Ole Lumholt

Optimal design of single-cladded dispersion-compensating optical fibers

Specific and simple design relations are presented for different classes of single-cladded optical fibers designed to obtain maximum dispersion compensation. The performance limitations of the different fibers are compared, and the needs for very high refractive-index differences are evaluated.

Fundamental design of a distributed erbium-doped fiber amplifier for long-distance transmission

Comprehensive theoretical analysis on the design of a distributed erbium-doped fiber amplifier for long-distance transmission has been carried out, using a highly accurate model. The dispersion of the optical fiber as a function of the numerical aperture and the cutoff wavelength is included. Designs based on a bidirectional pumping scheme are evaluated, taking nonlinearities into account. The optimum value of the numerical aperture will be evaluated for cutoff wavelengths where the propagating pump power is single moded. For distances between each pumping station in the region between 10 and 100 km, the optimum ratio of copropagating and counterpropagating pump power will also be evaluated. >

Simple fiber-optic low-temperature sensor that uses microbending loss

A simple fiber-optic temperature sensor is constructed that uses the temperature dependence of microbending loss. The sensor is tested and shows high sensitivity and a strict linear scale over a wide range from 20 to 180 K. It is shown that a proper choice of signal wavelength can be used either to make the sensor more sensitive or to make it independent of changes in laser wavelength.

Numerical modeling of an integrated erbium-doped glass laser

Abstract An effective method for determining the laser wavelength, pump-power threshold, and slope efficiency of an integrated erbium-doped glass laser with step index profile is presented. Calculations based on this method show good agreement with experimental results published in the literature. Optimization of the laser wave-guide was also performed.

Optimum placement of filters in 1300 nm Nd-fibre amplifiers

Abstract A general procedure for determining the optimum placement of filters in Nd 3+ -doped ZBLANP fibres is presented. Extra gain of 5 dB per filter is predicted for the first four filters, yielding 20 dB of gain with 125 mW of pump power using three filters.

Gain variations for an erbium doped fiber amplifier in a temperature-range from 45 K to 320 K

The erbium doped fiber amplifier (EDFA) has emerged as a key element for long distance optical communication systems because of high gain, low noise, polarization insensitivity and low coupling losses. The temperature dependent gain of the amplifier in a small range around room temperatures is interesting for practical applications of the EDFA under normal operation [1,2]. Knowledge about the temperature dependence in a large temperature range is important for the basic understanding of the erbium ion and may yield to new applications for the Er-doped fiber. Earlier reports have shown gain variations, measured in a temperature range from approximately 233 Κ to 358 Κ for the pump wavelengths at 0.98 μπι [1] and 1.48μπι [2]. Gain measurements at cryogenic temperatures have been presented at the boiling point of liquid nitrogen (77 K), when pumped at 0.514 μπι [3], 0.8 μπι [4] and 1.48 μπι [5]. The results show an increased gain at this particular temperature compared to the gain around room temperature. This letter reports continuous gain measurements in a large range from 45 K to 320 K, showing that the gain dependence on the temperature is divided in four different linear sections, with significantly different gain to temperature coefficients in dB/K.

Demand for accuracy of the attenuation constant in distributed active fibers

Design of a distributed Erbium doped fiber amplifier for a long distance transmission line is investigated, using a very accurate model. The design is evaluated for a bidirectional pumping scheme, taking nonlinearities into account. Bit error rates based on amplified spontaneous emission are calculated. For distances between each pumping station equal to 100km, bit error rates lower than 10-10 at 4GBit/s is found.

Noise optimization of an Er-doped superfluorescent fiber source

A theoretical analysis of the noise properties of an Er-doped superfluorescent fiber source is presented. The optimum fiber design with respect to the signal-to-noise ratio and output power is found.

Optimum Design of Erbium-Doped Silica Waveguides

Erbium doped integrated optical planar waveguide amplifiers in silica on Si have received an extensive attention since the first report on amplification was presented last year [1]. This work by Kitagawa et al, showing 13.7 dB gain in a 19.4 cm long channel waveguide, is still the most significant result presented so far though also other laboratories now have fabricated Er-doped components on Si [2,3,4]. The ultimate goal however, is a few cm long high gain amplifier. The required extremely high Er-concentrations in such components, break the assumption that Er can be treated as isolated ions. Quenching through energy transfer between closely located neighbouring ions result in a serious pump efficiency reduction, and has to be considered in the description. The goal of this publication is to perform an optimisation of the amplifier with respect to Er- concentration and waveguide core design by including these quenching processes.

Modeling of integrated erbium doped optical amplifiers: influence of background loss and requirements to process control

An overview of the development on lossless Er-doped Y-branches and high gain Er-doped waveguide amplifiers is given, and their applications in future prospects are reviewed. A comprehensive model is presented for the integrated Er-doped phosphate silica amplifier, that includes high concentration ion-ion interaction. The model is applied to a rigorous design optimization of high gain amplifiers, where the influence of variations in the launched pump power, the core cross-section, the waveguide length, the Er-concentration, and the background loss are evaluated. Optimal design proposals are given and the process reproducibility of the proposed design is examined. Requirements to process parameter control in the fabrication of the Er-doped waveguide are also set up.