Optical transmission method and apparatus using ofdm

Abstract

In order to achieve a higher spectral efficiency of OFDM sub-bands, optical signals using orthogonal frequency division multiplexing are transmitted through an optical network in the form of a continuous waveband optical signal. An optical add/drop multiplexer () splits the continuous waveband optical signal into an express path and a drop path. A band pass filter () is provided in the drop path to extract a sub-band carrying at least one of said OFDM modulated optical signals (DROP). The band pass filter () has a filter bandwidth that covers the sub-band to be extracted. A band-stop filter () is provided in the express path to remove the sub-band to be extracted from the continuous waveband optical signal (IN). The band stop filter () has a filter bandwidth which is narrower than the band pass filter (). An OFDM modulated optical add signal (ADD) can be added into the wavelength gap created through the band stop filter (). The sub-band carrying the optical add signal (ADD) occupies a wavelength range which is completely covered by the filter bandwidth of the band-stop filter (). The difference between the filter bandwidths of the band pass filter () and the band stop filter () corresponds preferably to the slope of the filter edges of the filters ().