Intra-cavity measurement concept of dispersion properties with a tunable fiber-integrated laser

The dispersion properties of fibers depict a key characteristic to model the propagation of ultra-short pulses in waveguides. In the following, a new method is presented to directly measure the dispersion properties of fibers and optical components in the time domain. The analysis is based on pulse shape variations along the tuning range of a theta cavity fiber laser (TCFL) depending on the adjusted repetition rate. The automated measurement procedure, evaluating pulse symmetry, achieves a temporal sensitivity below 5 ps surpassing the resolution of the acquisition electronics. Exemplarily, two samples of Nufern PM980-XP fiber are investigated with an Yb-doped tunable TCFL retrieving the mean dispersion parameter D? by comparative measurements. The obtained results are compared to a reference method based on spectral interferometry. With deviations in D? between either approach of 0.3% and 1.3%, respectively, the results agree well within the measurement errors of the TCFL, verifying the presented concept. Due to the pulse formation process extending over multiple round trips, this approach achieves an enhanced sensitivity compared to competing direct temporal methods. Together with an alignment free operation, the fiber-integrated TCFL depicts a simple and robust concept showing potential in specific measurement scenarios such as in quality management. © 2019 Astro Ltd

Guideline for Use of Fibre Optic Sensors

Development of standards and guidelines for performance specifications and testing for fibre optic sensors has been discussed since the mid-nineties of the last century in the scientific community as well as in the industry. Very global standards for the use of fibre optic components in data communication and telecommunication have been available for more than 20 years. Guidelines or substantial standards for fibre optic sensors are rather an exception. The first standard draft on generic specification of fibre optic sensors has been published in 1995 (IEC 61757-1:1995); the first draft for a specific type of fibre sensor - the fibre optic gyroscope - was published in 1996 (IEEE Standard Specification Format Guide and Test Procedures for Single-Axis Interferometric Fiber Optic Gyros; Working Draft P952/D24). Some terms used in fibre optic communication are quite close to the terminology typically used in fibre optic sensor technology. However, there are a huge number of specific issues associated with specifically fibre optic sensing systems. These items are not considered in existing guidelines or standards. For instance, standards for fibre optic sensors have to cover characteristic details related to the respective physical sensor mechanism, to the sensor response for different measurands, to the application, and finally to specific environmental conditions. Naturally, it is not possible to cover either all different aspects of fibre optic sensors in one standard or a set of harmonized standards. This very complex matter requires specific guidelines for specific sensor types (e.g. distributed sensors, point sensors such as fibre Bragg grating (FBG) sensors, sensors for mechanical measurands such as strain, deformation, biological and chemical sensors or sensors for physical quantities such as pressure, humidity, and ionizing radiation). In order to define clear guidelines and/or regulations for appropriate characterization of performance specifications and better understanding of frequently used fibre optic sensors, particular activity has been established within the European COST Action 299 “FIDES” (Optical Fibres for New Challenges Facing the Information Society) in the framework of its Working Group 4: “New Challenges in Fibre Optic Sensors”

Guidelines for the characterization and use of fibre optic sensors: basic definitions and a proposed standard for FBG-based strain sensors

This paper describes the outcome of two groups which are involved in the specification of guidelines for fibre optic sensors performance and testing. The "Guideline for use of fibre optic sensors" from the COST-299 guideline group, and the "Optical Strain Sensor based on Fibre Bragg Grating" from the GESA guideline group of the VDI - "The Association of German Engineers". Through appropriate specifications and definitions, both guidelines aim at enabling better understanding of fibre optic sensors characteristics and performances. A concise view into the structure of the guidelines is presented, emphasizing important aspects. The English version of the two guidelines will be available in autumn 2009