Dual-pump Raman amplification with enhanced flatness using modulation instability

In this work, we utilize modulation instability to the broadening of the two CW-pumps of a wideband Raman amplifier. Applying nonlinear fiber process, we demonstrate a feasibility of a certain control over the broadening process, leading to clear improvements in the flatness of the amplifier gain over its operational bandwidth.

Semiconductor saturable absorber mirror passively Q-switched 2.97 μm fluoride fiber laser

A diode-cladding-pumped mid-infrared passively Q-switched Ho3+-doped fluoride fiber laser using a reverse designed broad band semiconductor saturable mirror (SESAM) was demonstrated. Nonlinear reflectivity of the SESAM was measured using an in-house Yb3+-doped mode-locked fiber laser at 1062 nm. Stable pulse train was produced at a slope efficient of 12.1% with respect to the launched pump power. Maximum pulse energy of 6.65 μ J with a pulse width of 1.68 μ s and signal-to-noise ratio (SNR) of ∼50 dB was achieved at a repetition rate of 47.6 kHz and center wavelength of 2.971 μ m. To the best of our knowledge, this is the first 3 μ m region SESAM-based Q-switched fiber laser with the highest average power and pulse energy, as well as the longest wavelength from mid-infrared passively Q-switched fluoride fiber lasers. © 2014 Astro Ltd.

An optical pump controlled tunable phase-shifted fiber grating transmission filter

Optical pump controlled, remotely tunable phase-shifted fiber grating transmission filters were analyzed. The transmission peak had a full width hail maximum (FWHM) bandwidth. With increasing control pump power, the resonant peak shifted towards the longer wavelength side. The efficiency of the system was largely affected by the greater number of sections of doped fiber as well as the absence of recirculation of unabsorbed pump beam. The configuration, besides its simplicity and cost-effectiveness, exhibited wavelength-independent pump-induced phase shifts and no anisotropic effects during operation.

Proton pump inhibitor prescribing following Endoscopic diagnosis in a district general hospital

Focal points: A systematic review of the use of proton pump inhibitors was conducted among patients undergoing diagnostic fibreoptic endoscopic examination of the upper gastrointestinal tract during the period July 2001 to February 2002 inclusive A total of 2,557 patients received a PPI following endoscopy and healing doses were prescribed to 75.3 per cent of these patients An “unknown indication” was stated as a diagnosis in 958 patients (37.5 per cent) of patients studied Although endoscopic diagnosis does not appear possible in all cases, the present study demonstrates that NICE guidance to employ the lowest appropriate dose of PPI is followed

Suppression of cladding-mode coupling loss in Bragg grating using standard single-mode fiber

We present a technique for suppressing cladding-mode coupling loss in fiber Bragg grating fabrication. Suppression of cladding-modes down to 0.2 dB in a Bragg grating of 18dB reflectivity has been achieved in hydrogen-loaded standard single-mode fiber.

Simple design method for gain-flattened three-pump Raman amplifiers

A simple and efficient approach to the optimal design of 3-wavelength backward-pumped Raman amplifiers is proposed. Gain flatness of 1.7 dB is demonstrated in a spectral range of 1520-1595 nm using only three pumps with wavelengths within the 1420-1480 nm interval.

Novel fiber Bragg grating sensor implemented in a polymer-core/silica- cladding hybrid optical fiber

A polymer-core/silica-cladding hybrid optical fiber is implemented by filling a capillary with UV-curable epoxy and a following UV-laser scanning exposure. A fiber Bragg grating is successfully inscribed in parallel using a phase mask. The experimental results show a reduced thermal response for the FBG and a theoretical analysis for such a hybrid optical fiber is performed which corroborates existing of a turning temperature for minimized thermal response. © 2014 SPIE.

A long period grating directional bend sensor incorporating index modification of the cladding

Long period gratings written into a standard optical fibre were modified by a femtosecond laser, which produced an asymmetric change to the cladding's refractive index resulting in a directional bend sensor.

High sensitivity biosensor based on dual-peak LPG sensitised by light cladding etching

We demonstrate a high sensitivity biosensor by fine tailoring mode dispersion and sensitivity of dual-peak LPGs using light-cladding-etching method. The etched device has been used to detect concentration of Hemoglobin protein in sugar solution, showing a sensitivity as high as 20nm/1%.

