In its standard form CSRZ is generated by a single Mach–Zehnder modulator (MZM), driven by two sinusoidal waves at half the bit rate BR, and in phase opposition.
The signal format Alternate-Phase Return-to-Zero (APRZ) can be viewed as a generalisation of CSRZ in which the phase alternation can take up any value ΔΦ (and not necessarily only π) and the duty cycle is also a free parameter.
CSRZ can be used to generate specific optical modulation formats, e.g. CSRZ-OOK, in which data is coded on the intensity of the signal using a binary scheme (light on=1, light off=0), or CSRZ-DPSK, in which data is coded on the differential phase of the signal, etc.
The characteristic properties of an CSRZ signal are those to have a spectrum similar to that of an RZ signal, except that frequency peaks (still at a spacing of BR) are shifted by BR/2 with respect to RZ, so that no peak is present at the carrier and power is ideally zero at the carrier frequency (hence the name).
Compared to standard RZ-OOK, the CSRZ-OOK is considered to be more tolerant to filtering and chromatic dispersion, thanks to its narrower spectrum.