed feedback type semiconductor laser is preferable as each of the plurality of modulating units. Further, each of the plurality of modulating units is preferably provided with an optical isolator at the output side for preventing a reflected optical signal from being inputted. In order to prevent any clipping distortion, it is preferable that an optical modulation is small for each of the plurality of modulating units, e.g., semiconductor lasers and an effective analog-modulation index of the optical oscillation signal in each of the remaining modulating units is equal to or less than 20%. 
NEC Corporation
H
H04J
inventional
Hirohito
Yamada