## 2 Bloom Filter Labelling for Packet Switching with Photonic Integrated Switches
### Experimental Setup
Due to space limitations and the small pitch of the pads, the wire bonds from the phase shifters were in close proximity to the grating couplers, prohibiting in this way the use of a fiber-array for accessing simultaneously more than one input/output ports. Figure 4b depicts a photo of the packaged device, showing in more detail the very dense wiring connecting the MZIs to the PCB pads. Two electrical phase shifters (PS) are employed per interferometer, accounting for twelve in total. The electro-optical PSs of the MZIs are 1.25 mm long vertical PN diodes. Switching is realized by means of forward carrier injection so as to avoid the high V\({}_{\mathrm{pi}}\) requirements of the carrier depletion mechanism and to allow for the direct PS connection to the FPGA control ports without the intervention of amplifiers in the transmission line. Due to non-optimal fabrication process, the MZIs presented variation in the power required for setting in the BAR or CROSS state with the results presented in Table 1. The measurements reveal a V\({}_{\mathrm{\pi}}\) value for the six MZIs in the range of 0.9-1.1 V. The power consumption in the two extreme cases of having all phase shifters turned on and turned off are 115 mW and 5.6 mW, respectively. Due to imperfect p-n junction fabrication that resulted to almost 9 dB insertion losses for every p-n junction, the optical losses for the entire matrix were found to be in the range of 48-52 dB depending on the input-output port pair as it is shown in Figure 5.  
The cross-talk value of an individual MZI was measured to be in the range of 10 dB-18 dB. Moreover, the transfer function of the 4 \(\times\) 4 switch has been measured by injecting light in port#3, while switching to all output ports was realized via biasing the phase shifters from a DC source. Figure 4: (**a**) The 4 \(\times\) 4 Benes switch architecture depicting in bold the switches that were used in the 1 \(\times\) 4 programmable node demonstration; (**b**) Packaged SiP chip. Figure 5: Insertion Losses from any input to any output port for the 4 \(\times\) 4 Si photonics switch. The results have already been reported in [40], with crosstalk ranging from 8 dB to 12 dB for 1535 nm-1550 nm operation. The characterization of the switch in the time domain was performed by driving MZI#6 with RF signals, while the other MZIs were DC biased. The PN junctions were forward biased with two driving signals of 1 V\({}_{\text{P-p}}\) coming from a Pulse Pattern Generator (PPG) for push pull operation of the MZI. The PPG was running at 200 MHz with 50% duty cycle pulses. Figure 6 illustrates the recorded optical trace revealing a rise and fall times of 0.8 ns and 1.2 ns, respectively. In the case of the single-drive MZI operation, the respective response times were higher with a rising time of 2.5 ns and a fall time of 3 ns. For the Bloom Filter forwarding demonstration, the Si photonics switch chip was controlled by a Stratix V FPGA (Field Programmable Gate Array) board that provides up to 12.5 Gb/s control signals with a maximum peak voltage of with a 1.1 V. with a high and low level of 1.23 V and 0.15 V, respectively. The six MZIs were biased at the optimum operating point with an array of power supplies. The mixing of the RF and DC electrical signals was performed with six Bias-T devices that were connected to the SMA connectors leading to the upper phase shifter of each MZI. The electrical pulsed signal applied to the phase shifters had a peak power of \(\sim\)0.9 V that was marginally adequate for obtaining a pi phase shift. The DC bias was set for all MZIs at the operating point where the highest possible extinction ratio between the two output ports was observed. In the demonstrated scenario MZI#4, #5 and #6 out of the six were controlled by respective FPGA outputs, while MZI#2 was DC biased to perform at its OFF state.