Research and development of 40 GHz bandwidth laser relative intensity noise measurement system using PID controller and ESA spectrum analyser

Abstract

Measuring and evaluating the quality of laser sources used in optical communications and in the precision
measurement system is essential. Relative intensity noise (RIN) is a parameter that directly affects the
system quality. Therefore, RIN needs to be measured periodically. This study presents a high-sensitivity,
broadband (40 GHz) RIN measurement system using a precisely temperature-controlled photodetector and
an electrical spectrum signal analyser. RIN value is determined through indirect measurement of noise
components: thermal noise, total detected noise, and the shot noise of the laser source. These noises are measured by using an Electrical spectrum analyser (ESA) and a super sensitive 61/2 digital multimeter (DMM). The experimental results of the RIN measurement of the reference Distributed feedback (DFB) laser source show the similarity between the RIN value measured by the system and the RIN value provided by the manufacturer.