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We investigate the performance of a microfiber strain sensor based on the nonlinear four-wave mixing process. This simple sensor of only an elliptical microfiber has considerable advantages, such as sensing directly by microfiber inherent nonlinearity in the telecommunication range and being compatible with the existing fiber network. Dispersion, nonlinearity, and strain effect are analyzed to find optimum sensing performance. The numerical simulations reveal that the strain can cause a marked wavelength shift of the signal wave. The wavelength shift range can be more than 74 nm within a reasonable strain range. To the ultimate strain range of 30 \textm\varepsilon , the average strain sensitivity of 2.46 pm/ $\mu \varepsilon $ can be obtained when the pump wavelength is 1550 nm and the peak power is 100 W. In addition to the range of 5 \textm\varepsilon , it could achieve 9.86 pm/ $\mu \varepsilon $ by optimizing the fiber size and highly birefringent characteristic. This strain sensor with high sensitivity, simple configuration, light, and portable performance has wide applications in mechanical detection and fault diagnosis and is of intensified interest for a great deal of wavelength selected devices in quantum information process. [ABSTRACT FROM PUBLISHER]

We present a compact highly sensitive microfiber coupler-based twist sensor formed by fusing and tapering two optical fibers and then connecting two of the pigtails to form a Sagnac loop. The device is miniature, low cost, and easily fabricated. The sensor has high twist sensitivities of $\sim 0.9$ nm/° when measuring wavelength shift and $\sim 0.16$ dB/° when measuring transmission power, both of which confirm that the sensor has good potential for application in the structural health monitoring and other areas. [ABSTRACT FROM PUBLISHER]

Metallic grating (MG) with high accuracy is fabricated on the side surface of a D-shaped fiber by using focused ion beam (FIB) machining. The D-shaped fiber is obtained through polishing the cladding of a single-mode fiber away from one side. Then, a thin-film layer of gold is deposited on the flat side surface. A 38- \mu\m-long grating with the pitch of 485 nm is further milled on the gold film. The guiding mode and the surface plasmon polariton mode are thus coupled in the MG through the evanescent field for sensing applications. The refractive indexes of pure water and isopropanol are measured. A sensitivity of 917 nm/RIU is obtained. [ABSTRACT FROM PUBLISHER]

The dispersion characteristics of an optical nanowire microcoil resonator (ONMR) are investigated, which show remarkable influence on their performances at a high bitrate. In addition to the waveguide dispersion it was found that the adjacent ring coupling also has notable contribution to the total dispersion. If the nanowire diameter's range is from 1.5 to 5 μm, the waveguide dispersion and coupling dispersion could almost be canceled with each other so that the total dispersion is well suppressed, which is desired in high-speed (10 Gb/s and beyond) optical systems. On the other hand, both positive and negative dispersion could be obtained by adjusting suitable ONMR parameters. Even a tailored dispersion curve could be designed theoretically. These results are helpful for ONMR-based device design in communication and sensing applications. [ABSTRACT FROM PUBLISHER]

A liquid crystal tunable bidirectional isolator is proposed. A wave plate is employed to realize a wavelength interleaving function. If it works as a full wave plate, the corresponding light only may pass along a specific direction while the opposite way is isolated. However, for wavelengths that the light experiences a half wave plate, the isolator's passing direction is reversed. A liquid crystal cell is utilized to tune the isolator so that both the isolated wavelength and direction could be reconfigured. A 100-GHz channel-interleaved tunable bidirectional isolator is demonstrated with \sim \ 30 dB isolation in both directions. The spectral response at ITU grids are further flattened by using a wave plate stacking technique. [ABSTRACT FROM PUBLISHER]

We propose a possible approach to realize a highly birefringent slot microfiber by postprocessing a circular microfiber (CMF). The shape can be fabricated with very high repeatability, reliability, and accuracy. Light field can be enhanced and confined in the nanometer-wide low index slot, and the birefringence achieves as high as 4\times 10^-2. The slot-microfiber has the advantages both of a microfiber and a slot waveguide. It is perfect for miniature fiberized polarization manipulation devices and its unique geometry can also greatly enhance the refractive index sensitivity (nearly ten times higher than that of CMFs) for evanescent-field-based gas sensors. [ABSTRACT FROM PUBLISHER]