UV-induced Gratings Research Articles

Hydrogen loading for fiber grating writing with a femtosecond laser and a phase mask.

The threshold for the fabrication of fiber Bragg gratings with ultrafast 800-nm radiation and a phase mask was studied in SMF-28 and all-silica core fiber by use of 125-fs pulses. High-pressure molecular hydrogen loading (H2 loading) was observed to significantly lower the grating writing threshold in standard Ge-doped telecommunication fiber. No reduction was observed with all-silica core fiber. The index change appeared to be confined to the Ge-doped core region of the fiber. Gratings in H2-loaded SMF-28 had thermal annealing behavior similar to UV-induced gratings. Unlike UV-induced H2-loaded gratings, no absorption associated with Ge-OH defect formation was observed.

Characterizations at very high temperature of electric arc-induced long-period fiber gratings

Electric arc-induced long-period fiber gratings, with low insertion loss (<0.2 dB) and high isolation peaks (−24 dB), have been fabricated in standard single-mode fiber (Corning SMF28). High temperature characterizations of the fabricated gratings in the range of 30 to 1200 °C have been performed. The sensitivity are in good agreement with recent published works. Specific spectral shift of the resonance peaks with temperature have been shown. Temperature annealing of the gratings, at 200, 400 and 600 °C show high thermal stability compared with UV-induced gratings. More particularly, modal dependence of the resonance shift and time dependence during annealing cycles, have been investigated at high temperature. The evolutions of the spectra have been related to the development of internal stresses in the fiber. These temperature characterizations help to explain the writing mechanism of these gratings.

Characterization and simulation of long period gratings fabricated using electric discharge

We report the characterization and theoretical simulation of long period gratings fabricated using electric arc discharge in two different fibers namely, SMF-28 ( Δ=0.0036) and DSF ( Δ=0.009). We show that this technique can efficiently fabricate gratings with required strength of coupling on both fiber types by choosing appropriate arc current and duration of the arc. We compare the transmission spectra of the fabricated gratings to the theoretically simulated plots and find the equivalent refractive index modulation created in the grating. Unlike the case of UV-induced gratings, the resonance wavelength in these gratings depends only on the period and is independent of the arc current that is controlled to achieve different refractive index modulations. Thus this technique enables easy and independent control of the fiber parameters.

Integrated-optical Mach–Zehnder add–drop filter fabricated by a single UV-induced grating exposure

A four-port bandpass filter is demonstrated with good performance by use of UV-induced Bragg gratings in P-doped channel waveguides without UV trimming. The simple, single-step fabrication procedure is experimentally and theoretically analyzed, and tolerances are calculated for achieving practical wavelength-division-multiplexed communication system performance.

Characterisation of dispersion properties in planarwaveguidesusing UV-induced Bragg gratings

UV-induced gratings have been employed to characterise dispersion properties and birefringence in buried phosphorus/germanium doped channel waveguides for different propagating modes. Bragg gratings with low index modulation and showing up to 50% reflectivity, have been written with 193 nm UV-light through a phasemask in waveguides with different dimensions.