| 摘要 |
An optical transmission system utilizes optical single-sideband (SSB) modulation and incorporates at least one mid-span analog SSB regenerator arranged to produce a phase conjugation of the transmitted signal. The phase conjugation technique, referred to here as complementary sideband regeneration (CSR), is accomplished on the retransmitted optical signal in the electrical domain, and requires no nonlinear optical techniques. If the phase conjugation is performed at the mid-point between two identical spans of optical fiber, all even orders of chromatic dispersion are automatically compensated. In addition, distortion effects incurred as a result of the square-law detection of the SSB signal are reduced by inverting the signal in the transmitter included in that regenerator. The simultaneous correction of chromatic dispersion and SSB distortion is accomplished using a four-span transmission with CSR in each regenerator and signal inversion occurring in the first and third regenerator. Three mid-span analog SSB regenerators are interposed between four interconnected optical transmission line spans. The regenerators are (a) spaced essentially evenly along the entire length of the optical transmission medium, and (b) arranged with electrical receivers and transmitters that (i) receive an SSB signal on one sideband (upper or lower) (ii) transmit the SSB signal on the other sideband (lower or upper, respectively), and (iii) "flip" or invert the signal in the first and third regenerators. The inversion can be accomplished by appropriately controlling the sign of the modulator bias voltage in a MZ modulator.
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