
while carefully tailored low-pass characteristics yield higher tolerances to CD at
the expense of a typically 1- to 2-dB back-to-back sensitivity penalty relative to
NRZ-OOK [184] (cf. Table 2.2). A typical low-pass filtered electrical signal,
measured at 10.7 Gb/s, is shown as an inset to Figure 2.15. This three-level
signal is used to drive a chirp-free MZM between its transmission maxima,
where the outer levels generate the –1 symbols and the center level generates
the 0 symbol. When detected by a square-law photodetector, the negative
portion of the optical field is mapped on top of the positive portion, resulting
in the binary optical intensit ...