Patent ID: 7831118

Claim:
A coarse wavelength division multiplexing optical transmission system, comprising: an optical transmission terminal including a plurality of first optical transmitters which generate a plurality of optical signals arranged on a first wavelength grid corresponding to a coarse wavelength division multiplexing system and a first multiplexer which multiplexes the optical signals output from said first optical transmitters to send out a coarse wavelength division multiplexed light to a transmission path; and an optical reception terminal including a first demultiplexer which demultiplexes the coarse wavelength division multiplexed light transmitted from said optical transmission terminal via the transmission path and a plurality of first optical receivers which receive optical signals of respective wavelengths output from said first demultiplexer, wherein at least one wavelength on said first wavelength grid is set as an additional wavelength; said optical transmission terminal, in place of said first optical transmitter corresponding to said additional wavelength, is provided with an additional light transmission unit including: a plurality of second optical transmitters which generate a plurality of optical signals arranged within a passband including said additional wavelength of said first multiplexer, on a second wavelength grid corresponding to a dense wavelength division multiplexing system, and a second multiplexer which multiplexes optical signals output from said second optical transmitters to output a dense wavelength division multiplexed light to said first multiplexer, and also provided with an optical attenuator which attenuates the dense wavelength division multiplexed light output from said additional light transmission unit so that the total power of the dense wavelength division multiplexed light sent out from said additional light transmission unit via said first multiplexer to the transmission path is approximately equal to the power per one wavelength of the optical signals, which are output from said first optical transmitters, corresponding to wavelengths other than said additional wavelength; and said optical reception terminal, in place of said first optical receiver corresponding to said additional wavelength, is provided with an additional light reception unit including; a second demultiplexer which demultiplexes the dense wavelength division multiplexed light output from said first demultiplexer, and a plurality of second optical receivers which receive optical signals of respective wavelengths output from said second demultiplexer, and also provided with an optical amplifier which amplifies the dense wavelength division multiplexed light output from said first demultiplexer at a gain according to an attenuation amount of said optical attenuator, wherein the first wavelength grid has an inter-wavelength larger than a dense inter-wavelength of the second wavelength grid.