| 摘要 |
In a duplex WDM transmission system, an optical amplifier that uses different amplification paths (22, 25) for amplification of the different directions of signal propagation requires filters (34, 37) to keep the loop gain less than unity for all wavelengths within the amplification waveband. Simple high-pass and low-pass filters can be used when red channels are used for signals propagating in one direction, and blue ones for those propagating in the other. Comb filters are, however, required for use in any optical amplifier employed such a transmission system using any form of interleaved form of channel allocation in place of the red/blue allocation. Examples of such amplifiers are described, these amplifiers having flitters possessing an arrayed waveguide grating structure (44). <IMAGE> |
