Chromatic dispersion monitoring using four wave mixing of semiconductor optical amplifier

We propose and experimentally demonstrate an all-optical on-line chromatic dispersion (CD) monitoring technique for 40 Gbit/s return-to-zero on-off-keying (RZ-OOK) signal using the four wave mixing (FWM) effect of semiconductor optical amplifier (SOA). The received signal, whose carrier frequency is suppressed by a fiber bragg grating (FBG), is launched into the SOA together with a continuous wave. The optical power of one idle wave is considered to be the autocorrelation of the signal's sideband and used for CD monitoring. The CD up to 90 ps/nm is monitored for the RZ signal, and the effects of the polarization mode dispersion (PMD) and wavelength misalignment are also discussed and experimentally investigated. This scheme requires neither modification at transmitter nor complicated digital signal processing at receiver. Furthermore, it is operated in all-optical, and has the potential to be applied to the higher speed system with optical time division multiplexed (OTDM) technique.