Grating-based transmission bandpass filters using dispersion-matched mode conversion

Helical distributed feedback fiber Bragg gratings and rocking filters in a 3D printed preform-drawn fiber

Using induced UV attenuation across a twisted fiber asymmetric core drawn from a 3D printed preform, linear fiber Bragg gratings (FBGs) are produced on one side of the core. By removing the twist, a helical grating with a period matching the twist rate is produced. Balancing the rate with the polarization beat length in a form birefringent fiber allows the production of a combined rocking filter and FBG device with tunable properties. Direct observation of the fiber grating dispersion within the rocking filter rejection band is possible.

Asymmetric transmission and reflection spectra of FBG in single-multi-single mode fiber structure

We give a comprehensive theoretical analysis and simulation of a FBG in single-multi-single mode fiber structure (FBG-in-SMS), based on the coupled mode analysis and the mode interference analysis. This enables us to explain the experimental observations, its asymmetric transmission and reflection spectra with the similar temperature responses near the spectral range of Bragg wavelengths. The transmission spectrum shift during FBG written-in process is observed and discussed. The analysis results are useful in the design of the SMS structure based sensors and filters.

Fabrication of long-period fiber gratings by use of focused ion-beam irradiation

Long-period gratings have been made in nonphotosensitive optical fibers by irradiation of the core of a fiber with a focused beam of high-energy protons. The irradiated fibers exhibit relatively low loss, even before thermal annealing, and possess strongly wavelength-dependent transmission. The absence of a mask provides the opportunity to tailor the grating to a desired profile, and a variety of grating profiles were explored. The profile most resembling a sinusoid was found to produce the cleanest transmission spectra.