We introduce an optomechanical accelerometer for low-frequency acceleration detection and noise suppression, based on dual-heterodyne interference self-referencing testing. The accelerometer’s sensitive unit adopts a self-designed “dumbbell”-shaped mass-spring structure made of fused silica, with a theoretical natural frequency of 57.073 Hz. The two ends of the “dumbbell” structure form the reference interference optical system and the measurement interference optical system. Dielectric-coated high-reflectivity mirrors are attached to the structure’s ends. The accelerometer employs a dual-heterodyne interference self-referencing system and incorporates a reference interference optical system. This configuration serves to mitigate noise sources, including those originating from light sources and optical instruments, as well as environmental factors such as temperature and air pressure, improving the signal-to-noise ratio (SNR). Experimental results show that in air, the accelerometer has a noise-equivalent acceleration of 15 ng/√Hz, a 1.3-mg measurement range, and a 47-V/g scale factor. With its high SNR, small size, low cost, and simple setup, the accelerometer holds potential for aerospace, earthquake detection, and other applications.

Distributed acoustic sensing (DAS) based on a phase-sensitive optical time-domain reflectometer (Φ-OTDR) system has been widely investigated, but it is still limited by reliability and real-time issues due to signal fading and large amounts of data. A phase modulation scheme is applied to Φ-OTDR to generate sensing probes with multiple frequency components, using optimal modulation depth and frequency determined by analyzing the power ratios and correlations among these components. These signals propagate through the fiber with independent intensity fluctuations but carry the same external disturbance information. Synthesizing these signals effectively suppresses signal fading by reducing intensity fluctuations, leveraging the uncorrelated nature of fading across different components. Experimental results show that the minimum intensity of the synthesized signal is enhanced by 2.7 dB above the noise floor, and the signal fading probability is significantly reduced from 2.1577% to 0.0426%. To further enhance performance, a field-programmable gate array-based signal processing system is employed, achieving real-time DAS with high-precision phase demodulation within a 50-km range. The system is not only capable of recovering vibration signals of different frequencies in the laboratory environment but has also successfully completed vibration signal reduction experiments at several locations in the field. In addition, through the 4-day stability test, the system’s fading probability only fluctuates between 0.01% and 0.1%, and the daily average fading probability remains stable. These results fully validate the effectiveness of the proposed method in accurately recovering vibration disturbances.

To solve the repeatability deviations in optical spectrum analyzers (OSA) due to mechanical scanning errors and scan spacing variations during long-term measurements, we propose a real-time wavelength self-calibration method for OSA based on a Fabry-Perot etalon (F-P etalon). Different from traditional calibration methods that require all F-P reflection peaks, this method uses two high-reflectivity fiber Bragg gratings (FBGs) to filter the F-P spectrum, selecting only the two reflection peaks at one head and one tail of the C+L band to construct a reference spectrum. The reference spectrum is cascaded with the general FBG signal and transmitted through the OSA channel. The OSA is calibrated by monitoring changes in the reference spectrum during each scan and outputting the calibrated FBG wavelength value in real time through data processing, thereby achieving real-time wavelength self-calibration while maintaining stability during long-term measurements. The real-time wavelength self-calibration system was developed and tested over an extended period. The experimental results show that calibration reduced the maximum wavelength shift from 12.8 to 3.4 pm (26.5% of the original) and maintained stability over time, as well as reduced the shift dispersion from 2.38 to 0.75 pm (31.5% of the original). The calibration system significantly improved the long-term stability and measurement accuracy of the OSA. This research enhances the application of OSA in FBG sensors and shows promise for broader applications, including optical demodulation.

In the realm of visible light communication (VLC) systems, direct current-biased optical orthogonal frequency division multiplexing (DCO-OFDM) stands out as an advanced and potent multi-carrier modulation method. Nevertheless, a significant impediment in DCO-OFDM VLC systems is the elevated peak-to-average power ratio (PAPR). Selected mapping (SLM), a widely recognized approach, has been introduced as an effective solution to mitigate this issue; however, it entails considerable computational complexity. This paper introduces three methods: circularly shifted phase sequences (CSPSs), clustered circularly shifted phase sequences (CCSPS), and complemented clustered circularly shifted phase sequences that not only aim to reduce PAPR but also target the minimization of the computational burden. These methods generate phase sequence vectors exhibiting varying PAPR levels, enhancing their efficiency in producing lower PAPR sequences. Simulation outcomes demonstrate that the proposed techniques offer notable advantages in terms of computational complexity, albeit with a marginal increase in PAPR when compared with the conventional SLM scheme. Moreover, our methods maintain bit error rate integrity without necessitating the transmission of side information (SI), thereby streamlining system design. The elimination of SI transmission enhances the appeal of these techniques, rendering them highly advantageous for next-generation communication systems, where minimized complexity and maximized efficiency are paramount.

Transparent optoelectronic material and its waveguide structure play an indispensable role in integrated optical circuits. We study the characteristics of the Ce3+-doped phosphate glass including the transmittance and photoluminescence spectra. Then, it designs a planar waveguide on the Ce3+-doped phosphate glass and demonstrates the light propagation at a 632.8-nm wavelength in the structure. The preparation conditions for the waveguide are the 6.0-MeV O3+ implantation with a fluence of 5×1014 ions/cm2. The SRIM 2013 is used to simulate the irradiation process, obtaining information such as implantation depth, implanted-ion distribution, and energy loss. The prism coupling method and the end-face coupling technique are adopted to excite guided modes in the structure of the waveguide. The RCM is utilized to calculate the variation in refractive index caused by the irradiation. The mode field distribution and the geometric dimension make the Ce3+-doped phosphate glass waveguide suitable for multi-functional structures and systems.

We experimentally demonstrated a new parallel filter configuration based on a couple of Mach–Zehnder interferometers (MZIs) for reconfigurable multiwavelength Erbium-doped fiber laser (EDFL). The parallel filter comprises two arms fabricated by cascading two optical couplers (OCs). One arm is an in-line MZI (MZI-1) composed of a section of non-linear photonic crystal fiber (NLPCF) spliced between two single-mode fibers (SMFs), which can serve as a selector of the lasing wavelength in the proposed ring laser cavity. The other arm is an in-line MZI (MZI-2) constructed by a core-offset fusion splicing of a section of NLPCF between two SMFs, which can adjust the wavelength spacing of the multiwavelength laser. The free spectral range (FSR) is contingent upon the difference in the optical path between the two arms of the proposed filter structure. Consequently, employing the offset technology to splice the NLPCF allowed the regulation of the optical path difference between the two arms of the MZI. The two MZIs, arranged as parallel filters, were initially employed as transmission spectral filters for the concurrent generation of dual-wavelength in EDFL at 1530.6 and 1528.2 nm. Furthermore, the change in the spectra of the proposed filter via the adjustments of the polarization controllers (PCs) states was examined. Changing the PC1 state within the cavity alters the FSR of the parallel filter, enabling the attainment of switchable single, dual, and triple wavelengths. Subsequently, by altering the PC-2 integrated into the arm of the MZI-2, the FSR of the MZI-2 can be adjusted, thereby varying the wavelength interval from 1.0 to 3.0 nm. The results suggest that the proposed filter could be a promising approach for stable switchable and adjustable multiwavelength laser generation with potential applications in optical communications and sensing.