Digital subcarrier multiplexing for flexible spectral allocation in optical transport network.

We demonstrate a spectrally efficient digital subcarrier multiplexed (DSCM) coherent optical system for optical transport network. In the proposed system, mutually orthogonal subcarrier channels are digitally generated, which allows a high degree of flexibility in bandwidth allocation and scalability in data rate granularity. The receiver can also dynamically change the number of DSCM channels for detection without changing the system configuration. We experimentally investigate the transmission performance of a 22.2 Gb/s DSCM system with 10 subcarrier channels using QPSK modulation. The impacts of channel spacing and time mismatch between subcarrier channels are also explored.