The Sensor Peripherals

Fig. 1 contains some picture witnessing the structure of the SPs. In Fig. 1 a), the front panel is depicted. It has one optical input and one optical output, and an Ethernet port to communicate with the internal microcontrollers for remote configuration of the SP. This link will need a very low throughput of few tens of kbit/s. The coax output to the antennas for transmission and reception in S and X band are on the rear panel, which is not shown in these pictures. Fig. 1 b) shows the lower plate inside the SP box: there are only electric and electronic components, such as power supplies, high-power amplifiers (HPAs) for the X and S band, as well as switches in the two bands, to switch between the SP TX and RX modes. In Fig. 1 c), the intermediate plate is shown, with its AWG for the distribution of the gate, of the radar waveform in the optical domain, and of the unmodulated modes from the MLL. Moreover, before amplification stages, there are the wide-band PD to convert the optical radar waveform coming from the photonic core to the RF domain before transmission, and the EOM to convert the received RF radar echoes to the optical domain, before sending it to the photonic core. The polarization controller is employed to align the polarization of the incoming unmodulated modes from the MLL in the PC with the EOM input, for power optimization. The upper plate is shown in Fig. 1 d), where the S-band and X-band amplifiers and filters for TX/RX operation are visible. There is also the board for control and communication with the photonic core. Finally, from Fig. 1 e), it is possible to see the large heat sink mounted under the lower plate for temperature stabilization of the power-hungry HPAs.

Fig. 1: a) Front panel of the sensor peripheral box; b) upper internal plate, where the O/E conversion to transmit the radar waveform at RF and the E/O conversion of the received echoes are operated; c) intermediate internal plate, with the X-band and S-band filters and amplifiers, and with the board dedicated to communication and control of the peripheral; d) lower internal plate, hosting the switches and HPAs in S and X band; e) side view of the intermediate and lower plates. AWG: Arrayed-Waveguide grating; BW: Bandwidth; PD: Photodiode; EOM: Electro-optical modulator; EDFAs: Er-doped fibre amplifiers.