A dual-polarization, 2-subcarriers code orthogonal, orthogonal frequency division multiplexed signal carrying information bits is transmitted in an optical communication network without transmitting a corresponding pilot tone or training sequence. A receiver receives the transmitted signal and recovers information bits using a blind equalization technique and by equalizing the 2-subcarriers OFDM signal as a 9-QAM signal in time domain with a CMMA (constant multi modulus algorithm) equalization method.

A transmission device that improves data reception quality includes: a weighting synthesizer that generates a first precoded signal and a second precoded signal from a first baseband signal and a second baseband signal, respectively; a phase changer that applies a phase change of i to the second precoded signal; an inserter that inserts a pilot signal into the second precoded signal applied with the phase change; and a phase changer that applies a phase change to the second precoded signal applied with the phase change and inserted with the pilot signal. satisfies /2 radians<< radians or radians<<3/2 radians. Each of the first baseband signal and the second baseband signal is modulated via a modulation scheme of quadrature amplitude modulation (QAM) using non-uniform mapping.

A modulator and a modulation method using a non-uniform 16-symbol signal constellation are disclosed. The modulator includes a memory and a processor. The memory receives a codeword corresponding to a low-density parity check (LDPC) code having a code rate of 3/15. The processor maps the codeword to 16 symbols of the non-uniform 16-symbol signal constellation on a 4-bit basis.

A dual-polarization, 2-subcarriers code orthogonal, orthogonal frequency division multiplexed signal carrying information bits is transmitted in an optical communication network without transmitting a corresponding pilot tone or training sequence. A receiver receives the transmitted signal and recovers information bits using a blind equalization technique and by equalizing the 2-subcarriers OFDM signal as a 49-QAM signal in time domain with a CMMA (constant multi modulus algorithm) equalization method.