Abstract: A method and device for reducing the distortion of optical pulses caused by the polarization mode dispersion in optical communication systems is provided. When an optical pulse having any polarization is transmitted through an optical communication system, which is optically anisotropic, at least in sections, the optical pulse may become distorted due to the different velocities of the various polarization components. This distortion of the optical pulses may reduces the maximum transmission rate of the system. A method is provided for functioning in response to the detected transmission quality of the communication system where a polarization-controlling device for setting the polarization of the optical pulse is driven in such a way that the transmission quality is maximized. An optical communication system, including an optical transmission medium, involves a device for determining the transmission quality of the communication system, a regulating device, and a polarization-controlling device.

Abstract: In a method for measuring relevant parameters of individual fibers of single-mode and multimode fibers of glass- or plastic-fiber cables, measuring radiation is reflected at the end of the test fiber to the fiber input by a mirror, particularly a Schmidt mirror having very high reflectivity (>99%), the measurement being carried out at the coupling-in site by a combined transmitting and receiving device. The Schmidt mirror is connected to the test fiber via a so-called fiber connector. The highly reflective mirror coating is applied to the end face of a given connector, so that the Schmidt connector provided with the mirror coating is connected to the test fiber either directly or via a short glass-fiber cable piece terminated with a standard connector and with the Schmidt mirror connector. With the use of a glass-fiber cable piece thus terminated the Schmidt mirror connector remains untouched and is protected.

Abstract: The phase modulator in the laser resonator requires both at the input and at the output defined linearly polarized light which has to be generated. Hitherto, this was bought about in a complex and expensive manner using polarization actuators. The invention provides a combination of dispersion compensation and definition of the linear polarization state in a dispersion compensation fiber (PM-DC fiber) which is birefringent at such a high level that only the two orthogonal linear polarization states can be diffused therein. The invention can be used for mode-locked fiber lasers in which the time pulse width has to be as small as possible.

Abstract: A method and a system for carrying out control and monitoring measurements on optical transmission paths which can be used during regular operation and without disturbing the same to measure and control parameters of the transmission path as well as to monitor the transmission path with respect to tapping attempts. A control signal having wavelength that is different from the transmission signal into the transmission path, re-reflected after propagating through the transmission path and analyzed. To reflect the control signal, a wavelength-selective reflecting set-up, such as a dichroic reflector is used, which transmits the transmission signal substantially as an undisturbed signal. The reflected control signal is detected by a detecting device and analyzed with respect to polarization, intensity, signal shape, or other properties, making it possible to infer the properties of the transmission path and/or detect unwanted tampering with the transmission system.

Abstract: The present invention relates to an optical single-mode fiber having low dispersion for the wavelength division multiplex operation (WDM) of an optical transmission path, which is made of a central fiber core having the radius r1, two inner fiber cladding layers having the outer radius r2 and a, respectively, where a>r2, and an outer fiber cladding layer, the refractive index profile n(r) of the fiber not being constant as a function of the fiber radius r (triple-clad fiber). By properly selecting the profile form and the refractive index differences between the core layers and cladding layers, respectively, conventional fabrication methods can be used to manufacture a fiber having low dispersion within the wavelength range of about 1400 to 1700 nm and, thus, in the third optical window, fiber attenuation not being increased thereby.

Abstract: A method of manipulating a compensation fiber for compensating the high negative dispersion of a fiber laser in the second optical window. The active fiber of the fiber laser is linked to a compensation fiber which consists of a step-index quartz glass core with a sheathing. By doping the compensation fiber sheathing with fluorine in a targeted manner, a positive value is set for the dispersion of the compensation fiber. Subsequent dimensioning of the length of the compensation fiber increases the set dispersion value to the positive dispersion value necessary for complete compensation of the dispersion of the fiber laser.

Abstract: The phase modulator in the laser resonator requires both at the input and at the output defined linearly polarized light which has to be generated. Hitherto, this was bought about in a complex and expensive manner using polarization actuators. The invention provides a combination of dispersion compensation and definition of the linear polarization state in a dispersion compensation fiber (PM-DC fiber) which is birefringent at such a high level that only the two orthogonal linear polarization states can be diffused therein. The invention can be used for mode-locked fiber lasers in which the time pulse width has to be as small as possible.

Abstract: A method and a device are described to compensate for polarization mode dispersion in an optical transmission link(9, 9′) having polarization-dependent transmission characteristics, in particular in optical fibers and cables with not only statistical, but preferred birefringence. A compensation element (1, 1′, 1″), whose length is adjusted non-destructively using an interference device (2, 2′, 2″), in particular a pressure mechanism, is connected upstream or downstream from the transmission link (9, 9′). The polarization states PL and PS of the compensation element are mixed by the interference and thus the length of the compensation fiber is defined at which a propagation time difference between the partial waves of polarization states PL and PS is increased or decreased so that it compensates for the propagation time difference &tgr; within the transmission link (9, 9′).