Abstract: A method and system for performing a secure key relay of an encryption key, Kenc, provided by an initial node, KN0, and used by an encoding unit (ENC) of a first data transceiver for encoding plain data, Pdata, to provide encrypted cipher data, Cdata, transported via a data transport link, DTL, to a decoding unit (DEC) of a second data transceiver which decodes the transported cipher data, Cdata, using the relayed encryption key, Kenc, provided by a terminal node, KNN, as a decoding key to retrieve the plain data, Pdata, wherein the relay of the encryption key, Kenc, from the initial node, KN0, to the terminal node, KNN, is performed by means of intermediate relay nodes, KN1, KN2 . . . KNN?1, and comprises the steps of sharing (S1) QKD-keys, K, between the nodes via secure quantum channels, QCH, of a quantum key distribution network, QKDN; performing (S2) encryption of shared QKD-KEYS, K, at the initial node, KN0, and at each intermediate relay node, KN1, KN2 . . .

Abstract: A method for bi-directionally transmitting digital optical signals over an optical transmission link in which a first optical transmit signal is created according to a first binary digital signal in such a way that the bit information of the first binary digital signal is included in first sections of the symbol interval of the first optical transmit signal. A second optical transmit signal is created by creating an optical wavelength reuse signal using the first optical transmit signal received at the second end of the optical transmission link, the optical wavelength reuse signal being modulated according to a second digital signal in such a way that the bit information of the second digital signal is included in second sections of the symbol interval of the first optical transmit signal received.

Abstract: A method for bi-directionally transmitting digital optical signals over an optical transmission link in which a first optical transmit signal is created according to a first binary digital signal in such a way that the bit information of the first binary digital signal is included in first sections of the symbol interval of the first optical transmit signal. A second optical transmit signal is created by creating an optical wavelength reuse signal using the first optical transmit signal received at the second end of the optical transmission link, the optical wavelength reuse signal being modulated according to a second digital signal in such a way that the bit information of the second digital signal is included in second sections of the symbol interval of the first optical transmit signal received.

Abstract: A receiving apparatus and method for processing a differential phase shift keying signal carrying a plurality of symbols are disclosed to provide for improved compensation of linear and non-linear noise in phase modulated optical transmission. The receiving apparatus comprises an input unit for receiving electrical signals derived from an optical signal and a calculation unit for calculating a current value of a decision variable. The current value is indicative of a differential phase shift in the optical signal between a currently received symbol and a previously received symbol as a function of the optical signal power of the optical signal for the currently received symbol and at least one previous value of the decision variable. The receiving apparatus also comprises a decision unit for determining the differential phase shift from the current value of the decision variable obtained from the calculation unit to obtain the currently received symbol.

Abstract: A device that detects an effect which distorts a communication signal in a serial communication channel comprises an input, a detector connected to the input, a demultiplexer having a data input connected to the output of the detector, and an evaluator at each output of the demultiplexer. The input receives the distorted communication signal from the communication channel. The detector detects a feature in a symbol of the distorted communication signal and outputs the detected feature. The demultiplexer outputs the detected feature and has a plurality of control inputs. A differently delayed symbol (i?1, 1, i+1) of the communication signal is applied to each input to switch the detected feature present at the input of the demultiplexer to an output of the demultiplexer specified by the symbols present at the control inputs.

Abstract: A transmitter for an optical RZ-DPSK communication signal comprises a source for an optical carrier, an electro-optical modulator which comprises at least one element having an optical path length adapted to be varied by an electrical driver signal for intensity modulating the optical carrier based on the driver signal, and a driver circuit for generating the driver signal from an electrical communication signal. The driver signal is an impulse-type signal having two types of impulses spaced in time by a neutral signal state, wherein in the presence of the neutral state of the driver signal at the modulator, the transmission of the modulator becomes zero, and the two types of impulses each cause a transmission different from zero and a phase which is specific for the type of the impulses in the modulator.

Abstract: A receiving apparatus and method for processing a differential phase shift keying signal carrying a plurality of symbols are disclosed to provide for improved compensation of linear and non-linear noise in phase modulated optical transmission. The receiving apparatus comprises an input unit for receiving electrical signals derived from an optical signal and a calculation unit for calculating a current value of a decision variable. The current value is indicative of a differential phase shift in the optical signal between a currently received symbol and a previously received symbol as a function of the optical signal power of the optical signal for the currently received symbol and at least one previous value of the decision variable. The receiving apparatus also comprises a decision unit for determining the differential phase shift from the current value of the decision variable obtained from the calculation unit to obtain the currently received symbol.

Abstract: A forward error correcton coding method comprises a generalized concatenated code comprising a plurality of outer component codes and a plurality of inner component codes. The outer components codes comprise Reed-Solomon codes and a plurality of binary codes of equal length but varying rates. The inner component codes have a nested structure and are defined by the sum of disjoint Bose-Chaudhuri-Hocquenghem (BCH) codes. The inner and outer component codes are selected such that the product of the minimum Hamming distances of the inner and outer component codes are as equal as possible. Moreover, the component codes are selected by matching cyclotomic cosets of inner BCH codes and type and multiplicity of outer codes.

Abstract: A forward error correcton coding method comprises a generalized concatenated code comprising a plurality of outer component codes and a plurality of inner component codes. The outer components codes comprise Reed-Solomon codes and a plurality of binary codes of equal length but varying rates. The inner component codes have a nested structure and are defined by the sum of disjoint Bose-Chaudhuri-Hocquenghem (BCH) codes. The inner and outer component codes are selected such that the product of the minimum Hamming distances of the inner and outer component codes are as equal as possible. Moreover, the component codes are selected by matching cyclotomic cosets of inner BCH codes and type and multiplicity of outer codes.

Abstract: A transmitter for an optical RZ-DPSK communication signal comprises a source for an optical carrier, an electro-optical modulator which comprises at least one element having an optical path length adapted to be varied by an electrical driver signal for intensity modulating the optical carrier based on the driver signal, and a driver circuit for generating the driver signal from an electrical communication signal. The driver signal is an impulse-type signal having two types of impulses spaced in time by a neutral signal state, wherein in the presence of the neutral state of the driver signal at the modulator, the transmission of the modulator becomes zero, and the two types of impulses each cause a transmission different from zero and a phase which is specific for the type of the impulses in the modulator.

Abstract: Antitumor peptides of the formula ##STR1## where R.sup.1, R.sup.2, R.sup.3, R.sup.4 and R.sup.5 have the meanings stated in the description, and the preparation thereof.