F. Parvaneh

Frequency-derived remote measurement of birefringence in polarization-maintaining fiber by using the optical Kerr effect

A technique to measure remotely the birefringence of polarization-maintaining fiber is described. The method uses a pump-and-probe scheme that employs the optical Kerr effect together with a small wavelength difference between the sources to allow a measurable derived frequency to be generated. The frequency depends on the birefringence of the fiber and the source wavelength offset. This latter feature provides a tunable frequency and hence an extra degree of freedom in the system design.

Advances in distributed optical fibre sensing

The ability to make distributed measurements on extended structures is of increasing importance. For example, the measurement of strain distribution on aircraft operating close to their performance limits, the distribution of temperature in boilers, pressure vessels, high voltage transformers etc.,

Single-shot distributed optical-fiber temperature sensing by the frequency-derived technique

We present, for the first time to our knowledge, a distributed optical-fiber temperature sensor, based on a pulsed laser, that provides distributed temperature measurement by use of a single pulse propagating in an optical fiber. The system uses the frequency-derived technique based on the optical Kerr effect. The performance of the system is investigated for the temperature range 33-150 degrees C. A linear relationship between the temperature and the derived frequency is obtained. The best temperature resolution was determined to be +/-1.2 degrees C. The best measured spatial resolution was 0.56 m.

Frequency-derived distributed optical-fiber sensing technique: theory and characterization

Frequency-derived distributed optical-fiber sensing is a method for remote measurement of the spatial distribution of linear birefringence in an optical fiber, allowing a corresponding measurement of those external measurands that influence this birefringence. The method employs a pump-probe scheme, which, by use of the optical Kerr effect, generates an optical modulation of the probe beam, with a modulation frequency whose temporal variation maps the spatial distribution of birefringence. We provide a complete theoretical analysis of this method by using Jones calculus and graphic representation on the Poincaré sphere. The relevant characterization of the technique and some experimental results are also presented; these show good agreement with the theory.

Analysis of frequency-derived measurement of linear birefringence in optical fibres

We have recently demonstrated1-3 that the optical Kerr effect can be used in pulsed-pump, cw- probe configurations to detect changes in the linear birefringence of single mode optical fibres. This phenomenon can be used in different ways to detect the presence of stress in the fibres, to locate the stress and to measure the magnitude of the associated birefringence changes as a function of position along the fibre.

Frequency-derived distributed optical fiber sensing: backscatter analysis

Frequency-derived distributed optical-fiber sensing is a powerful and convenient method for measuring the spatial distribution of birefringence in a hi-bi fiber. The method relies on the special statistical characteristics of Rayleigh backscatter for its action, and these are analyzed in the context of the system. Some preliminary experimental results are also reported.