Paraxial designing of planar waveguide variable-index focusing elements: Part 1—lenses of circular symmetry

A paraxial ray equation is used to evaluate refractive index profiles for a family of radially symmetric planar waveguide lenses. Two cases are considered: the (theoretically) full-aperture solution, and the solution with smooth index variation (non-full-aperature case). In deriving the latter case a new method has been applied that consists of the proper choice of a continuous deflection function. Both types of index profiles are described by exceptionally simple formulas.     

Two-Frequency Brillouin Fiber Laser Based on Bragg Grating Fabry-Perot Cavity

Abstract

A novel and simple two-frequency Brillouin fiber laser is presented. It is based on a fiber Fabry-Perot cavity with fiber Bragg gratings as reflectors. The model of stimulated Brillouin scattering in fiber grating–based Fabry-Perot resonator is investigated. The laser allows conversion efficiency of close to 100% and suppresses the higher-order Stokes waves. The theoretical prediction is presented and the experimental demonstration is realized.     

Low-Loss Many-to-One Fiber Couplers with Few or Single-Moded Inputs and a Multi-Mode Output

The coupling of light from a number of few or single-moded fibers into a single multi-mode fiber is analyzed using geometric optics, and simple results demonstrating mode conservation are derived. Coupling from multiple single-mode fibers into a multi-mode fiber is investigated in detail using the overlap integral to determine coupling into each mode of the output fiber as a function of the light phase in the inputs. As well as results with practical relevance to fiber tapped delay-line filters and optical CDMA, the analysis provides pedagogic insight into light propagation and the light-gathering properties of fiber.     

Remote Temperature Sensor Based on the Up-Conversion Fluorescence Power Ratio of an Erbium-Doped Silica Fiber Pumped at 975 nm

Abstract

This article presents experimental results demonstrating the performance of an erbium-doped silica fiber as a remote temperature sensor in the interval from 20°C to 200°C. The sensor is based on the change in the fluorescence intensity ratio of two spectral bands as a function of temperature. The green fluorescence signal was generated by up-conversion processes in the erbium-doped fiber pumped at 975 nm. A radiometric analysis was applied to the erbium-doped fiber to evaluate its performance as a temperature sensor, and the results from this analysis were compared against other rare-earth-doped fiber sensors that utilize the intensity ratio technique.     

Asymmetrically Apodized Fiber Bragg Gratings for Applications in Dispersion-Less Fabry-Pérot Fiber Cavities

Abstract

This article presents a theoretical study of the dispersion properties of the asymmetrically apodized fiber Bragg gratings. It is shown that the dispersive behavior of these gratings may be changed from normal to anomalous, depending on the apodization function and the grating strength. The asymmetrical Bessel functions were chosen in order to demonstrate these properties of the gratings. The application of this effect in a dispersion-less Fabry-Pérot fiber cavity formed by two asymmetrically apodized fiber Bragg gratings is discussed.     

Dispersion Robustness of Millimeter Waves Generated by Up-Conversion Strategies

Abstract

The performance degradation caused by transmission along dispersive single-mode fibers of optically generated millimeter-wave signals using up-conversion is theoretically assessed and validated by numerical simulation. Up-conversion techniques based on optical double sideband, optical single sideband, and optical carrier suppression are considered. The generation of 60 GHz by frequency tripling using the optical single sideband is shown to be particularly tolerant to the fiber dispersion. The practical imbalance of Mach-Zehnder modulators is taken into account for optical carrier suppression modulation, where the finite extinction ratio is found to increase tolerance to fiber dispersion.     

Bidirectional Wavelength Reconfigurable Module Based on Tunable Fiber Bragg Grating and Remote Pump Amplifier

Abstract

This article presents a novel bidirectional wavelength reconfigurable optical network utilizing a remotely pumped erbium-doped fiber amplifier and tunable fiber Bragg gratings. The system is experimentally demonstrated at a 10-Gb/s per channel over 20-km fiber span that verifies the metro-network range system performance. The achieved power penalty is less than 1 dB when compared to the back-to-back transmission link. An example of practical application where the proposed module is used as an add/drop multiplexer and a remote node in the bidirectional wavelength division multiplexing passive optical network system is described.     

Multiple-Output Fiber-Ring Lasers and Amplifiers in a Hybrid CATV and ADSL Broadcasting Optical Fiber Communication System

In this article we propose two kinds of new fiber ring structure with a semiconductor optical amplifier. The first structure is a one-fiber-ring amplifier with an 8 × 8 fiber coupler and a semiconductor optical amplifier (SOA). The second fiber ring structure is a two-fiber-ring laser including an 8 × 8 fiber coupler, a 2 × 2 E/O modulator, and an SOA. The 14-output spectra of the fiber laser are measured. The gain coefficients of each port of the multiple-output-fiber-ring amplifiers are also measured. We apply these two kinds of fiber ring structures in a hybrid CATV and ADSL broadcasting optical fiber communication system. This application can develop a broadcasting system with large coverage area without using many laser diodes and optical amplifiers. The performance of such a system is also analyzed in this article.     

4 × 4 Plastic Optical Fiber Star Coupler Incorporated with a Common Polymer Waveguide Optical Power Distribution Region

Abstract

Two types of 4 × 4 plastic optical fiber star couplers incorporated with a polymer waveguide as the optical power distributor are proposed, and their high performances are demonstrated. The characteristics of the proposed star coupler are investigated based on ray optics, and its power distribution performance is evaluated in terms of the flatness of the coupling ratio and the amount of the excess loss. Under the best conditions, the flatness of the coupling ratio and the excess loss of the fabricated device have been obtained as 2.0 dB and 2.5 dB, respectively.