Fiber Bragg grating inscription in four core fibers and their sensing applications

We inscribe FBGs in all cores of four core fiber simultaneously and investigate their thermal, strain and bending (both direction and magnitude) responses. The influence of fiber core distance on bending sensitivity is also discussed. © 2015 OSA.

Two-channel fiber Bragg grating fabricated by femtosecond laser and its application in switchable dual-wavelength erbium-doped fiber laser

Two-channel fiber Bragg grating (TC-FBG) consisting of two localized sub-gratings parallel in the fiber core is fabricated by femtosecond laser. Utilizing the fabricated TC-FBG, stable and switchable dual-wavelength erbium-doped fiber laser at room temperature is demonstrated. © 2015 OSA.

Highly efficient spectrally encoded imaging using a 45° tilted fiber grating

A novel highly efficient, fiber-compatible spectrally encoded imaging (SEI) system using a 45° tilted fiber grating (TFG) is proposed and experimentally demonstrated for the first time, to the best of our knowledge. The TFG serves as an in-fiber lateral diffraction element, eliminating the need for bulky and lossy free-space diffraction gratings in conventional SEI systems. Under proper polarization control, due to the strong tilted reflection, the 45° TFG offers a diffraction efficiency as high as 93.5%. Our new design significantly reduces the volume of the SEI system and improves energy efficiency and system stability. As a proof-ofprinciple experiment, spectrally encoded imaging of a customer-designed sample (9.6 mm x 3.0 mm) using the TFG-based system is demonstrated. The lateral resolution of the SEI system is measured to be 42 μm in our experiment.

2nd order Bragg rasonance generated in a 45° tilted fiber grating and its application in a fiber laser

We report the generation of a 13dB 2nd order Bragg resonance in a conventionally UV inscribed 45° tilted fiber grating, showing strong polarization dependency and its application for singe polarization output of a fiber laser. © 2010 Optical Society of America.

High spatial and temporal resolution interrogation of fully distributed chirped fiber Bragg grating sensors

A novel interrogation technique for fully distributed linearly chirped fiber Bragg grating (LCFBG) strain sensors with simultaneous high temporal and spatial resolution based on optical time-stretch frequency-domain reflectometry (OTS-FDR) is proposed and experimentally demonstrated. LCFBGs is a promising candidate for fully distributed sensors thanks to its longer grating length and broader reflection bandwidth compared to normal uniform FBGs. In the proposed system, two identical LCFBGs are employed in a Michelson interferometer setup with one grating serving as the reference grating whereas the other serving as the sensing element. Broadband spectral interferogram is formed and the strain information is encoded into the wavelength-dependent free spectral range (FSR). Ultrafast interrogation is achieved based on dispersion-induced time stretch such that the target spectral interferogram is mapped to a temporal interference waveform that can be captured in real-Time using a single-pixel photodector. The distributed strain along the sensing grating can be reconstructed from the instantaneous RF frequency of the captured waveform. High-spatial resolution is also obtained due to high-speed data acquisition. In a proof-of-concept experiment, ultrafast real-Time interrogation of fully-distributed grating sensors with various strain distributions is experimentally demonstrated. An ultrarapid measurement speed of 50 MHz with a high spatial resolution of 31.5 μm over a gauge length of 25 mm and a strain resolution of 9.1 μϵ have been achieved.

A fiber-compatible spectrally encoded imaging system using a 45° tilted fiber grating

We propose and demonstrate, for the first time to our best knowledge, the use of a 45° tilted fiber grating (TFG) as an infiber lateral diffraction element in an efficient and fiber-compatible spectrally encoded imaging (SEI) system. Under proper polarization control, the TFG has significantly enhanced diffraction efficiency (93.5%) due to strong tilted reflection. Our conceptually new fiber-topics-based design eliminates the need for bulky and lossy free-space diffraction gratings, significantly reduces the volume and cost of the imaging system, improves energy efficiency, and increases system stability. As a proof-of-principle experiment, we use the proposed system to perform an one dimensional (1D) line scan imaging of a customer-designed three-slot sample and the results show that the constructed image matches well with the actual sample. The angular dispersion of the 45° TFG is measured to be 0.054°/nm and the lateral resolution of the SEI system is measured to be 28 μm in our experiment.