## 4 Optical CAM Technology
### Experimental Demonstration of an Optical CAM Cell  
The architecture of the optical Binary CAM cell is schematically illustrated in Figure 5a, comprising the optical FF memory connected to an SOA-MZI XOR logic gate. The optical FF stores the data of the CAM cell, while the XOR logic gate is used for comparing the incoming search bit of the destination address with the stored bit of the prefix. As described previously, the FF is powered by two wavelengths, \(\lambda\)\(\mathrm{I}\) and \(\lambda\)\(\mathrm{2}\), which are emitted at its two outputs, respectively. In order to achieve a content Comparison operation, one of the two wavelengths, carrying the stored bit information, here \(\lambda\)\(\mathrm{I}\), is connected as the control signal to the SOA-MZI XOR gate, while the second control branch of the SOA-MZI is fed with the incoming search bit. The comparison result between the search bit and the FF-memory content is imprinted on a new wavelength, \(\lambda\)\(\mathrm{3}\), that is fed as a CW probe signal at the SOA-MZI gate and emerges at its S-output port, forming the final CAM cell output signal. When the two signals feature equal bit-pulses and a match occurs between them, the \(\lambda\)\(\mathrm{3}\)-CW emerges at the U port of the SOA-MZI and a bit pulse of logical \"0\" is thus obtained at the S-port and the CAM cell output. On the contrary, when the search bit does not match the FF memory content, a differential \(\pi\)-phase shift is obtained at the SOA-MZI, and the \(\lambda\)\(\mathrm{3}\)-CW signal emerges at the S-port and a pulse of logical \"1\" is obtained at the CAM cell output. Regarding the update of the CAM memory content, a Write operation has to be performed for the FF by launching \(\mathit{Set}/\mathit{Reset}\) pulses through the respective CAM cell optical ports, so as to change its logic state. The proposed optical CAM cell architecture was experimentally investigated for both operations, i.e., content Comparison and Write operation at 10 Gb/s, using the experimental setup shown in Figure 5b. For the Comparison operation, the red-highlighted area of the setup was used. A 10 GHz SG was used to drive a PPG that modulated a LiNbO\({}_{3}\) modulator, in order to produce the 10 Gb/s NRZ \(2^{7}\)\(-\) 1 PRBS signal at a \(\lambda\)\(\mathrm{4}\) = 1557.9 nm wavelength, forming the search signal that is transmitted to the SOA-MZI XOR gate as the control signal and thus emulating the external search-bit. The comparison result is imprinted at the \(\lambda\)\(\mathrm{3}\) = 1548 nm wavelength and the result is obtained at the respective SOA-MZI XOR output, after being filtered at a 0.6 nm 3 dB-bandwidth OBPF. For the Write operation, the blue-highlighted area of the setup was used. The 10 GHz SG was connected to a PPG, which then provided two 10 Gb/s NRZ data streams that modulated two LiNbO\({}_{3}\) modulators to generate the \(\mathit{Set}/\mathit{Reset}\) data steams at a 1558.7 nm wavelength. The logic state of the FF was recorded through the respective FFOut1/2 ports at \(\lambda\)\(\mathrm{I}\) and \(\lambda\)\(\mathrm{2}\), respectively, filtered by 0.6 nm 3 dB-bandwidth OBPFs centered at \(\lambda\)\(\mathrm{I}\) and \(\lambda\)\(\mathrm{2}\), which were then analyzed by an OSC and a BERT. EDFAs and VOAs were incorporated in both experimental setups for power loss compensation and power level management of the signals, while PCs were used to adjust the signal polarization states. The experimental results obtained in the optical CAM cell demonstration can be seen in Figure 6. Figure 6a-d show the time traces and the respective eye diagrams obtained during the Content Comparison operation. The FF was manually set each time to one of the two states and studied for both stored FF data-bit of logical \"0\" and logical \"1\", shown in Figure 6a.