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Assembly clearance has a great influence on the performance of precision parts. Improper assembly clearance affects the working state and induces failure of parts. A method to analyze the assembly clearance of the precision spherical coupling parts by analyzing the points cloud was proposed. The least square center was used to find a rough center. Accurate center was searched near the least square center by the particle swarm optimization (PSO) algorithm based on the minimum zone method. Radical clearance and Z clearance of precision spherical coupling parts were calculated. Furthermore, the dynamic change of assembly clearance was also calculated by rotating the parts. The sphericity error evaluation results were improved obviously compared with other results. The accuracy of the evaluation results improved 4.51%∼28.97%.

Electro–optic modulator is a key component for on-chip optical signal processing. An electro–optic phase modulator based on multilayer graphene embedded in silicon nitride waveguide is demonstrated to fulfill low-power operation. Finite element method is adopted to investigate the interaction enhancement between the graphene flake and the optical mode. The impact of multilayer graphene on the performance of phase modulator is studied comprehensively. Simulation results show that the modulation efficiency improves with the increment of graphene layer number, as well as the modulation length. The 3-dB bandwidth of around 48 GHz is independent of graphene layer number and length. Compared to modulator with two- or four-layer graphene, the six-layer graphene/silicon nitride waveguide modulator can realize π phase shift at a low-power consumption of 14 fJ/bit when the modulation length is 240 μm.

We propose a novel and efficient multi-functional optical fiber sensor system based on a dense wavelength division multiplexer (DWDM). This system consists of an optical fiber temperature sensor, an optical fiber strain sensor, and a 48-channel DWDM. This system can monitor temperature and strain changes at the same time. The ranges of these two sensors are from −20 °C to 100 °C and from −1000 μ ε to 2000 μ ε , respectively. The sensitivities of the temperature sensor and strain sensor are 0.03572 nm/°C and 0.03808 nm/N, respectively. With the aid of a broadband source and spectrometer, different kinds and ranges of parameters in the environment can be monitored by using suitable sensors.

In precision glass molding (PGM) of glass materials with a high melting point, heat treatment of nickel phosphorus (Ni–P) should be made in advance to eliminate mold deformation during the high temperature molding. During the process, crystallization occurs on the plating and crystalline Ni–P with a particular micro-machinability is generated. Burrs of large sizes with a fibrous structure are observed on the microgroove ridge during the study of the fly cutting microgrooving. The Poisson burr accumulation in each material removal period is considered as the reason for the burr formation and a model of the burr accumulation in fly cutting is established based on the concept of maximum effective cutting thickness. According to the model, a high feed rate leads to the restriction of burr formation while fracture pits tend to be generated on the microgroove ridge. The fracture pits caused by the brittle removal of the material could be eliminated through the feed rate adjustment of fly cutting. The optimal processing parameter is proposed in consideration of the burr formation restriction and the elimination of fracture pits. The efficiency of microgroove mold machining is significantly improved. A high-quality microgroove mold is fabricated and the serviceability of the mold is tested through a PGM experiment.

A highly sensitive waveguide temperature sensor based on asymmetric Mach–Zehnder interferometer was designed and experimentally demonstrated. The interferometer is based on the polymer/silica hybrid waveguide structure, and Norland Optical Adhesive 73 (NOA 73) was employed as the waveguide core to enhance the temperature sensitivity. The influence of the different length differences between the two interferometer arms on the sensitivity of the sensor was systemically studied. It is shown that the maximum temperature sensitivity of −431 pm °C−1 can be obtained in the range of 25 °C−75 °C, while the length difference is 92 μm. Moreover, the temperature sensitivity contributions from different core materials were also investigated experimentally. It is shown that the waveguide material and microstructure of the device have significant influences on the sensitivity of the waveguide temperature sensor.

In this work, long-period waveguide grating-based tunable wavelength filters using organic–inorganic grafting poly(methyl methacrylate) (PMMA) materials are designed and fabricated by metal-cladding directly defined technique. The thermal stabilities and optical properties of the organic–inorganic grafting PMMA core materials are analyzed. Structures and performance parameters of the waveguide gratings and self-electrode heaters are designed and simulated. The contrast of the filter is about 15 dB and the resonant wavelength can be tuned by different electric powers applied to the metal-cladding self-electrode heaters. The temperature sensitivity is 3.5 nm/°C and the switching time is about 1 ms. The technique is very suitable for realizing the optoelectronic integrated wavelength-division-multiplexing systems.

Optical loss induced by the arbitrary structure discontinuity in the Au stripe that supports long-range surface plasmon-polaritons (LRSPPs) propagation is investigated in this paper. A broad range of arbitrary gap sizes, 4 to 20 μm, is reported for 25 nm thick Au stripe with different widths embedded in 5 μm thick optically symmetric polymer SU-8. The simulations and experimental data find a high tunneling efficiency of the long-range mode power transmission of larger than 50% over a 10 μm gap at a wavelength of 1550 nm. Accordingly, a thermally activated in-line Mach–Zehnder interferometer switch based on the guiding of LRSPPs along Au stripe with gaps is designed and fabricated. Switching characteristics are analyzed upon heating one arm of the interferometer through the passage of current therein. The fabricated switch exhibits an extinction ratio of 17 dB with a driving power of 13 mW. The results prove that LRSPPs are insensitive to technological imperfections and waveguide interruptions, which is of benefit to active plasmonic device applications.

A heat-induced multimode interference (MMI) variable optical attenuator at 1310 nm wavelength, based on novel organic?inorganic hybrid materials is successfully designed and fabricated. The thermal stability and optical properties of the sol?gel materials are analyzed. The thermo-optic (TO) coefficient of the organic?inorganic hybrid material is obtained as ?1.85???10?4 ?C?1. The characteristic parameters of the waveguides and heat-induced electrodes are carefully designed and simulated. The propagation loss of a 4 ?m-wide straight waveguide is 0.56 dB cm?1. The attenuation of the device is about ?25 dB, and the applied electric power is 36.2 mW. The new material system and low-cost fabrication technique could be suitable for realizing large-scale photonic integrated circuits.

A quasi-rectangular waveguide polymer Mach?Zehnder (M-Z) electro-optic (EO) modulator based on an organic/inorganic hybrid material with thermal bias control is fabricated and demonstrated. Linear bias for the modulator is obtained through thermo-optic effect. The optical output is adjusted by changing phase difference between the two arms of the M-Z interferometer. A power consumption of 16.1 mW for ? phase change is observed owing to the application of silica cladding. This approach is proved to be effective to suppress direct current drift in polymer EO modulators.