The Rotational Shearing Interforometer has been proposed for direct detection of extra-solar planets. This interferometer cancels the star radiation using destructive interference. However, the resulting signal is too small (few photons/s for each m²). We propose a novel method to enhance the signal magnitude by means of the star–planet interference when the star radiation is not cancelled. We use interferograms computationally simulated to confirm the viability of the technique.

In this work, we study a double-sense twisted low-birefringence Sagnac loop structure as a sound/vibration sensing device. We study the relation between the adjustments of a wave retarder inside the loop (which allows controlling the transmission characteristic to deliver 10, 100, and 300 $\mathsf{\mu }\mathrm{W}$ average power at the output of the system) and the response of the Sagnac sensor to vibration frequencies ranging from 0 to 22 kHz. For a 300 m loop Sagnac, two sets of experiments were carried out, playing at the same time all the sound frequencies mixed for ∼1 s, and playing a sweep of frequencies for 30 s. In both cases, the time- and frequency-domain transmission amplitudes are larger for an average power of 10 $\mathsf{\mu }\mathrm{W}$, and smaller for an average power of 300 $\mathsf{\mu }\mathrm{W}$. For mixed frequencies, the Fourier analysis shows that the Sagnac response is larger for low frequencies (from 0 to ∼5 kHz) than for high frequencies (from ∼5 kHz to ∼22 kHz). For a sweep of frequencies, the results reveal that the interferometer perceives all frequencies. However, beyond ∼2.5 kHz, harmonics are present each ∼50 Hz, revealing that some resonances are present. The results about the influence of the power transmission through the polarizer and power emission of laser diode (LD) on the Sagnac interferometer response at high frequencies reveal that our system is robust, and the results are highly reproducible, and harmonics do not depend on the state of polarization at the input of the Sagnac interferometer. Furthermore, increasing the LD output power from 5 mW to 67.5 mW allows us to eliminate noisy signals at the system output. in our setup, the minimum sound level detected was 56 dB. On the other hand, the experimental results of a 10 m loop OFSI reveal that the response at low frequencies (1.5 kHz to 5 kHz) is minor compared with the 300 m loop OFSI. However, the response at high frequencies is low but still enables the detection of these frequencies, yielding the possibility of tuning the response of the vibration sensor by varying the length of the Sagnac loop.

We propose a spectral filter based on a plastic optical fiber with micro-holes as a low-cost, robust, and highly reproducible spectral filter. The spectral filter is explored for two configurations: a fiber extended in a straight line and a fiber optic loop mirror scheme configuration. The transmission traces indicate a spectral blue shift in peak transmission, at 587 nm, 567 nm, 556 nm, and 536 nm for zero, one, two, and three holes in the fiber, respectively. The filter exhibits a bandpass period of approximately 120 nm. Additionally, we conduct a comparison of the transmission with holes separated by distances of 1 cm and 500 μm. The results demonstrate that the distance between holes does not alter the spectral transmission of the filter. In the case of the fiber loop mirror configuration, we observe that the bandpass can be adjusted, suggesting the presence of multimode interference. Exploring variations in the refractive index within the holes by filling them with glucose solutions at various concentrations, we determine that the filtering band and spectral shape remain unaltered, ensuring the stable and robust operation of our spectral filter.

We propose a spectral filter based on Plastic Optical Fiber with micro-holes as a low-cost, robust, and highly reproducible spectral filter. The spectral filter is explored for two configurations: fiber extended in a straight line, and a fiber optic loop mirror scheme configuration. The transmission traces indicate a spectral blue shift of peak transmission, at 587 nm, 567 nm, 556 nm, and 536 nm for 0, 1, 2, and 3 holes in the fiber, respectively. The filter exhibits a bandpass period of approximately 120 nm. Additionally, we conducted a comparison of the transmission with holes separated by distances of 1 cm and 500 μm. The results demonstrate that the distance between holes does not alter the spectral transmission of the filter. In the case of the fiber loop mirror configuration, we observed that the bandpass can be adjusted, suggesting the presence of multimode interference. Exploring variations in the refractive index within the holes by filling them with glucose solutions at various concentrations, we determined that the filtering band and spectral shape remains unaltered, ensuring a stable and robust operation of our spectral filter.

Optical profilometry based on heterodyne interferometry was used to characterize the lateral surface topography of reflective surfaces with microstructures. A 633 nm laser beam is split into an unshifted object beam and a reference beam that is frequency-shifted by 80 MHz using a traveling-wave acousto-optic modulator. The object beam is focused onto the sample through a 100× microscope objective, recombined with the reference beam, and detected using a photodetector with a bandwidth of 150 MHz. At each scan position, a Universal Software Radio Peripheral (USRP) acquires the beat signal, and Fourier analysis isolates the heterodyne component. Electrical tests verified the recovery of a prescribed low-amplitude modulation, whereas translation of a plane mirror through focus identified a monotonic region for displacement-sensitive operation. Reflective silicon microstructures and a nominal 300 lines mm${}^{-1}$ grating were examined. The reconstructed maps reproduced the principal lateral features observed by scanning electron microscopy (SEM). For the grating-period comparison, the SEM-derived mean was 3.545 $\mathsf{\mu }$m, whereas the heterodyne reconstruction yielded a representative period of approximately 3.50 $\mathsf{\mu }$m, corresponding to an absolute difference of approximately 0.045 $\mathsf{\mu }$m (1.3%). The present experiments establish Fourier-domain signal recovery and lateral morphological characterization. Because a traceable axial calibration and an uncertainty budget were not available, the reconstructed vertical coordinate remains qualitative, and the results do not yet establish quantitative surface-roughness parameters.