Reconfigurable Optical Network Intermediate Node With Full-Quadrature Regeneration and Format Conversion Capacity

In this paper, a reconfigurable optical network intermediate node scheme with format conversion capacity and full-quadrature regeneration functionality is proposed. With a degraded input quadrature phase-shift keying (QPSK), the proposed network node can be dynamically reconfigured based on the network situation to output a QPSK or a four-level pulse amplitude modulation (PAM4), both full-quadrature regenerated. The input QPSK is first converted into the two full-quadrature regenerated binary phase-shift keying tributaries after phase sensitive amplifier-based quadrature de-multiplexing and selfphase modulation-based amplitude regeneration. Then the output regenerated QPSK or PAM4 are generated through vector addition by tuning the relative phase and amplitude between two tributaries. For an input 20 Gb/s QPSK with optical signal-to-noise ratio (OSNR) of 15 dB, the output regenerated QPSK gets 10.4% decrease in error vector magnitude (EVM), 2 dB receiver OSNR improvement at the bit error rate of 10
^-3
, and regeneration factors of 6.4 dB and 3.7 dB in amplitude and phase, respectively. In the case with regenerated PAM4 as the output, compared with the input QPSK, it has 10.4% improvement in EVM and regeneration factors of 7.1 dB and 2.5 dB in amplitude and phase, respectively. The numerical simulation results reveal that the system effectively regenerates input signal in full-quadrature with format conversion capacity. The proposed node scheme can be applied as a fullquadrature QPSK regenerator between optical networks, which both employ QPSK to increase the transmission distance, or an alloptical interconnection node between different optical networks where different modulation formats are used individually.