Design of inductive p-i-n diode matching for optical receivers withincreased bit-rate operation

We have studied matching of a p-i-n photodiode (PD) with a single serial inductive element for broadband operation. The bit rate and rise time may be significantly improved, compared to a device without inductor for nonreturn-to-zero (NRZ) modulation. The matched device offers improved pulse equalization leading to increased receiver sensitivity, and reduces the need for an additional pulse-equalizing filter. The material is presented so that it can serve as a guideline of how the inductor can be included when choosing the thickness of the absorption layer and/or area for a p-i-n PD design, and ends with typical design examples     

Experimental and analytical evaluation of packaged 4×4InGaAsP/InP semiconductor optical amplifier gate switch matrices foroptical networks

Packaged 4×4 semiconductor optical amplifier gate switch arrays have been studied experimentally and analytically. Experimentally, a dynamic range of the input power to the switch of more than 20 dB was obtained at 622 Mb/s with less than 2 dB power penalty. Wavelength division multiplexing transmission with four channels at 622 Mb/s each through the same path was successfully demonstrated. The switch was also evaluated in an installed fiber network, where a 2.5 Gb/s signal was transmitted through three cascaded switch routes and 160 km fiber. A numerical time-domain model incorporating an electrical filter in the receiver confirmed the experimental results. It furthermore indicated that residual reflections between the different waveguide sections within the switch and at the chip facets may degrade the performance of the switch     

Comments on “Noise in an optical amplifier: formulation of anew semiclassical model”

The authors comment on the semiclassical model equations in a paper on semiconductor optical amplifier noise     

Laser linewidth broadening caused by a laser amplifier

It is shown that a laser amplifier connected to a laser will broaden the linewidth with a factor on the order of the laser multiplier power gain. The laser linewidth can be broadened in comparison to the free-running linewidth if the laser is connected to a laser amplifier because the noise emitted by the amplifier enters the laser and perturbs the oscillation. The broadening factor can be reduced to unity by inserting an isolator between the laser and the laser amplifier.<>     

Optical filter impact on eye opening in vestigial sideband systems

An analytical tool is presented in order to analyze and elucidate the impact of the optical filter position and steepness on eye opening in an optical vestigial sideband system with direct detection. It is shown that bit sequences containing solitarities (i.e., bit sequences containing single bits surrounded by several bits of opposite kind) are the major bit sequences to cause eye closure. In comparison with double-sideband modulation format, an eye opening penalty of 3-6 dB can be achieved with vestigial sideband format. The analytical tool helps to understand the interrelation between the bit sequence properties and the optical filter parameters.     

Representation of fatigue for wind turbine control

Fatigue is a critical factor in structures such as wind turbines exposed to harsh operating conditions, both in the design stage and in the control during their operation. In the present paper, the most recognized approaches to estimate the damage caused by fatigue in the component level are discussed and compared. The aim of this paper is to address the applicability of those fatigue damage estimation methods to control of wind turbines. Accordingly, for our discussion and comparison, we categorize fatigue estimation methods in a macroscopic scale as counting, spectral, stochastic and hysteresis operator methods. Copyright © 2016 John Wiley & Sons, Ltd.     

A cost-effective approach to introduce an optical WDM network inthe metropolitan environment

A case study shows that an optical wavelength division multiplexing (WDM) network can be employed in a metropolitan network in a cost effective way. In part, cost savings are realized due to the total number of line terminals required and the fact that the dimensions of the electrical nodes decrease when exploiting optical cross connects (OXCs) to a large extent. Optical WDM rings are also an important building element when designing a metropolitan network. A number of the properties of WDM rings are classified, resulting in eight different ring architectures. Additional requirements arise when considering ring-to-ring connections. The extent of the rings chosen for the case study is validated from the transmission point of view by a simple model. Finally, as an alternative to an all-optical approach, an opto-electrical approach is presented     

Parameter extraction from DFB lasers by means of a simpleexpression for the spontaneous emission spectrum

A simple expression for the amplified spontaneous emission from a laser biased below lasing threshold is applied to semiconductor laser parameter extraction. We demonstrate that accurate measurement of the coupling coefficient for distributed feedback (DFB) lasers with phaseshifts and end reflections is a practical possibility. It is also shown that the used expression, for a reciprocal device, can be derived directly from the wave equation using the Green's function     

Linewidth of an externally modulated laser subjected to Rayleighbackscattering from a fiber

It is found that the linewidth of a semiconductor laser that is externally phase modulated and connected to a fiber with Rayleigh backscattering is broadened. At low modulation rates the linewidth can be several orders of magnitude greater than the free-running linewidth, but it converges to the free-running linewidth at sufficiently high modulation rates. As a result, the isolation needed to attain a specific linewidth can be calculated