An erbium-doped fiber ring laser with embedded Mach–Zehnder interferometer (MZI) is constructed and experimentally demonstrated for strain and refractive index (RI) measurement. The MZI consists of a segment of thin-core fiber sandwiched between two single-mode fibers and acts as both the sensing component as well as a bandpass filter to select the lasing wavelength. The strain sensitivity of ∼-0.97 pm/μϵ and RI sensitivity of ∼44.88 nm/RIU are obtained in the range of 0 to 1750 μϵ and 1.3300 to 1.3537, respectively. The high-optical signal-to-noise ratio of >50 dB and narrow 3-dB bandwidth of <0.11 nm obtained indicate that the fiber ring laser sensor is promising for high-precision strain and RI measurement.
We demonstrate an optical Fabry–Perot interferometer fiber tip sensor based on a glass microsphere glued at the etched end of a multimode fiber. The fiber device is miniature and robust, with a convenient reflection mode of operation, a high temperature sensitivity of 202.6 pm/°C within the range from 5°C to 90°C, a good refractive index sensitivity of ∼119 nm/RIU within the range from 1.331 to 1.38, and a gas pressure sensitivity of 0.19 dB/MPa.
An optical fiber in-line Mach-Zehnder interferometer based on a fiber internal mirror constructed by use of a hollow ellipsoid fabricated by femtosecond laser micromachining and fusion splicing technique is demonstrated. The interface of the hollow ellipsoid surface and air can act as an internal mirror. The device has been used for refractive index, bending and high temperature measurement and simultaneous multiple parameter sensing.
We have carried out a detailed simulative study of the photonic band-gap crystal fiber sensor sensitivity by using the finite difference beam propagate method. The effect of the incident wavelength and the fill factor on the relative sensitivity of the sensors has been simulated. The simulative results show that with the incident wavelength and the fill factor increased, the relative sensitivity will be improved, the sensitivity of photonic band-gap crystal fiber sensor will be higher. The simulation results can provide the guidance for the further experimental study.
Differential Absorption Lidar for detecting atmospheric NO<sub>2</sub> (NO<sub>2</sub>-DIAL) is used extensively for its high precision and
spatial resolution, and the measurement can be done real-time with a wide range. The design of spectrum-dividing
system is a key component of lidar. According to characters of DIAL, such as adjacency of laser wavelength and
weakness of received signal, a set of optic fiber-grating spectrum-dividing system is developed. The system has the
advantages such as high spectral resolution, efficiently divide lidar echo signals in different wavelengths, weak
attenuation, receive and process signals in two channels synchronously, etc. So the SNR of receiving system has