Design and Control of Microwave Photonic Filters for Space Applications

With the ever expanding telecommunication networks, the Radio Frequency Interference (RFI) environment for weather satellites continually worsens. Mitigating this, outside new policies, can be achieved through precise and effective filtering of unwanted signals incident to these devices. However, traditional analogue RF filtering or digital filtering techniques suffer at the high mm-Wave frequencies that most of these devices operate at. Electromagnetic interference, increased losses, and distortion products make the traditional analogue RF filtering approach increasingly difficult. Therefore, a new form of filtering that can overcome these challenges is needed to begin to compensate for the increased RFI. This thesis proposes the use of microwave photonic filtering for this issue and demonstrates a widely tunable, dynamic, and narrow notch filter based on a nonlinear optical interaction called Stimulated Brillouin Scattering (SBS) in optical fibres. A mathematical model for
simulating the filter is given and compared with an experimental implementation that show good agreement in the performance. The proposed filter design shows a large tuning range between 2-26.5 GHz with a maximum 40 dB suppression that is tunable with a novel tuning method based on the state of polarisation of the light. The stability of the filter is also addressed, with a novel modulator bias control scheme being developed and tested experimentally. This research further develops the use of SBS filters in real world scenarios by expanding on the tunability of the filters and addressing some of the stability concerns. Such filters have a wide range of applications in satellites, aerospace, telecommunications, and beyond communication technologies. The bias control scheme developed also has
applications in these areas, as well as microwave photonics as a whole.