Leif Bjerkan

Measurement of laser parameters for simulation of high-speed fiberoptic systems

The semiconductor laser rate equations are rewritten using a new set of parameters which can all be found from steady state and small signal measurements on the laser. Procedures for finding these parameters are described. Parameters have been measured on three 1550 mm lasers from different manufacturers. Comparison between large signal measurements and simulations using the measured parameters shows in general good agreement for modulation currents sufficiently above threshold.

Application of Bragg grating sensors in the characterization of scaled marine vehicle models

Experiments using two different fiber-optic Bragg grating strain sensor systems to measure dynamic loads, slamming forces, and bending moments on a scaled catamaran model are reported. The system designed to measure slamming forces is based on dynamic locking of the laser diode wavelength to the peak wavelength of a Bragg grating mounted in a force cell. The sensor system has a dynamic range of 27 dB (1-550 N) and a bandwidth in excess of 1 kHz. For the measurement of bending moments, a time-domain multiplexing system, which used a unique pulsed rf modulation technique, of two Bragg grating sensors mounted on a steel beam was designed. The dynamic range of this system was also 27 dB [17 Nm (Newton meter) with a 0.03-Nm resolution]. The bandwidth was limited to approximately 50 Hz.

Application of fiber-optic Bragg grating sensors in monitoring environmental loads of overhead power transmission lines

We demonstrate the capability of using fiber-optic sensors for measurements on environmental loads on a high-power, overhead transmission line. A trial system with three Bragg gratings, including a temperature reference, was installed on a 160-m span of a 60-kV line. An interrogation system with a tunable distributed Bragg reflector laser source was used. Several measurements of the induced loads on a conductor were recorded in various wind conditions. In particular, aeolian vibrations were frequently observed, and several measurements of this phenomenon were made. The results correlate well with simple theoretical predictions and visual observations.

Fiber-optic sensor for real-time monitoring of temperature on high voltage (400KV) power transmission lines

On-line monitoring of temperature and sag in 400KV power transmission line has successfully been implemented by a novel device using fibre Bragg grating (FBG) sensors. The complete device has been fabricated with aluminum mount connected via fibre-optic cable and installed on ACSR power conductor for continuous two years measurement. This paper presents the excellent results and experience of the tests in controlled indoor environments conducted in Norway and real-field application on installed power conductor in India. Thus, better surveillance of the thermal and mechanical loads on power lines can be possible using this FBG sensor system.

Optical fiber splice loss predictions from one-way OTDR measurements based on a probability model

It is well known that one-way optical time-domain reflectometry (OTDR) measurement contains a false contribution to the splice loss due to statistical fluctuations in light scattering among fibers. Using a large amount of collected data over splice losses from field installations, a two-dimensional probability distribution function with the actual splice loss and the one-way measured OTDR discontinuity as variables was fitted to the data. The five parameters of the chosen probability distribution were determined numerically from the observed data. The probability of keeping the splice loss below a target value based on the observed one-way OTDR reading was calculated and can be displayed in a curve or a table of values. The agreement between theory and experimental values is satisfactory for standard match clad single-mode fibers measured at 1.3- mu m wavelength. >

Measurements of frequency responses of three-section distributed Bragg reflector lasers and application to modulation spectroscopy

Abstract The feasibility for wavelength modulation spectroscopy using a three-section distributed Bragg reflector (DBR) laser modulated at the phase section has been investigated. The FM and AM responses have been measured versus frequency from dc to 3 GHz at various positions on the tuning curve. The modulation efficiency as a function of the tuning currents combined with modulation frequency has been studied. In particular the behaviour at the positions of laser mode jumps has been emphasised as well as consistency of the recorded spectra across the entire tuning range. These tests were performed with a tuneable Fabry–Perot filter. The operation conditions were adapted for high and sustained FM response for modulation spectroscopy over a wide wavelength range. A conventional Bragg grating is used as an example of practical application.

Measurements of overhead transmission line loads with Bragg gratings

Three Bragg gratings including a temperature reference have been installed on a 160 m long overhead conductor span carrying 60 kilovolts. Measurements on wind-induced loads like vibrations and forces from steady winds are reported.

Experiments with Fiberoptic Smart Skin Sensors Applied to Marine Vehicles

Advanced composite materials are currently finding an increased use in marine vehicle construction. The introduction of new materials reduces hull weight, and is especially attractive for fast vehicles. By the introduction of new materials a need arises to design a cost effective construction which can withstand expected environmental stresses under operation with an optimum use of material for reinforcement. Furthermore, it is desired to monitor the long term integrity of the new materials when subjected to sea loads under operation. Data collected on these composite materials are still rather limited.