| 摘要 |
A multiple-access network communication system employs a single continuous-wave optical carrier which is successively modulated and multiplexed at a plurality of data access nodes. The data access nodes are cascaded along an optical propagation path, and at each such node, the optical carrier is impressed with an modulated electrical signal which corresponds to an electrical subcarrier having a subcarrier frequency which is uniquely responsive to its associated data access node. Local data at each such node is modulated electrically in accordance with a known modulation scheme, such as FSK modulation, the resulting modulated subcarrier being conducted to a respective optical modulator which impresses same upon the optical carrier. The optical carrier is periodically, with respect to the data access nodes, amplified by an optical amplifier, and ultimately conducted to a receiver where the optical carrier is detected and converted to a corresponding electrical signal. The electrical signal is then demultiplexed, illustratively by filters tuned to the subcarrier frequencies, each of which is then demodulated, whereby the original data signal is recovered. The invention can be implemented in bidirectional embodiments which permit modulated optical carrier to be propagated in opposite directions. In addition, a bidirectional embodiment can be provided with both optical carriers from a single laser source.
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