Gain-controlled semiconductor optical preamplifier for the 100 Gbit/s 40 km ethernet receiver

A numerical investigation of the performance of an automatic gain-controlled semiconductor optical preamplified receiver for a 4×25¿Gbits/s wavelength division multiplexing transmission system with a 0–40 km reach is presented. We show that the control scheme acting on the semiconductor optical amplifier (SOA) gain increases the input power dynamic range of the optical receiver, thus allowing the transmission system to operate error free regardless of fiber length. In contrast, a fixed-gain optical receiver shows poor performance that is due to SOA nonlinearity and photodiode overload, which are well captured by the corresponding simulation models. The device represents a practical alternative to the next-generation high-speed Ethernet technology

Festkoerperlaser mit phasenkonjugierenden Spiegeln. Anlage zum Forschungsbericht - Fiberbuendel-Laser Abschlussbericht

1. Goals of the project - fiber-bundle-laser (FBL) with average power of 100 W, pulse energy 1-2 J, and simultaneous emission at two wavelengths - have been reached with optimization of the fiber material, the number of fibers, resonator and technology of the FBL. 2. Cultivation of highly doped multi component glasses for fiber laser applications. 3. Melting of the bundle end-sections by the 'glass-solder' method. 4. Additional results: passive Q-switching of the FBL, development of adapted micro-mirror arrays. 5. The possibility of scaling could be demonstrated and necessary conditions could be defined for the improvement of the beam quality (promising results with phase conjugation) and the total efficiency. (orig)SIGLEAvailable from TIB Hannover: DtF QN1(27,36) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Forschung und Technologie (BMFT), Bonn (Germany)DEGerman

GaN-based superluminescent diodes with long lifetime

We report on the reliability of GaN-based super-luminescent light emitting diodes (SLEDs) emitting at a wavelength of 405 nm. We show that the Mg doping level in the p-type layers has an impact on both the device electro-optical characteristics and their reliability. Optimized doping levels allow decreasing the operating voltage on single-mode devices from more than 6 V to less than 5 V for an injection current of 100 mA. Furthermore, maximum output powers as high as 350 mW (for an injection current of 500 mA) have been achieved in continuous-wave operation (CW) at room temperature. Modules with standard and optimized p-type layers were finally tested in terms of lifetime, at a constant output power of 10 mW, in CW operation and at a case temperature of 25 degrees C. The modules with non-optimized p-type doping showed a fast and remarkable increase in the drive current during the first hundreds of hours together with an increase of the device series resistance. No degradation of the electrical characteristics was observed over 2000 h on devices with optimized p-type layers. The estimated lifetime for those devices was longer than 5000 h

Broadband blue superluminescent light-emitting diodes based on GaN

We report on the achievement of III-nitride blue superluminescent light-emitting diodes on GaN substrates. The epitaxial structure includes an active region made of In0.12Ga0.88N quantum wells in a GaN/AlGaN waveguide. Superluminescence under cw operation is observed at room temperature for a current of 130 mA and a current density of 8 kA/cm(2). The central emission wavelength is 420 nm and the emission bandwidth is similar to 5 nm in the superluminescence regime. A peak optical output power of 100 mW is obtained at 630 mA under pulsed operation and an average power of 10 mW is achieved at a duty cycle of 20%