Low thermal sensitivity grating devices based on ex-45° tilting structure capable of forward-propagating cladding modes coupling

The authors describe a detailed investigation on tilted fiber Bragg grating (TFBG) structures with tilted angles exceeding 45°. In contrast to the backward mode coupling mechanism of Bragg gratings with normal and small tilting structures, the ex-45° TFBGs facilitate the light coupling to the forward-propagating cladding modes. The authors have also theoretically and experimentally examined the mode coupling transition of TFBGs with small, medium, and large tilt angles. In particular, experiments are conducted to investigate the spectra and far-field distribution, as well as temperature, strain, and refractive-index sensitivities of ex-45° devices. It has been revealed that these ex-45° gratings exhibit ultralow thermal sensitivity. As in-fiber devices, they may be superior to conventional Bragg and long-period gratings when the low thermal cross sensitivity is required. © 2006 IEEE.

The impact of pump phase-modulation and filtering on WDM signals in a fibre optical parametric amplifier

WDM signal degradation from pump phase-modulation in a one-pump 20dB net-gain fibre optical parametric amplifier is experimentally and numerically characterised for the first time using 10x59Gb/s QPSK signals.

Numerical and experimental analysis of sensitivity-enhanced RI sensor based on Ex-TFG in thin cladding fiber

We report a highly sensitive refractive index (RI) sensor in the aqueous solution, which is based on an 81°-tilted fiber grating structure inscribed into a thin cladding fiber with 40 μm cladding radius. The numerical analysis has indicated that the RI sensitivity of cladding resonance mode of the grating can be significantly enhanced with reducing cladding size. This has been proved by the experimental results as the RI sensitivities of TM and TE resonance peaks in the index region of 1.345 have been increased to 1180 nm/RIU and 1150 nm/RIU, respectively, from only 200 and 170 nm/RIU for the same grating structure inscribed in standard telecom fiber with 62.5-μm cladding radius. Although the temperature sensitivity has also increased, the change in temperature sensitivity is still insignificant in comparison with RI sensitivity enhancement.

Sensitivity enhanced SRI sensor based on an Ex-TFG in thin cladding fiber

A high sensitivity SRI sensor was fabricated by inscribing an ex-TFG in a thin cladding fiber, achieving enhanced SRI sensitivities of the TM and TE resonance peaks around 1180nm/RIU and 1150nm/RIU at the index of 1.345. © 2014 OSA.

Semiconductor saturable absorber mirror passively Q-switched 2.97 μm fluoride fiber laser

A diode-cladding-pumped mid-infrared passively Q-switched Ho 3+-doped fluoride fiber laser using a reverse designed broad band semiconductor saturable mirror (SESAM) was demonstrated. Nonlinear reflectivity of the SESAM was measured using an in-house Yb3+-doped mode-locked fiber laser at 1062 nm. Stable pulse train was produced at a slope efficient of 12.1% with respect to the launched pump power. Maximum pulse energy of 6.65 μJ with a pulse width of 1.68 μs and signal to noise ratio (SNR) of ~50 dB was achieved at a repetition rate of 47.6 kHz and center wavelength of 2.971 μm. To the best of our knowledge, this is the first 3 μm region SESAM based Q-switched fiber laser with the highest average power and pulse energy, as well as the longest wavelength from mid-infrared passively Q-switched fluoride fiber lasers. © 2014 SPIE.

Kerr nonlinear switching in a hybrid silicasilicon microspherical resonator

A hybrid silicon-core, silica-clad microspherical resonator has been fabricated from the semiconductor core fiber platform. Linear and nonlinear characterization of the resonator properties have shown it to exhibit advantageous properties associated with both materials, with the low loss cladding supporting high quality (Q) factor whispering gallery modes which can be tuned through the nonlinear response of the crystalline core. By exploiting the large wavelength shift associated with the Kerr nonlinearity, we have demonstrated all-optical modulation of a weak probe on the timescale of the femtosecond pump pulse. This novel geometry offers a route to ultra-low loss, high-Q silica-based resonators with enhanced functionality.