Frequency-Packed Multiband-Coherent Transceiver With Symbol Rate-Adaptive Nyquist WDM Signals

In the next-generation flexible point-to-multipoint optical networks such as optical access systems, it is desirable for one transceiver to handle various Internet-of-Things traffic streams. A symbol rate-adaptive multiband-coherent-transceiver, that can transmit and receive wavelength division multiplexing (WDM) signals arranged at the Nyquist spacing after Nyquist spectrum shaping, achieves flexibility by changing the number of subbands (SB) and the symbol rate per SB. Band-asymmetric coherent access systems with wide bandwidth optical transceivers on the optical-line-terminal side and narrowband optical transceivers on the optical-networking-unit side have been reported for uplink and downlink transmissions. We also examined the multiband-coherent-transceiver for ultra-dense WDM signals with a narrow analog-device bandwidth and narrow SB spacing to improve cost and spectral efficiency. To the best knowledge of the authors, there is no other research on a Nyquist spectrally shaped WDM-passive optical network system that applies these two functions and flexibly changes the symbol rate per SB with a SB spacing less than the Nyquist spacing.