Which of the following statements about QPSK modulation are false?

In QPSK, one phase represents two bits, which is also equivalent to splitting a data stream into two, reducing the data rate by half.

QPSK assigns two possible phase values in the optical field. This decreases the baud rate of optical signals by half while keeping the line rate unchanged.

ePDM-QPSK is a preferred modulation format for 100G WDM transmission.

QPSK modulation can increase the spectral bandwidth, reduce the OSNR requirement and non-linear effects in optical fibers, and improve the dispersion tolerance and PMD tolerance.