A system for transmission of an optical signal, the system including an optical coupler for splitting said signal into a first copy and a second copy. The optical coupler has an input for receiving the optical signal, a first output for the first copy and a second output for the second copy. The system also includes a first optical guide connected to the first output, a second optical guide connected to the second output and a superposition module for coherently superimposing the first copy and the second copy of the signal.

A system for transmission of an optical signal, the system including an optical coupler for splitting said signal into a first copy and a second copy. The optical coupler has an input for receiving the optical signal, a first output for the first copy and a second output for the second copy. The system also includes a first optical guide connected to the first output, a second optical guide connected to the second output and a superposition module for coherently superimposing the first copy and the second copy of the signal.

The invention relates to a method for stably transmitting laser radiation through an optical waveguide (3), wherein two or more modes of the laser radiation propagating in the optical waveguide (3) interfere and form a mode interference pattern in the optical waveguide, as a result of which a thermally induced refractive index grating is produced in the optical waveguide (3). It is an object of the invention to demonstrate an effective approach for stabilizing the output signal of the optical waveguide (3) in a fiber-based laser/amplifier combination at high output powers, i.e. for avoiding mode instability. The invention achieves this object by virtue of the fact that a relative spatial phase shift between the mode interference pattern and the thermally induced refractive index grating is set in the direction of propagation of the laser radiation. In addition, the invention relates to a laser/amplifier combination comprising a laser (1) and an optical waveguide (3) in the form of an amplifier fiber, wherein the optical waveguide (3) amplifies the radiation of the laser (1) propagating therein. The invention proposes an actuating element (7), which produces a predefinable relative spatial phase shift of the mode interference pattern and of the thermally induced refractive index grating in the direction of propagation of the laser radiation.

The invention relates to a method for stably transmitting laser radiation through an optical waveguide (3), wherein two or more modes of the laser radiation propagating in the optical waveguide (3) interfere and form a mode interference pattern in the optical waveguide, as a result of which a thermally induced refractive index grating is produced in the optical waveguide (3). It is an object of the invention to demonstrate an effective approach for stabilizing the output signal of the optical waveguide (3) in a fiber-based laser/amplifier combination at high output powers, i.e. for avoiding mode instability. The invention achieves this object by virtue of the fact that a relative spatial phase shift between the mode interference pattern and the thermally induced refractive index grating is set in the direction of propagation of the laser radiation. In addition, the invention relates to a laser/amplifier combination comprising a laser (1) and an optical waveguide (3) in the form of an amplifier fiber, wherein the optical waveguide (3) amplifies the radiation of the laser (1) propagating therein. The invention proposes an actuating element (7), which produces a predefinable relative spatial phase shift of the mode interference pattern and of the thermally induced refractive index grating in the direction of propagation of the laser radiation.

An optical transmitter of an optical data transmission system transmitting data through an optical fiber transmission path includes a main signal generator that converts first transmission data into a predetermined signal format to generate a first signal, a DCSK modulator that DCSK-modulates second transmission data to generate a second signal, a signal-multiplexer that performs time-division multiplexing of the first signal and the second signal, and an electro-optical converter that converts a multiplexed signal obtained by the time-division multiplexing of the signal-multiplexer from an electric signal into an optical signal, and outputs the optical signal to the optical fiber transmission path.

The present invention is directed to techniques and systems for extension of unrepeatered submarine fiber links to provide an increase in reach of unrepeatered fiber transmission. Both single channel unrepeatered systems and multiple channel unrepeatered systems can be used. The multiple channel unrepeatered systems can further employ nonlinearity compensation. The present invention is also directed to methods of signal transmission using the unrepeatered systems.

The present invention is directed to techniques and systems for extension of unrepeatered submarine fiber links to provide an increase in reach of unrepeatered fiber transmission. Both single channel unrepeatered systems and multiple channel unrepeatered systems can be used. The multiple channel unrepeatered systems can further employ nonlinearity compensation. The present invention is also directed to methods of signal transmission using the unrepeatered systems.

Embodiments of the present application relate to a method for implementing Turbo equalization compensation. The equalizer divides a first data block into n data segments, where D bits in two adjacent data segments in the n data segments overlap, performs recursive processing on each data segment in the n data segments, before the recursive processing, merges the n data segments to obtain a second data block; and performs iterative decoding on the second data block, to output a third data block, where data lengths of the first data block, the second data block, and the third data block are all 1/T of a code length of a LDPC convolutional code.

Embodiments of the present application relate to a method for implementing Turbo equalization compensation. The equalizer divides a first data block into n data segments, where D bits in two adjacent data segments in the n data segments overlap, performs recursive processing on each data segment in the n data segments, before the recursive processing, merges the n data segments to obtain a second data block; and performs iterative decoding on the second data block, to output a third data block, where data lengths of the first data block, the second data block, and the third data block are all 1/T of a code length of a LDPC convolutional code.

An optical transmitter apparatus is disclosed. The apparatus includes a processor, a memory coupled to the processor, and one or more programs configured to be executed by the processor. The programs include instructions for nonlinearity estimation that characterizes nonlinearity in an optical communication and estimates an amount of symbol distortion caused by the nonlinearity, instructions for selecting and mapping symbols to provide, for the nonlinearity estimation, only symbols that meet predetermined nonlinearity criteria, and instructions for storing, in the memory, the amount of symbol distortion to be used for a nonlinearity pre-compensation.