Network reliability is very important for the next generation of optical networks. In this paper, a highly reliable protection mechanism, which integrates the approaches of optical protection and microwave protection, is proposed for metro-access optical networks based on the wavelength division multiplexing (WDM) technique. By designing a scheme for the convergence of optical and wireless access and cooperating with designed remote nodes (RNs), not only can access for both wired and wireless service be provided simultaneously in each optical network unit (ONU) but also microwave protection can be realized when a failure occurs in a distribution segment. By developing a novel optical switch module (OSM) to cooperate with the dual-fiber ring structure, flexible switching can be achieved to protect against multiple types of failures in the feeder segment, including single-fiber faults, dual-fiber faults and multifiber faults. Based on the above structure, the influence of Rayleigh backscattering (RB) noise can be mitigated when the network is operating under all operating scenarios except for an inner-fiber fault. To further mitigate the influence of noise, optimization for upstream transmission performance is implemented by configuring a reflective semiconductor optical amplifier (RSOA). Furthermore, the feasibility of the overall scheme is verified through experiments and simulations under different operating conditions. The results show that the proposed mechanisms can achieve acceptable bit error rate performance and quality of service (QoS) metrics while also offering various advantages, including high reliability, large scale, and a relatively low cost.

In this paper, we verify the feasibility of our proposed design scheme for customizable optical pressure sensor based on the photo-elastic effect of SiO2 waveguide in asymmetric Mach-Zehnder interferometer (a-MZI) structure. The curve lengths and minimum radii of curvature of several common types of a-MZI arm curves are calculated theoretically. By analyzing the relationship between the radius of curvature of the long arm curve, the length of the long arm curve and the arm length difference of the a-MZI sensor under different types of arm curves, the design scheme for an a-MZI pressure sensor with a specific arm length difference is obtained. By selecting a rationalized arm design scheme, customization of the sensing range can be achieved. No special processing (such as etching) is required for the waveguide, which improves the pressure tolerance of the sensor. When using the SiO2 waveguide with a refractive index difference of 2%, the a-MZI pressure sensor based on sine type arm with arm length difference of 5 mm has a sensing range of 4.83 MPa and a sensitivity of 1.24 mW/MPa. The a-MZI pressure sensor with the ease of fabrication can be used to monitor various scenarios, such as marine and building monitoring.

This article proposes an integrated high-sensitivity temperature sensor based on SiO ₂ -asymmetric Mach–Zehnder interferometer (AMZI) and thermal-expansion-induced stress of aluminum-SiO ₂ . Mechanical analysis of this structure is carried out. The result shows that the SiO ₂ chip is compressed, and the waveguide length is decreased, leading to the central wavelength shift of the sensor. The sensitivity of the sensor can be customized by different arm lengths of the AMZI. The chip is fabricated using a standard planar lightwave circuit (PLC), and the aluminum alloy plate is glued to the chip using $\alpha $ -cyanaloc acrylic resin adhesive. The sensitivities of two sensors with different arm lengths are tested. The test results show the sensitivity reaches 6.86 and 54.2 nm $\cdot \text{K}^{-1}$ , respectively, which coincides with the theoretical analysis. With low cost and customizable sensitivity, this new device is applicable in many fields.