Search

A real-time interrogation technology for a large-scale fiber laser sensor array is proposed and experimentally investigated by employing a hybrid topological structure based on the wavelength- and frequency-division multiplexing techniques. In this system, a 2-D n × m sensor array is established by using a 1 × n coupler and n 1 × m couplers. All sensors are divided into n units by the 1 × n coupler. In each unit, there are m fiber-ring laser sensors with approximately the same wavelength and different beat frequencies due to different laser cavity lengths. Meanwhile, different units are characteristic of different operating wavelengths by splicing different fiber Bragg grating (FBG) as a reflector. Therefore, each sensor has a unique wavelength- and frequency-encoded information. All sensors can be interrogated by the combination of wavelength and frequency multiplexing technology. In the paper, a 4 × 4 sensor array is set up experimentally to verify the interrogation ability, and the sensing information of the strain and temperature has been successfully extracted. The experimental results show that the proposed interrogation system has the ability of real-time monitoring for a large-scale fiber laser sensor array.

A novel lateral stress sensor based on a compact in-fiber Mach-Zehnder interferometer (MZI) and Fourier analysis is proposed and demonstrated. The in-fiber MZI is formed by cascading two offset splicing joints. The interference occurs between the copropagating fundamental core and cladding modes. The influence of offset value on the performance of modal interferometer, including the extinction ratio and insertion loss, has been experimentally investigated. The spatial spectra of the proposed in-fiber interferometers with different interference lengths are analyzed by Fourier transform. An in-fiber interferometer with an interference length of 30 mm has been fabricated for lateral stress measurement. The performance of the lateral stress sensor is investigated in a spatial frequency domain by Fourier transform of the corresponding transmission wavelength spectra. The responses of intensity peaks to different lateral stresses are analyzed in the spatial frequency domain. The sensitivity of the in-fiber MZI-based lateral stress sensor is as high as 0.00455/μm.The proposed lateral stress sensor possesses the advantages of simple and compact structure, high sensitivity, ease of manufacture, and low cost, and it will provide a simple and effective method for detecting the slight fiber deformation induced by lateral stress.

A new method to fabricate the multiwavelength DFB semiconductor laser array (MLA) is proposed for the first time based on sampled grating and s-bent waveguide. According to the detailed precision analysis, the lasing wavelength accuracy of the proposed structure is significantly improved. Because the common holography exposure and micrometer photolithography are used to fabricate the sampled grating and the bent waveguide in this method, the fabrication cost is very low. Therefore, it offers a suitable method for massive fabrication.