Plastic fiber design for THz generation through wavelength translation.

We report on an all-fiber terahertz (THz) radiation source by exploiting nonlinear parametric process in a theoretically designed microstructured-core double-clad plastic fiber (MC-DCPF). The required phase-matching condition is satisfied through suitable tailoring of the fiber dispersion and nonlinear properties at the pump wavelength of a high-power CO2 laser, with a CO laser of much lower power acting as a seed concomitantly. Our simulated results reveal that a THz radiation source at the frequency of ∼3 THz could be realized with a 3-dB phase-matching band width of 2.13 GHz in a 65-m-long optimized MC-DCPF. Maximum power conversion efficiency >1% is realizable even after including the material loss.

An efficient broad-band mid-wave IR fiber optic light source: design and performance simulation.

Design of a mid-wave IR (MWIR) broad-band fiber-based light source exploiting degenerate four-wave mixing (D-FWM) in a meter long suitably designed highly nonlinear (NL) chalcogenide microstructured optical fiber (MOF) is reported. This superior FWM bandwidth (BW) was obtained through precise tailoring of the fiber's dispersion profile so as to realize positive quartic dispersion at the pump wavelength. We consider an Erbium (Er(3+)) - doped continuous wave (CW) ZBLAN fiber laser emitting at 2.8 µm as the pump source with an average power of 5 W. Amplification factor as high as 25 dB is achievable in the 3 - 3.9 µm spectral range with average power conversion efficiency > 32%.

Design and realization of an all-fiber broadband tunable gain equalization filter for DWDM signals.

Design and fabrication of a tunable gain equalization filter for dense wavelength division multiplexed (DWDM) signals through erbium doped fiber amplifiers (EDFA) is reported. It is based on a side-polished fiber (SPF) half-coupler block loaded with a displaceable tapered multimode overlay waveguide (MMOW). A simple and accurate normal mode analysis is employed to design this filtering device for its subsequent realization. Equalization of a typical EDFA gain spectrum in the C-band within +/-0.35 dB or even less in the presence of various ITU standard C-band DWDM signal channels is demonstrated under varied operating conditions like add/drop of signals. Tunability of the filter notch is achieved through displacement of the SPF relative to the MMOW.

Refractometers and tunable components based on side-polished fibers with multimode overlay waveguides: role of the superstrate.

A normal mode analysis is applied to the investigation of the role of the superstrate in terms of its refractive index and thickness in estimating the performance of fiber refractometers and the tunability of fiber components based on evanescent coupling of a side-polished fiber to a multimode overlay waveguide. The model is shown to yield a complete transfer function and information about all the major characteristics of such in-line fiber devices. The results closely match the trends of the reported experiments.