Torsten Gogolla

Spontaneous Raman scattering in optical fibers with modulated probe light for distributed temperature Raman remote sensing

Long-length fiber-optic remote Raman sensors are used for distributed temperature measurements. Toward this aim, we apply optical-fiber frequency-domain reflectometry. The Raman intensity generated in single- and multimode optical fibers is theoretically investigated for sinusoidally intensity-modulated probe light. Thus, a proper sensor element and wavelength for fiber-optic Raman sensing is determined. Further, the temperature error for long sensor fibers is theoretically analyzed.

Distributed beat length measurement in single-mode optical fibers using stimulated Brillouin-scattering and frequency-domain analysis

We present a method for distributed measurement of beat length, differential group delay, strain, and temperature in long length single-mode optical fibers. Toward this aim, we employ the polarization state sensitive effect of stimulated Brillouin scattering (SBS). The distributed measurement is realized by applying frequency-domain analysis. We present the analytical relationships between the Brillouin interaction of two counterpropagating waves in the fiber and the polarization states. Experimental results confirm the ability of the method to measure distributed beat length.