CROSS-REFERENCE TO RELATED APPLICATIONS

Encoding PAM4 or PAMS symbols to have a power spectral density (PSD) similar to the PSD of a standard 8b 10b Non-Return-to-Zero stream. In one embodiment, a transmitter includes first and second 8b 10b encoders that receive first and second streams split from an original byte stream. The first and second 8b 10b encoders output first and second 8b 10b streams, respectively. The first and second 8b 10b streams are fed into a 2 -bit combiner that performs a linear combination of the first and second 8b 10b streams. And a 4 -level Pulse Amplitude Modulation encoder (PAM4 encoder) converts the linear combination of each two bits, received from the combiner, into a PAM4 symbol. Wherein the resulting stream of PAM4 symbols has PSD similar to the PSD of the standard 8b 10b non-return-to-zero stream. 对PAM4或PAM8符号进行编码，使其功率谱密度(PSD)类似于标准8b10b非归零流的功率谱密度。在一个实施例中，发射器包括第一和第二8b10b编码器，其接收从原始字节流分离的第一流和第二流。该第一和第二8b10b编码器分别输出第一和第二8b10b流。该第一和第二8b10b流被馈送到执行该第一和第二8b10b流的线性组合的2位组合器。4电平脉冲幅度调制编码器(PAM4编码器)将从该组合器接收的每两个位的线性组合转换成PAM4符号。其中P