Abstract: An apparatus comprising an optical receiver configured to receive a plurality of orthogonal frequency-division-multiplexed (OFDM) symbols comprising a first OFDM symbol and a second OFDM symbol, and a processor coupled to the optical receiver and configured to generate a first decoded signal based on the first OFDM symbol, estimate a plurality of channel parameters adaptively based on the first decoded signal, generate a second decoded signal based on the second OFDM symbol, wherein the second decoded signal is generated using the plurality of channel parameters, and wherein phase recovery is performed on the first OFDM symbol using a number of pilot subcarriers prior to generating the first decoded signal.

Abstract: A method of optical communication comprising encoding four modulated symbols to generate four encoded symbols in two orthogonal polarizations and transmitting the four encoded symbols in two successive time slots. An optical communication apparatus comprising a processor configured to receive two sequences of digital symbols in a plurality of time slots, wherein the two sequences correspond to two components of two orthogonal polarizations, wherein one digital symbol per polarization is received in each of the plurality of time slots, divide each of the two sequences into a plurality of groups using a modulo operation of time, wherein each group comprises two digital symbols received in two consecutive time slots, and adaptively equalize the four digital symbols of the two consecutive time slots using a 4×4 matrix to generate four modulated symbols, wherein the 4×4 matrix comprises 16 tap-vectors.

Abstract: A method of optical communication comprising encoding four modulated symbols to generate four encoded symbols in two orthogonal polarizations and transmitting the four encoded symbols in two successive time slots. An optical communication apparatus comprising a processor configured to receive two sequences of digital symbols in a plurality of time slots, wherein the two sequences correspond to two components of two orthogonal polarizations, wherein one digital symbol per polarization is received in each of the plurality of time slots, divide each of the two sequences into a plurality of groups using a modulo operation of time, wherein each group comprises two digital symbols received in two consecutive time slots, and adaptively equalize the four digital symbols of the two consecutive time slots using a 4×4 matrix to generate four modulated symbols, wherein the 4×4 matrix comprises 16 tap-vectors.

Abstract: The present disclosure provides a method and system for fine estimation of a local oscillator frequency offset of a received signal at a coherent receiver, by evaluating the probability mass function (PMF) of the signal phase of output symbols at different frequencies. At frequencies other than the actual frequency offset, the signal phase is uniformly distributed in [??,?] such that the summation of square of PMF (PMF sum-square) values is minimized. However at the actual frequency offset, the signal phase is no longer uniformly distributed over [??,?]; in other words the signal phase will take some specific values in [??,?], therefore a peak PMF sum-square value will result. This peak PMF value provides an indication of the actual offset frequency of the received signal.

Abstract: System and method embodiments are provided for bit loading for optical Discrete Multi-Tone Transmission (DMT). In an embodiment, a method for bit loading for optical DMT transmission or reception includes receiving, at a processor, a bit data stream, wherein the bit data stream comprises a plurality of subcarriers; assigning, with the processor, a code rate to each of a plurality of forward error correction (FEC) encoders/decoders according to a mapping of a signal-to-noise-ratio (SNR) to a code rate for each of the subcarriers or subcarrier groups, wherein each FEC encoder/decoder corresponds to a respective one of the subcarriers or a respective subcarrier group; and assigning, with the processor, a modulation format to each subcarrier or each subcarrier group according to a mapping of an SNR for each subcarrier or subcarrier group to a bit number for a corresponding subcarrier or subcarrier group.

Abstract: An apparatus comprising an optical receiver configured to receive a plurality of orthogonal frequency-division-multiplexed (OFDM) symbols comprising a first OFDM symbol and a second OFDM symbol, and a processor coupled to the optical receiver and configured to generate a first decoded signal based on the first OFDM symbol, estimate a plurality of channel parameters adaptively based on the first decoded signal, generate a second decoded signal based on the second OFDM symbol, wherein the second decoded signal is generated using the plurality of channel parameters, and wherein phase recovery is performed on the first OFDM symbol using a number of pilot subcarriers prior to generating the first decoded signal.

Abstract: A method of optical communication comprising encoding four modulated symbols to generate four encoded symbols in two orthogonal polarizations and transmitting the four encoded symbols in two successive time slots. An optical communication apparatus comprising a processor configured to receive two sequences of digital symbols in a plurality of time slots, wherein the two sequences correspond to two components of two orthogonal polarizations, wherein one digital symbol per polarization is received in each of the plurality of time slots, divide each of the two sequences into a plurality of groups using a modulo operation of time, wherein each group comprises two digital symbols received in two consecutive time slots, and adaptively equalize the four digital symbols of the two consecutive time slots using a 4×4 matrix to generate four modulated symbols, wherein the 4×4 matrix comprises 16 tap-vectors.