| 摘要 |
A comb splitting system demultiplexes and/or multiplexes a plurality of optical signal channels at various wavelengths. The comb splitting system has at least two interconnected successive stages of wavelength division multiplexers (WDMs). A WDM of a first stage communicates bands of channels to respective WDMs of the second stage via suitable optical paths. Each of the bands has a plurality of the individual channels that are separated by at least one other of the channels. Each second stage WDM, which is allocated to a particular band, is interconnected to optical paths, each for carrying one or more individual channels. Furthermore, in accordance with a significant feature of the present invention, the bandpasses and bandpass periodicity (free spectral range) associated with the first stage WDM are smaller than the bandpasses and bandpass periodicity associated with the second stage WDMs. The foregoing feature has numerous advantages. The second stage WDMs are less expensive and physically smaller than the first stage WDM. Crosstalk between channels is reduced. The alignment of the WDM passbands with the wavelengths of the transmitters/receivers in a central office is simplified. Later stages of WDMs can tolerate larger fabrication errors, do not require flat passbands and birefringence compensation, and can tolerate full environmental temperature variations without feedback control in the central office.
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