Efficient grating writing through fibre coating with femtosecond IR radiation and phase mask

Bragg gratings have been written through the polymer coating into hydrogen loaded SMF-28 fibres with ultrafast 800 nm radiation and a phase mask. Index modulations of up to 3.5times10^-4 were induced with fibre strengths remaining at ~85% of the pristine fibre value     

Excimer laser writing of submicrometre period fibre Bragg gratingsusing phase-shifting mask projection

Submicrometre period, first-order Bragg gratings have been written in optical fibre, for the first time to the authors knowledge, by projecting a phase-shifting mask. Gratings with a peak reflectivity of 85% at a Bragg wavelength of 1530 nm were recorded using single pulses from a broadband KrF excimer laser     

Fabrication and characterisation of long, narrowband fibre gratingsby phase mask scanning

Fibre Bragg gratings up to 50 mm in length have been fabricated using a phase mask scanning technique. Reflectivities of up to 70% and linewidths as narrow as 0.029 nm have been measured. The fabrication technique lends itself to writing gratings with controllable length, chirp and shading     

Dual wavelength fibre interferometer with wavelength selection via fibre Bragg grating elements

The use of intra-core fibre gratings to provide the selection of two stable, closely spaced wavelength-components at the output of a fibre interferometer is reported. An unambiguous sensing range in the optical path difference of an interferometer of +or-0.49 mm is demonstrated using two gratings spaced by 2.5 nm.<>     

Mode coupling in spiral fibre gratings

The coupling properties of spiral fibre gratings are presented. It is shown that LP₀₁ modes in spiral fibre gratings couple to both LP₁₁ even and odd modes     

Dual-wavelength cascaded Raman fibre laser

Dual-wavelength lasing at 1480 and 1500 nm has been demonstrated from a cascaded Raman fibre laser with a WDM coupler and two pairs of Bragg gratings. Intensity-adjustable, wavelength-tunable laser operation was achieved by tensile stress wavelength tuning of the gratings     

Matched photonic bandgap fibre and fibre Bragg grating dispersion for all-in-fibre stretch pulse amplification

Kilowatt peak power pulses with pulse durations of approximately 1.5 ps within 5% of transform limit using an all-fibre stretch pulse amplification system are demonstrated. Efficient high-quality stretch pulse amplification is achieved using a matched chirped fibre Bragg grating and low nonlinearity photonic-bandgap hollow-core fibre. The nearly ideal recompression highlights the robustness of ultra-short picosecond pulses to group delay ripple in chirped fibre gratings.     

Magnification of mask fabricated fibre Bragg gratings

Bragg gratings have been formed in optical fibres by diffraction of a phase mask. This technique is expanded by allowing for the possibility of shifting the Bragg wavelength for a fixed mask periodicity. This method uses a simple lens to introduce a curvature on to the wavefront of the diffracting light that results in a magnification of the original periodicity formed by the mask. The authors show experimentally that the Bragg wavelength is shifted to a shorter wavelength by the addition of a converging lens before the mask.<>     

Fabrication of chirped fibre gratings using etched tapers

A technique for fabricating fibre gratings with an accurately controlled chirp profile is demonstrated. The technique involves writing a grating over a section of fibre, the cladding of which has been tapered by etching it in HF acid. A strain gradient along the taper is used to produce the chirp either during or after writing. Linearly chirped gratings with bandwidths up to 4.8 nm have been demonstrated. Transmission filters have also been demonstrated when a step is made in the taper     

Differential phase tracking applied to Bragg gratings in multi-core fibre for high accuracy curvature measurement

High resolution quasi-static and dynamic curvature measurements are made by differential interferometric phase measurement of fibre Bragg gratings in separate cores of a multi-core fibre. A DC curvature stability of 1/spl times/10/sup -3/m/sup -1/ and an AC curvature resolution of 1/spl times/10/sup -4/ m/sup -1//Hz/sup 1/2/ are reported.     

High-temperature fibre Bragg grating thermometer

The use of gratings written in tin-doped silica fibres as a thermometer for high-temperature applications is described. Measurements up to ~800°C show a significant advantage over conventional fibre gratings. A considerable blue-shift has been observed at high temperatures. If corrections for blue-shift are taken into account, the errors are smaller than ~2°C     

Bend measurement using Bragg gratings in multicore fibre

The first measurements of curvature made using Bragg gratings written in separate cores of a multicore optical fibre are described. The gratings act as independent, but isothermal, strain gauges. The difference in Bragg wavelength between the gratings provides a temperature-independent measurement of the local curvature     

Single pulse Bragg gratings written during fibre drawing

For the first time the production of Bragg fibre gratings written by single excimer laser pulses as the fibre is being drawn is demonstrated. Reflectivities approaching 100% have been obtained, demonstrating the feasibility of online mass production.<>     

利用动态相位掩膜板法制作光纤光栅

在相位掩膜板法光纤Bragg光栅(FBG)制作系统中,通过高精度陶瓷压电(PZT)促动器对相位掩膜板进行运动控制,实现对光栅折射率交流调制量和相位的任意调制,从而实现相移、切趾和啁啾等FBG的制作,从而提高FBG制作工艺的灵活性。     

Optical comb filter based on spectral talbot effect in uniform fibre bragg gratings

A comb optical filter based on the spectral Talbot effect in uniform low reflecting fibre Bragg gratings is numerically and experimentally demonstrated, relaxing the need for any chirp or equivalent phase shifts between the gratings. It can be understood by the analogy between the compression and rate multiplication of phase modulated pulse trains and sampled fibre Bragg grating spectrum formation