Telefonaktiebolaget Lm Ericsson (publ)

Asea Aktiebolag

Institutet for Optisk Forskning

Leif G Stensland

Torgny Brogardh

Magnus Johansson

Lars Helge Thylen

Torsten Augustsson

Georges Borak

Mats Granberg

Gunnar Arvidsson

Goran Ljungqvist

Anne Ingrid Lidgard

K A Berg

Optical elements utilize multimode interference in a piece of an optical fiber of multimode type having a core in the shape of a ring or a tubular structure. Such a fiber can be compared to a planar waveguide, the core of which has been bent about a longitudinal axis located at some distance from the core. Such an optical fiber can be optically excited having an excitation centre in a point on or at the annular core by coupling from a single-mode fiber. Then different optical propagation modes are excited having approximately regular relations between their phase velocities so that, for example, for a suitable length of the fiber piece a light intensity is obtained in the other end of the fiber piece which is an approximate reflected image of the light intensity supplied at the input end of the fiber piece. Such an optical element can, for example, be used as a filter or as a passive 1&times;N-coupler, where in the latter case the length of the fiber piece is adapted so that an N-fold image of the supplied light intensity is obtained at the output end of the fiber piece.

Optical element using multimode interference

Splicing aged optical fibers

An optical fiber intended to be used as a sensor is of the kind suitable for communication and has a longitudinal cavity or hole which can be intentionally closed or has a more narrow shape at definite positions in the longitudinal direction of the fiber. The cavity, the diameter of which can be of the magnitude of order of 5 .mu.m-50 .mu.m, is filled with a material changing its volume depending on physical quantities in the fiber environment. The hole can be closed or made narrower at different positions in the longitudinal direction of the fiber for instance by locally heating the fiber by a pulsed laser beam.

Optical fiber for sensors including holes in cladding

Lensless spectrum analyzer

The invention relates to an optical measuring device for measuring physical magnitudes such as position, speed, acceleration, force, pressure, elongation, temperature, etc., comprising at least one optical fiber for conducting light between an electronic unit and a transducer forming an optical modulator which is directly or indirectly influenced by the quantity being measured and, in dependence thereon, modulates the light emitted to the transducer. The transducer contains at least one optical filter having spectrally varying absorbing and/or transmitting and/or reflecting characteristics within the spectra of the emitted light. The light filter generates one or more stabilizing signals for the fiber optic and optoelectronics, and possibly one or more measurement signals within one or more wavelength ranges.

Fiber optical measurement apparatus

Growing community of inventors

Jafalla, Sweden

Leif G Stensland