| CPC H04B 10/6162 (2013.01) [H04B 10/532 (2013.01)] | 14 Claims |
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1. A coherent optical receiver comprising:
a digital filter configured to compensate for a channel effect of a complex received symbol received from a coherent optical transmitter using a channel coefficient of a digital filter updated through an equalization algorithm, wherein the digital filter is a multi-tap digital filter having a multi-tap or a single-tap digital filter having a single-tap and comprises a first digital filter not interworking with a complex conjugate block and a second digital filter interworking with a complex conjugate block;
a symbol delayer configured to set a delay period of a complex received symbol for which the channel effect is compensated for through the digital filter, wherein the symbol delayer comprises a first symbol delayer interworking with the first digital filter and a second symbol delayer interworking with the second digital filter;
a complex adder configured to perform a complex addition operation on a complex received symbol for which a time delay is set through the symbol delayer and a complex received symbol that passes through the digital filter, wherein the complex adder comprises a first complex adder interworking with the first symbol delayer and a second complex adder interworking with the second symbol delayer;
a channel equalizer configured to correct a coefficient of the digital filter according to a channel change using a complex received symbol on which the complex addition operation is performed, by interworking with the complex adder; and
a parallel-to-serial converter configured to convert symbols in series recovered from a complex received symbol on which an addition operation is performed through the complex adder,
wherein the coherent optical transmitter is configured to place a first transmission symbol and a second transmission symbol comprising a symbol pair in an X polarization and a Y polarization in an odd-numbered symbol interval, respectively, place the first transmission symbol and the second transmission symbol to cross each other to be different from a position of a transmission symbol that is placed in the odd-numbered symbol interval for the X polarization and the Y polarization in an even-numbered symbol interval, and then perform a negative operation on a transmission symbol placed in the X polarization in the even-numbered symbol interval and perform a complex conjugate operation on a transmission symbol placed in one of the X polarization and the Y polarization.
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