# Fast Reconfigurable SOA-Based Wavelength Conversion of Advanced Modulation Format Data +
In addition, FWM is transparent to the different modulation formats where the information can be encoded in the amplitude, phase, and polarization of the optical carrier [14], and is also transparent to the signal baud rate (the wavelength conversion of the on-off keying (OOK) signal at 100 Gbaud having been demonstrated in [15]). Recently, a lot of work has been done on the wavelength conversion of data signals employing different modulated formats including (Differential) QPSK, 8-Phase Shift Keying (PSK), 16-QAM, and 64-QAM based on FWM in SOAs using single pump and dual pump wavelength conversion systems [16; 17; 18; 19; 20; 21; 22; 23; 24; 25; 26; 27]. In-addition to phase and amplitude, optical communication networks are employing polarization multiplexed (Pol-Mux) modulation formats to achieve twice the spectral efficiency by encoding data on two orthogonal polarizations of the light. When data is present in two orthogonal polarizations, it is very important to ensure that FWM-based wavelength converters are transparent to Pol-Mux modulation formats. Vector theory of FWM in nonlinear media is well understood and utilized for achieving polarization-insensitive wavelength conversion [28]. Vector theory was studied and verified in nonlinear SOAs and this was utilized to design a polarization-insensitive wavelength conversion scheme for Pol-Mux modulation formats utilizing dual co-polarized pumps in our earlier work [29]. Utilizing the understanding from these phase noise and polarization studies, we designed the most efficient and impairment-free wavelength converter based on FWM. We use this design to study the dynamic characteristics of the FWM-based wavelength converter and present the results, when the data is communicated in bursts/packets. One important issue that needs to be considered when using FWM for all-optical wavelength conversion of data signals, where the information is encoded onto the phase of the optical carrier, is the phase noise transfer issue between the pump and the converted idler. In [30], a simple relationship between the linewidth of the signal, pump, and converted idler in the FWM process was found by theoretical analysis and verified experimentally. For the case of the single pump FWM scheme shown in Figure 1a, the linewidth of the converted idler is the linewidth of the signal plus four times pump linewidth, and for the case of the dual pump FWM scheme shown in Figure 1b, the linewidth of the converted idler is equal to the summed linewidths of the signal and the dual pumps. The phase noise transfer problem will cause a significant effect for the FWM-based wavelength conversion of data with phase encoding, as it becomes more difficult to recover the data with the induced uncertainty in the phase of the wavelength converted idler. Thus, the linewidth is an important parameter for the pump laser to be employed in the FWM-based wavelength conversion system. An example of a typical all-optical packet-switched network which employs wavelength conversion is illustrated in Figure 1c. IP packets enter the network through the edge router where they are retransmitted on a new wavelength to avoid contention [31]. By employing the all-optical wavelength converter in this network, it can enable rapid routing of the same wavelength channels from any direction to any direction, and easily avoid the contention in which different packets with the same wavelengths are trying to leave the edge router. The wavelength converter consists of fast tuning tunable lasers as the pumps, an SOA, and a tunable optical filter. The wavelength of the wavelength-converted signal through FWM can be precisely altered by tuning the wavelength of the pump sources, and after the nonlinear wavelength conversion process in the SOA, the converted signal is then filtered out by using a tunable optical filter and sent to the next network node.