Experimental analysis of birefringence effects on fiber Bragg gratings induced by lateral compression

A tunable Bragg reflector based on a tapered three-dimensional (3D) hollow waveguide (HWG) with variable taper angle has been proposed and demonstrated. A large grating coupling coefficient for a large reflection band and a giant birefringence of 0.01 have been achieved by optimizing the structure of the 3D HWG. The large birefringence causes a delay difference between the orthogonal polarizations and the variable taper angle provides tuning in the delay difference. A 13 ps tuning in differential group delay has been reported with a 3 mm long compact device, which can be used for adjustable compensation of polarization mode dispersion in optical fiber links.

Giant birefringence and tunable differential group delay in Bragg reflector based on tapered three-dimensional hollow waveguide

A novel type of dual concentric core photonic crystal fiber (PCF) is proposed and theoretically analyzed, aiming at the design of tunable dispersive fiber elements for polarization-mode-dispersion (PMD) compensation. The adjustment of the fiber’s geometrical birefringence through the proper selection of structural parameters leads to very high values of differential group-delay (DGD). Moreover, the value of DGD can be dynamically tuned by infiltrating the outer core capillaries of the PCF with an optical liquid, which allows for the thermal control of its refractive index. Such fibers are envisaged as tunable dispersive fiber elements for PMD compensation or emulation modules.

Dual-core photonic crystal fibers for tunable polarization mode dispersion compensation

A novel resonant cavity enhanced (RCE) photodetector with flat-top and steep-edge response is presented. The response is obtained by designing a gradient-thickness P area in the absorption cavity. Simulation results show that the maximum and minimum values of the quantum efficiency in bandpass are 85.242% and 87.564% respectively, the ripple is about 3.6%, and 0.5 dB, 3 dB and 20 dB bandwidths are 0.3 nm, 0.4 nm and 1.2 nm, respectively. The mesa area is 10 μm × 10 μm and the frequency response bandwidth is 87 GHz. Compared with similar photodetectors, this photodetector has high quantum efficiency, narrow spectral response linewidth, good flat-top and steep-edge response and ideal high-speed characteristics.

A novel resonant cavity enhanced photodetector with flat-top and steep-edge response

Hollow waveguides are promising candidates for applications in sensing and high-power transmission. Flexible design and cost effective fabrication of hollow waveguides make it possible to realize integrated devices with small temperature dependence, tight control on optical confinement and tailorable characteristics. One of the potential applications of hollow waveguide is a tunable Bragg reflector, which can be used as building block for integrated photonics. In this review, integrated tunable Bragg reflector based on hollow-core optical waveguide is reviewed and presented; this Bragg reflector offers variable characteristics and design flexibility for applications in reconfigurable integrated photonic devices and circuits. Variety of tunable optical functions can be realized with on-chip Bragg reflector based on hollow waveguide, few of them are discussed in this review. Ultra-wide tuning in Bragg wavelength and on-chip polarization control can be realized using 3D hollow waveguide. A tapered 3D hollow waveguide Bragg reflector for an adjustable compensation of polarization mode dispersion (PMD) is then discussed. The utilization of a high-index contrast grating in hollow waveguide is demonstrated to reduce the polarization dependence and reflection-bandwidth. The polarization- and bandwidth control may be useful for realizing polarization insensitive devices and semiconductor lasers with ultra-wide tuning.

A hollow waveguide Bragg reflector: A tunable platform for integrated photonics

A novel tunable PMD compensation using linearly chirped fiber Bragg grating

We have fabricated the novel wavelength-selective photodetector with vertical taper structure. In this structure, wide tunable range, narrow spectral linewidth and high speed-response can be achieved simultaneously. The vertical taper, the key part in the whole integrated structure, was fabricated on Al/sub 0.3/Ga/sub 0.7/As epitaxial layer with inclined angle of 1.32/spl deg/ by dynamic mask etching technique. A spectral linewidth of 0.8 nm (FWHM) and a quantum efficiency of 75.17% have been achieved experimentally, with an absorption layer thickness of only 0.119 /spl mu/m. If we replaced the GaAs with InGaNAs as the absorption material, the spectral response of such a photodetector would easily extend to the long wavelength region.

Wavelength-selective photodetector with integrated vertical taper structure

The principle of dispersion compensation in transmission using uniform fiber Bragg gratings is described. Its compensation efficiency is analyzed numerically and the experimental results are reported. We broadened the pulse-width of the initial signals from 114.5 ps to 191.2 ps and 257.8 ps after 11.1 km and 22.2 km fiber transmission, respectively and then re-compressed them to 125.8 ps and 147.2 ps, respectively using one unchirped fiber grating with some tuning techniques.

Yuehui Xia

Papers

A novel tunable PMD compensation using linearly chirped fiber Bragg grating

Wavelength-selective photodetector with integrated vertical taper structure

Theoretical and experimental investigations of dispersion compensation based on transmission properties of unchirped fiber bragg gratings

Theoretical and experimental investigations of dispersion compensation based on transmission properties of uniform fiber Bragg gratings