Patent ID: 7203422

Claim:
An optical wavelength-division multiplexing access system, in which a center unit (OSU) and a plurality of n optical network units (ONUs) are connected via a wavelength splitter and optical fiber transmission lines, and downstream optical signals from the OSU to the respective ONUs and upstream optical signals from the respective ONUs to the OSU are transmitted in both directions, wherein: at least between the OSU and the wavelength splitter, the central wavelengths (the central frequencies) of the downstream optical signals which correspond to the ONUs are selected at will from within an equally spaced wavelength grid (an equally spaced frequency grid) which is determined by a uniform wavelength spacing of Δλd (a uniform optical frequency spacing of Δfd), and their wavelength errors (optical frequency errors) are set to be within ±Δλd/2 (±Δfd/2); at least between the wavelength splitter and the OSU, the central wavelengths (the central frequencies) of the upstream optical signals which correspond to the ONUs are selected at will from within an equally spaced wavelength grid (an equally spaced frequency grid) which is determined by a uniform wavelength spacing of Δλu (a uniform optical frequency spacing of Δfu), and their wavelength errors (optical frequency errors) are set to be within ±Δλu/2 (±Δfu/2); the wavelength spacing Δλd (the optical frequency spacing Δfd) of the downstream optical signals is set to twice or more the wavelength spacing Δλu (the optical frequency spacing Δfu) of the upstream optical signals; and each of the ONUs transmits an upstream optical signal whose optical spectral width is twice or more Δλu (Δfu), and the wavelength splitter spectrum slices the upstream signals which have been transmitted from the ONUs into wavelengths (optical frequencies) whose optical spectral widths are mutually different within Δλu (Δfu), and also wavelength-division multiplexes the spectrum-sliced signals and transmits the multiplexed signal to the OSU.