A microfiber Fabry-Perot (FP) interferometer is proposed for photoacoustic sensing. It is fabricated by utilizing the 193-nm UV exposure and the phase mask technique. Two Fiber Bragg Gratings (FBG) which are formed in a microscaled optical fiber as a Fabry-Perot cavity serves as a sensor. In contrast to the conventional, new characteristics are attributed to the microfiber segment of the refractive index change. The microfiber FP interferometric photoacoustic sensor dependencies on acoustic pressure, temperature and refractive index are investigated. This compact photoacoustic sensor, with the diameter of microns, is suitable for photoacoustic imaging, especially in photoacoustic micro-tomography

As a typical active noise control algorithm, Filtered-x Least Mean Square (FxLMS) is widely used in the field of audio denoising. In this study, an audio denoising coprocessor based on Retrenched Injunction System Computer-V (RISC-V), a custom instruction set extension was designed and a software and hardware co-design was adopted; based on the traditional pure hardware implementation, the accelerator optimization design was carried out, and the accelerator was connected to the RISC-V core in the form of coprocessor. Meanwhile, the corresponding custom instructions were designed, the compiling environment was established, and the library function of coprocessor acceleration instructions was established by embedded inline assembly. Finally, the active noise control (ANC) system was built and tested based on Hbird E203-Core, and the test data were collected through an audio analyzer. The results showed that the audio denoising algorithm can be realized by combining a heterogeneous System on Chip (SoC) with a hardware accelerator, and the denoising effect was approximately 8 dB. The number of instructions consumed by testing custom instructions for specific operations was reduced by approximately 60%, and the operation acceleration effect was significant.