112Gb/s optical transponder with PM-QPSK and coherent detection employing parallel FPGA-based real-time digital signal processing, FEC and 100GbE Ethernet interface

A simple three-stage carrier phase estimation algorithm for 16-QAM systems based on QPSK partitioning and maximum likelihood detection

“…With the development of very large scale integration technologies, higher order modulation formats with digital signal processing (DSP) algorithms based on optical coherent detection have been applied to optical fiber communication systems, which can increase the transmission capacity and compensate linear impairments and non-linear impairments in electrical-digital domain. For example, polarization multiplexing quadrature phase shift keying (PM-QPSK) based on optical coherent detection, has been commercially applied for 100 Gbps optical fiber communication systems due to its high tolerance to phase noise and high performance for long haul transmission [6]. For M-PSK optical coherent systems, carrier phase recovery based on a Viterbi and Viterbi phase estimation (VVPE) algorithm employing the M-th power scheme can effectively eliminate phase noise [7].…”

Experimental comparison of PS-QPSK and LDPC-coded PM-QPSK with equal spectral efficiency in WDM transmission

“…However, this will lead to a more complex system and it should be noted that PS-QPSK can be decoded on a symbol-bysymbol basis requiring similar receiver and transmitter complexity as PM-QPSK. Most demonstrations of realtime coherent receivers exclude the FEC circuits with a few exceptions 6 , leading to the question of acceptable complexity of the decoder. Several fiber-optic transmission experiments utilizing LDPC codes have been demonstrated with for instance 16-QAM 7 , 3-ary phase-shift keying 8 , PM-QPSK 9 , and 24-dimensional extended Golay coded modulation 10 .…”