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An alternate solution to measure the stain and temperature simultaneously is proposed. In the acknowledged techniques, the most simple way of measuring stain and temperature simultaneously is to write fiber Bragg gratings (FBGs) in two fibers with different diameters. However, this way has a disadvantage of weak joint and high loss of splicing point which cannot be ignored. We present a new method to overcome this disadvantage by fabricating this dual-gratings sensing structure in one fiber, thus, the strength of this sensor is greatly increased and the transmission loss is nearly zero. This sensor is calibrated in a temperature range from 20 °C to 70 °C and in a strain range from 0 to 900 μɛ. The temperature sensitivity coefficients of these dual-gratings are completely consistent, and at the same time the strain sensitivity coefficients are flexible which can be adjusted by controlling the diameter of fiber. The reflection peak wavelengths of this sensor have a good linear relationship with strain and temperature and match the theoretical calculation well in our experiments.

We propose a novel method to map the optical frequency stability of the single-longitudinal-mode Er 3+ -doped fiber ring lasers with saturable absorber. This technology employs both the scanning FP spectroscopy and the unbalanced interferometer, providing a powerful tool to analyze the influence of dual-parameters on the stability state of lasers. The stability map versus the pump level and the cavity length is obtained, and five laser stability states appear sequentially when pump power increases. These regions were determined and some of their important characteristics were examined. We believe that our results will offer great benefits in optimization of this laser system.

A method to fabricate fiber Bragg grating (FBG) in an optical microfiber (OM) from a conventional photosensitive fiber is proposed in this letter. The cladding of a conventional photosensitive fiber is etched to 17 μm. The etched fiber is drawn to an OM 6 μm in diameter. The photosensitivity of the fabricated OM is effectively reserved. A FBG in the OM (MFBG) is successfully fabricated using a KrF excimer laser at a fluence of 400 mJ/cm2 through a phase mask with a pitch of 1 089.3 nm. The reflectivity of the FBG is approximately 10%, and the 3-dB spectrum bandwidth is 0.13 nm. The concentration of brine is measured by immersing the MFBG in the liquid, and the minimum detectable refractive index variation can reach 7.2 × 10-5 at a refractive index value of 1.33.

A novel numerical model of the dual-wavelength fiber ring lasers utilizing gain-equilibrium method is presented by developing the two level, homogeneous Giles model. To obtain the simulation method, the gain equilibrium condition is derived and modified to adapt to the iterative procedure in simulations. This condition is confirmed by both the numerical and experimental results, which indicate that the cavity losses of both wavelength channels play important roles in maintaining stable dual-wavelength emitting. The tolerant loss-bias is 0.05 dB in simulations and 0.4 dB in experiments, respectively. The difference between numerical and experimental results reveals that the inhomogeneous linewidth broadening of EDF contributes mostly to the improved power stability, but the loss vibrations play an important role in this effect.

Optic fiber polarizers and gratings are two widely used fiber components and in this paper we proposed an integrated fiber polarizing Bragg grating fabricated on SMF-28 fiber, which achieves reflecting and polarizing functions simultaneously. We established a composite multilayer grating waveguide model to demonstrate its principles. An integrated fiber polarizing Bragg grating was fabricated and the polarization properties of both the injected and reflected light were all measured, showing that this integrated fiber device can reflect light with a certain wavelength satisfying the Bragg condition as well as linearly polarize the reflected light. Long period monitoring results indicate that a stable performance of this integrated fiber polarized grating can be realized.

Fiber Bragg grating sensors have been attracted more attention due to its excellent advantages, such as small size, light weight, low cost, immunity to electromagnetic interference, multiplexing and so on, which offer a widely application in optical sensing and communication field. Following the appearance of micro/nano-fiber (MNF), it is imperative to develop the manufactured technology of MNF devices, MNF Bragg gratings are the important passive device among these. In this paper, we simulate the effective refractive index in fiber core using two-layer model. Meanwhile, we present a new method to fabricate a 6μm diameter fiber Bragg grating through successive improvement of manufactured technology. The small cladding diameter fiber was obtained by immersing an optical photosensitive fiber in different concentrations of hydrofluoric acid solutions. Then a MNF is fabricated from the small cladding diameter fiber by drawing. Finally a 6μm-diameter fiber Bragg grating was written using phase mask technology with a higher reflection. The testing results of this grating showed a good agreement with the simulation.

