| 摘要 |
A coherent optical system includes an optical coupler or combiner (138) for combining a received upstream optical signal and an optical local oscillator signal. The coherent optical system further includes a coherent optical receiver (114) which is configured to receive and process the combined optical signal from the optical coupler to retrieve upstream information from the upstream optical signal. In certain embodiments, the coherent optical communication system includes a central office (102) having an optical source (110) for generating a composite downstream optical signal made up of downstream optical signals of particular wavelengths (or sets of wavelengths). A downstream optical signal having a particular wavelength (or set of wavelengths) is routed to a downstream destination with a portion of the downstream optical signal (after modulation with upstream information) being returned to the central office as an upstream optical signal of the particular wavelength (or set of wavelengths) which is part of a composite upstream optical signal. At the central office, the optical coupler or combiner (138) combines the received upstream optical signal and the optical local oscillator signal, and the coherent optical receiver (114) processes the combined optical signal. Thus, the coherent optical system can alleviate the problems and costs associated with generating the local oscillator signal because the same or a similar source is readily available. Using the same or similar optical source to generate the downstream optical signals and the local oscillator system permits an increase in capacity without the additional cost of wavelength-registered and stabilized optical sources at the subscriber locations. <IMAGE> |
