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Abstract

The invention relates to a Kerr type optical modulator and to an all-optical clock recovery circuit operating by active mode locking of a fiber loop laser including such a modulator. Operation is independent of the polarization of the signals presented to the signal input, at wavelength .lambda..sub.s. The wavelength of the clock signal delivered by the clock recovery circuit is .lambda..sub.c. The modulator comprises an even number of segments, and in a preferred embodiment four segments of polarizationmaintaining fiber, with the segments being of equivalent optical lengths, and interconnected by three splices at three locations. At the first and third splices, the neutral propagation axes of the polarization-maintaining fiber are turned through 90.degree.. In an advantageous variant of the invention, a mode converter is inserted in the loop at the second splice, the mode converter comprising an optical demultiplexer and an optical multiplexer together with two polarization-maintaining optical paths interconnecting them. The demultiplexer separates the two different-wavelength optical signals present in the loop of the fiber laser and applies them respectively to said two paths. A splice including 90.degree. rotation of the neutral axes of the polarization-maintaining fibers is made on the path conveying the input signal at wavelength .lambda..sub.s. On the other path, there is no rotation of the axes. The multiplexer then recombines the two signals. The invention is applicable to long distance telecommunications via optical fiber.

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First Claim