3 Advanced aspects of optical modulations in achieving high bit rates and immunity to signal degradation
3.2 Convergence of networks: coexistence of amplitude and phase modulations in one fibre

Demand for higher information capacity and bit rates require upgrading existing optical systems or running more systems on one fibre. Then, new systems are added to existing systems and the fibre bandwidth is used in more efficient way. The coexistence of optical systems refers mainly to:

In many cases, each system running in a fibre uses different modulation format.

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Optical spectrum of DWDM with channel interleaving.