ABSTRACT
This chapter outlines the general principle, benefit, application range and limitation of the phase-conjugated twin wave (PCTW) technique. It discusses effective PCTW’s modifications and phase-conjugated coding techniques to reduce the spectral redundancy and increase the flexibility of the original PCTW ideology. In PCTW-based transmission, the first-order nonlinear distortion is cancelled and the amplified spontaneous emission noise power is reduced by a factor of two as a consequence of coherent superposition. The PCTW technique should be considered as a technique for improving the system performance, such as distance reach and signal’s quality rather than improving the total capacity. One important shortcoming of the PCTW technique is that it sacrifices half the transmission capacity. The Phase-Conjugated Subcarrier Coding (PCSC) technique can also be applied effectively in wavelength-division-multiplexing coherent optical orthogonal frequency division multiplexing transmission. The fiber nonlinearity impairments in COOFDM transmission can be mitigated by processing neighboring subcarriers simultaneously using the PCSC scheme.
