Patent ID: 7929862

Claim:
An optical transmission system comprising: a signal processing unit capable of implementing a scrambler upon a digital electric signal and thereby randomizing a code sequence of the digital electric signal, and outputting a scrambled digital electric signal; a first converting unit converting the scrambled digital electric signal into a digital optical signal; a second converting unit converting an analog electric signal into an analog optical signal; and a wavelength division multiplexing unit multiplexing, by wavelength division multiplexing, the analog optical signal and the digital optical signal, and transmitting the multiplexed optical signals to a user terminal, wherein a wavelength of the analog optical signal and a wavelength of the digital optical signal are such that the analog optical signal is influenced by an induced Raman Scattering of the digital optical signal, wherein the signal processing unit implements the scrambler of which a pattern period is equal to or greater than 500 nsec, wherein the analog electric signal includes a plurality of channels and one of the plurality of channels in the analog optical signal is affected by the induced Raman Scattering of the digital optical signal, and wherein the plurality of channels is located at an interval of 6 MHz, each of the channels has a gap from a neighboring channel, and an interval between frequency spectra of the digital optical signal into which the digital electric signal scrambled by the pattern period is converted is equal to or less than a width of the gap.