Masakazu Shigehara

Novel multichannel tunable chromatic dispersion compensator based on MEMS and diffraction grating

Using microelectromechanical systems and diffraction grating technologies, a novel tunable chromatic dispersion compensator for multichannel wavelength-division-multiplexing signals was developed. Independent channel-by-channel dispersion tuning with flat top loss spectra was experimentally confirmed.

Long-period fiber grating in a pure-silica-core fiber written by residual stress relaxation

Summary form only given. Long-period fiber gratings (LPFGs) have recently been attracting much attention for their possible applications such as gain-flattening filters for erbium-doped fiber amplifiers. Most LPFGs have been written in germanosilicate optical fibers because periodic structures can be easily obtained using UV-induced refractive-index changes due to the photosensitivity of Ge-related glass defects. This technique requires that fibers for LPFGs should contain photosensitive sites, and thus it cannot be applied to those which have no photoreaction centers inside such as pure-silica core optical fibers. Here we report the efficient fabrication of LPFGs in pure-silica-core optical fibers by residual stress relaxation. We also present the thermal dependence of the loss peak of the LPFG.

A four-channel multiwavelength fiber-grating external-cavity-laser array

A fiber-grating external-cavity-laser (FG-ECL) is expected as a useful light source in optical fiber communication systems. Its oscillation wavelength is determined by a reflection peak wavelength of the fiber grating. The wavelength controllability of fiber gratings is in the order of subnanometers, so the FG-ECL could be especially useful in dense wavelength-division multiplexing (WDM) systems where precise wavelength control of lasers is required. Utilizing a four-channel fiber grating array, we obtained a four-channel multiwavelength oscillation with 1-nm spacing, which demonstrated the feasibility of the FG-ECL as the WDM light source.

Novel multichannel tunable chromatic dispersion compensator based on MEMS & diffraction grating

Using MEMS and diffraction grating technologies, a novel tunable chromatic dispersion compensator for multichannel WDM signals was developed. Independent channel-by-channel dispersion tuning with flat top loss spectra was experimentally confirmed.

Optical fiber identification system using fiber Bragg gratings

Summary form only given. In this paper, we present a new identification method that uses identification-numbered (ID-numbered) fiber devices. The ID-numbered fiber devices consist of a combination of fiber Bragg gratings (FBGs) having various reflection wavelengths.

Improved erbium-doped fiber amplifiers employing chirped fiber gratings as ASE rejection filters for WDM transmission

Summary form only given. In summary, we have developed the chirped fiber grating optimisation as amplified spontaneous emission (ASE) rejection filters in Er-doped fiber amplifiers (EDFAs), and confirmed a significant improvement in the optical SNR in WDM transmission by simulations and experiments.

The novel design of a polarization independent multi-layer grating with high diffraction efficiency

To reduce polarization dependence in diffraction efficiency of first-order transmission gratings, we propose the novel design with multi-layer structure. High diffraction efficiency (>95%) and low polarization dependence (<2%) around C-band are obtained in our experiment.