A temperature-insensitive 2-D inclinometer by incorporating two fiber Bragg gratings (FBGs) with a homogeneous pendulum transducer is proposed and experimentally demonstrated. The two FBGs are located in two orthogonal planes of the pendulum and only half of each FBG is glued on the surface of the columnar rod. Due to the strain difference between glued- and non-glued part of each FBG, the reflection spectrum of each FBG splits into two peaks. The direction and magnitude of inclination can be readily determined by measuring the wavelength separations of the split peak in two FBGs, whilst the temperature-induced cross-sensitivity is eliminated. A sensitivity of 0.047 nm/° with an accuracy of 0.23° is achieved within the tilt angle range of -20°–+20°.
An improved Brillouin-assisted photonic microwave downconverter that features simple structure and wide frequency tunable range is experimentally demonstrated. In order to obtain higher conversion efficiency, SBS-assisted notch filter is used to suppress the carrier of phase modulated signal. Due to the SBS-assisted notch-filtering is generated by the phase modulated signal itself, which simplify the system structure effectively. Furthermore, the effective suppression of the carrier of phase modulated signal and the diminishment of the second-order Stokes wave could be achieved simultaneously by optimizing the attenuation of the variable optical attenuator, which guarantee our scheme can operate over a wide frequency range.