Optical transmission unit

U.S. Patent Number: 5825518

Abstract: An AM signal source frequency-multiplexes and outputs a plurality of AM signals. A soft clipper, which is formed by an amplifier or the like, nonlinearly loosely limits a large amplitude portion (impulsively changed portion) of the frequency-multiplexed AM signal by using its saturation property. Thereafter, an attenuator performs level adjustment for setting the signal at a prescribed degree of optical modulation. On the other hand, a 16QAM signal source frequency-multiplexes and outputs a plurality of 16QAM signals having different carrier frequencies. A frequency multiplexing part further frequency-multiplexes the AM multiplex signal with the 16QAM multiplex signal. An optical transmitter intensity-modulates a laser output beam with the frequency multiplex signal from the frequency multiplexing part and transmits the same. No clipping distortion occurs at this time. An optical signal from the optical transmitter is transmitted to a receiving system through an optical fiber member and is demodulated.

Inventors: Maeda; Kazuki (Neyagawa, JP), Masuda; Koichi (Hirakata, JP), Nakata; Hiroaki (Hirakata, JP)

Assignee: Matsushita Electric Industrial Co., Ltd. (Osaka-fu, JP)

Application Number: 08/613,226

Issued: 1998-10-20

Expired: 2006-10-20

Classes: 398/76 ; 398/183

Field of search: 359/124-125,132-133,181-183,161,134

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