Abstract: The invention relates to a router which may be used for amplification of a bidirectional optical signal using a single optical amplifier. An advantageous embodiment of the invention comprises two 3 dB couplers which are serially connected via a delay element. According to the embodiment, the delay element comprises a difference in distance L between the two optical branches which connect the two 3 dB couplers.

Abstract: The invention relates to a router which may be used for amplification of a bidirectional optical signal using a single optical amplifier. An advantageous embodiment of the invention comprises two 3 dB couplers which are serially connected via a delay element. According to the embodiment, the delay element comprises a difference in distance ?L between the two optical branches which connect the two 3 dB couplers.

Abstract: The invention relates to a method and a modulator circuit for modulating light in a modulator circuit. The modulator circuit comprises a Mach-Zehnder modulator having at least one optical input and at least one optical output, said Mach-Zehnder modulator modulating light, which is fed to the input of the Mach-Zehnder modulator in response to applied electrical modulation signals from a driver circuit. According to a method of the invention, the applied modulation signal on the electrodes of the Mach-Zehnder modulator is superimposed by a pilot tone which is thus superimposed by the modulated light emitted by the Mach-Zehnder modulator. In response to the emitted modulated light, an electrical feedback circuit generates bias control signals for the bias circuit and driver control signals for the driver circuit for regulating the bias signal and the driver signal fed to the Mach-Zehnder modulator.

Abstract: A method for ensuring that modules to be connected to an apparatus comprising a processor are of a specific type, includes providing these modules with a code circuit capable of outputting one or more code words on request. When a module has been connected to the system, the processor of the apparatus reads one or more of the code words from the code circuit of the module, compares the read code word or words with reference code words stored in the apparatus, and rejects the module if the read code word or words do not correspond to the reference code words. A large number of different code words are stored in the code circuit of the specific type, and the code circuit is moreover adapted such that a code word can be output correctly only after the lapse of a prefixed period of time, which is considerably longer than a normal output time determined by the implementation of the code circuit, after a previous output of a code word.

Abstract: The invention relates to a router which may be used for amplification of a bidirectional optical signal using a single optical amplifier. An advantageous embodiment of the invention comprises two 3 dB couplers which are serially connected via a delay element. According to the embodiment, the delay element comprises a difference in distance &Dgr;L between the two optical branches which connect the two 3 dB couplers.

Abstract: A method of transmitting data signals via an optical fiber between two network elements (14, 36, 43, 56) in a digital data transmission network comprises using a transmission protocol, wherein, in addition to said data signals, first control and/or monitor signals in the form of overhead signals are transmitted. An optical fiber amplifier (23) is inserted in the optical fiber between the two network elements. Additionally, second control and/or monitor signals in a format corresponding to said overhead signals are transferred between the optical fiber amplifier and at least one of the two network elements. An amplifier unit (22, 48) comprising an optical fiber amplifier (23) is adapted to be inserted in an optical fiber for the transmission of data signals between two network elements (14, 36, 43, 56) in such a data transmission network.

Abstract: In a method of amplitude equalization of a plurality of optical signals having mutually different wavelengths, the optical signals are launched into a first end of an optical fiber (5). The optical signals are amplified, before being launched into the fiber (5), to a level at which at least one of the signals exceeds a stimulated Brillouin scattering (SBS) threshold value (TSBS) characteristic of the fiber, so that part of the signal energy in the fiber is transferred to a Stokes signal propagating in the fiber (5) in a direction opposite to said optical signals. An apparatus for amplitude equalization of a plurality of optical signals having mutually different wavelengths comprises an optical fiber (5) having an input end (6) where said optical signals may be supplied to the fiber, and an output end (10) where said optical signals may be tapped from the fiber after equalization.

Abstract: The invention relates to a method and a modulator circuit for modulating light in a modulator circuit. The modulator circuit comprises a Mach-Zehnder modulator having at least one optical input and at least one optical output, said Mach-Zehnder modulator modulating light, which is fed to the input of the Mach-Zehnder modulator in response to applied electrical modulation signals from a driver circuit. According to a method of the invention, the applied modulation signal on the electrodes of the Mach-Zehnder modulator is superimposed by a pilot tone which is thus superimposed by the modulated light emitted by the Mach-Zehnder modulator. In response to the emitted modulated light, an electrical feedback circuit generates bias control signals for the bias circuit and driver control signals for the driver circuit for regulating the bias signal and the driver signal fed to the Mach-Zehnder modulator.

Abstract: In a method of transferring data packets between a plurality of network elements (14; 28) in a teletransmission network (1), at least some data packets are transferred at a bit rate which depends on available network capacity. When arriving at a network element, packets are positioned in a plurality of input queues (33; 37). Then, the packets are transferred from the input queues (33; 37) to at least one output queue (38) at a bit rate which is regulated by a factor (&lgr;) which depends on the filling degree of the output queue.