Optical fiber polarizer and grating are two widely used fiber components and in this paper we proposed an integrated polarizing grating fabricated in polarization-holding fiber, which achieves reflecting and polarizing functions simultaneously. A D-shaped multilayer grating waveguide model was established and the linearly polarizing principles in both reflection and transmission ports were presented. An integrated polarization-holding fiber polarizing grating was fabricated and the laser polarization states of incidence, reflection and transmission were all measured, showing that this integrated fiber device can achieve reflecting and polarizing functions simultaneously. The discrimination between the reflection and transmission was also investigated.

We have demonstrated that a polarization-insensitive anisotropic dynamic grating can be used to detect accident mode hopping in long-cavity-length fiber ring lasers. The polarization-insensitive property of the grating is realized by a Faraday rotator mirror and validated experimentally. The mode hopping properties of a particular single-longitudinalmode erbium-doped fiber ring laser is examined by an anisotropic grating with 3-m long erbium doped fiber. When mode hopping occurs, the grating responds a negative intensity peak. Repeated measurement shows that the continuing cavity length wandering during the laser operation is the origin of the accident mode hopping when there is no modulation applied to the cavity length.

Fiber Bragg grating hydrophones exhibit exceptional properties for acoustic detection, oil exploration and other applications have been induced widely attention following the maturity of fiber grating fabricate technology. As the basic key point of optical fiber hydrophone array, hydrophone design has been focused on by many countries over the past two decades. In this paper, we present a design of fiber Bragg hydrophone based on side-hole packaged to enhanced sensitivity and optimize its parameters through theoretical approach. In our theoretical analysis, the radial and axial strain induced grating length changes are taken into account. The results show that the material parameters such as Possion ratio and Young's modules and structural parameters like the position, diameter, ellipticity and number of the side-hole have significant effects on the sensitivity of the hydrophone. By optimizing these parameters, a high sensitivity can be achieved. This hydrophone is fabricated and experienced hydrostatic and dynamic sound pressure test. The experimental results are in good agreement with the theoretical results.

This paper presents comprehensive research on fused-tapered Bragg reflection integrative FGC where high-quality and easy-fabricating are two main considerations. The technical procedure of FGC fabrication is fixed after a series of experiments. The possible factors that may determine the device performance were carefully analyzed. The fused-tapered FGC was successfully fabricated and a novel testing system was established. The adding and dropping functions of FGC were investigated experimentally.

An integrated polarization maintaining fiber polarized Bragg grating is proposed, which achieves reflecting and polarizing functions simultaneously. This integrated polarized grating was designed to replace the traditional fiber polarizer and Bragg grating by a single fiber device, which may induce enormous performance promotion to optical fiber sys- tems incorporating the two devices, such as fiber ring laser, some fiber sensing networks, etc. An integrated fiber polarized grating was fabri- cated, and the polarization states of both the reflection and transmission were measured. The temperature and strain responses were also tested which indicated sufficient stability. The integrated fiber polarized grating was then applied to the fiber ring laser, and results indicated that a robust single-longitudinal and single-polarization mode laser can be realized by utilizing this design type of integrated polarized grating. © 2013 Society of

We propose a novel and practical method to exactly measure the transient reflectance spectra (TRS) of the adaptive filters based on dynamic population gratings. The modulating signals applied to the laser source play an important role. We specially designed a train of triangular amplitude modulated pulses with a small duty to modulate the laser frequency, and then the TRS was obtained from the grating responses to this pulse train. The measured half-zero-point bandwidths of the filter with and without 2.6 m cavity length are 20 and 60 MHz, respectively. Our research also indicates that the relatively high input power and a short cavity length may enhance the antiperturbation ability of lasers.