Nonlinear Companding Circuits With Thermal Compensation to Enhance Input Dynamic Range in Analog Optical Fiber Links

J. Rodriguez–Rodriguez*¹, J. Velazquez–Hernández¹

¹ Instituto de Investigaciones Eléctricas, Control and Instrumentation Department Reforma 113, Col. Palmira, 62490 Cuernavaca, Morelos, México *E–mail: jrr@iie.org.mx

ABSTRACT

Measuring systems based on a pair of optical fiber transmitter–receivers are used in medium–voltage testing laboratories wherein the environment of high electromagnetic interference (EMI) is a limitation for using conventional cabling. Nonlinear compensation techniques have been used to limit the voltage range at the input of optical fiber links. However, nonlinear compensation introduces gain and linearity errors caused by thermal drift. This paper presents a method of thermal compensation for the nonlinear circuit used to improve transient signal handling capabilities in measuring system while maintaining low errors in gain and linearity caused by thermal drift.

Keywords: Nonlinear compensation, thermal compensation, optical fiber link, high power testing, input dynamic range.

RESUMEN

Los sistemas de medición basados en un par de transmisores–receptores de fibra óptica se utilizan en los laboratorios de pruebas de media tensión, en donde el ambiente de alta interferencia electromagnética (EMI) es una limitación para el uso de cableado convencional. Técnicas no lineales de compensación se han utilizado para limitar el rango de voltaje en la entrada de enlaces de fibra óptica. Sin embargo, la compensación no lineal presenta errores de ganancia y linealidad causados por la deriva térmica. Este trabajo presenta un método de compensación térmica para el circuito no lineal utilizado para mejorar las capacidades de manejo de señales transitorias en el sistema de medición, manteniendo bajos los errores en la ganancia y linealidad causados por la deriva térmica.

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