Abstract: Provided is a method for monitoring a pump laser of at least one optical amplifier in an optical transmission link in operation. The optical output power of the pump laser to be monitored depends on an injection current. The pump laser to be monitored is operated at an operating point defined by a given value of the injection current and a corresponding value of the optical output power. The method includes the steps of shifting the operating point of the pump laser to be monitored to at least one shifted operating point. The shifting is effected in such a way that the gain of the respective optical amplifier essentially reaches its steady state, determining information on the at least one shifted operating point, and using the information on the operating point and the at least one shifted operating point to determine information on the stage of aging of the pump laser to be monitored.

Abstract: Provided is a method for reducing the impact of transient effects in an optical network. The optical network includes at least one span, and an optical signal having a plurality of sub-bands travels through at least one span of the at least one span of the optical network. Each of the at least one span has associated amplifiers and the associated amplifiers are connected to launch optical signals into a remainder of a corresponding optical transmission line. Respectively one of the sub-bands of the optical signal traveling through the span is amplified by one of these associated amplifiers. Each of the associated amplifiers includes at least one control element for controlling gain and tilt of the corresponding amplifier.

Abstract: The disclosure relates to a method, an optical receiver and an optical system for compensating, at an optical receiver, signal distortions induced in an optical carrier signal by a periodic copropagating optical signal, wherein the optical carrier signal and the copropagating signal copropagate at least in part of an optical system or network, by: receiving, at the optical receiver, the optical carrier signal, wherein the optical carrier signal is distorted by the copropagating signal; determining, at the optical receiver, a period of a periodic component of the distorted optical carrier signal; determining, at the optical receiver, a periodic distortion of the distorted optical carrier signal; and generating a compensation signal to correct the distorted optical carrier signal according to the determined periodic distortion.

Abstract: Disclosed herein is a method of encoding and/or decoding data for optical data transmission along a transmission link, as well as corresponding transmitters and receivers. The data is encoded based on an adaptive constellation diagram in a 2-D plane, said constellation diagram including a first and a second pair of symbols, wherein the symbols of the first pair of symbols are located at opposite sides of the origin of the 2-D plane at a first distance di from each other, and wherein the symbols of the second pair of symbols are located at opposite sides of the origin of the 2-D plane at a second distance d2 from each other. The method comprises a step of adapting the constellation diagram by varying the ratio of the first and second distances d1, d2 such as to minimize or nearly minimize a bit error rate in the transmitted data.

Abstract: Disclosed herein is a transponder comprising a transmitter and a receiver. The transponder further comprises a receiver input amplifier, a bypass line, and a control unit configured for determining the performance of the transponder in relation to an OSNR related parameter, by controlling the transponder to generate a noise signal to be received by the receiver. The receiver input amplifier is operated to thereby cause ASE in the receiver input amplifier to facilitate the determination. A test signal is generated at the transmitter Said noise signal and said test signal, and/or one or more respective replicas thereof, are superimposed to form a combined signal to be received by said receiver to further facilitate determination of said performance related parameter based on said combined signal, wherein for generating said combined signal, said test signal is fed from the transmitter to the receiver by means of said bypass line.

Abstract: A Raman pumping device (10) for amplifying a data optical signal in a fiber optic transmission system, comprising first and second ports (12a, 12b) through which the data optical signal may respectively enter and exit the Raman pumping device (10), a Raman pump source (14) for generating a Raman pump signal, and at least one combiner (16) for combining the Raman pump signal with the data optical signal. The Raman pumping device (10) allows for selectively combining the Raman pump signal generated by the same Raman pump source (14), or at least parts of the same Raman pump source (14) codirectionally or counterdirectionally with the data optical signal.

Abstract: The disclosure relates to a method, an optical receiver and an optical system for compensating, at an optical receiver, signal distortions induced in an optical carrier signal by a periodic copropagating optical signal, wherein the optical carrier signal and the copropagating signal copropagate at least in part of an optical system or network, by: receiving, at the optical receiver, the optical carrier signal, wherein the optical carrier signal is distorted by the copropagating signal; determining, at the optical receiver, a period of a periodic component of the distorted optical carrier signal; determining, at the optical receiver, a periodic distortion of the distorted optical carrier signal; and generating a compensation signal to correct the distorted optical carrier signal according to the determined periodic distortion.

Abstract: A method for determining the position of an irregularity in an optical transmission fiber using an optical time domain reflectometer, the method comprising the steps of emitting a succession of sampling light pulses into the optical transmission fiber, detecting reflected light pulses resulting from the reflection of the sampling light pulses at the irregularity in the optical transmission fiber and generating corresponding time-dependent detection signals, wherein different delays are associated with detection signals corresponding to different sampling light pulses, obtaining a combined signal from the detection signals, and analyzing the combined signal for determining the position of the irregularity in the optical transmission fiber with respect to the optical time domain reflectometer, wherein the combined signal corresponds to a superposition of the detection signals.

Abstract: The invention discloses a method of amplifying an optical signal, in particular a data signal, transmitted from a first location (A) to a second location (B) via a first transmission link (10a), wherein said optical signal is amplified by means of a transmitter side remote optically pumped amplifiers (ROPA) (18) comprising a gain medium (24), wherein the gain medium (24) of said transmitter side ROPA (18) is pumped by means of transmitter side pump power (20) provided from said first location (A), characterized in that at least a part of said transmitter side pump power (20) is provided by means of light supplied from said first location (A) to said transmitter side ROPA (18) via a portion of a second transmission link (10b) provided for transmitting optical signals from said second location (B) to said first location (A).

Abstract: Disclosed herein is a method of transmitting a data stream from a first location to a second location through an optical network, as well as a corresponding performance monitoring unit, a transmitting arrangement and a receiving arrangement.

Abstract: Disclosed herein is a method of encoding and/or decoding data for optical data transmission along a transmission link, as well as corresponding transmitters and receivers. The data is encoded based on an adaptive constellation diagram in a 2-D plane, said constellation diagram including a first and a second pair of symbols, wherein the symbols of the first pair of symbols are located at opposite sides of the origin of the 2-D plane at a first distance di from each other, and wherein the symbols of the second pair of symbols are located at opposite sides of the origin of the 2-D plane at a second distance d2 from each other. The method comprises a step of adapting the constellation diagram by varying the ratio of the first and second distances d1, d2 such as to minimize or nearly minimize a bit error rate in the transmitted data.

Abstract: A method for determining a model representation for an optical transmitter comprises determining a quantity of a subsequence of output signals of an optical transmitter, the output signals being emitted in response to a sequence of input signals provided to the optical transmitter, and determining a model representation for the optical transmitter based on the determined quantity, wherein the quantity only represents a part of the information encoded in the subsequence of the output signals.

Abstract: Disclosed herein is a transponder (14), comprising a transmitter (18) for generating and transmitting an optical signal and a receiver (20), wherein said receiver (20) comprises a receiver input amplifier (40) at the receiver's input.

Abstract: A system for determining skew comprises an optical transmitter unit adapted to generate an optical output signal with a first plurality of signal components and adapted to feed the optical output signal into an optical output path; an optical receiver unit adapted to receive an optical input signal with a second plurality of signal components from an optical input path; and an optical loopback path adapted to connect the optical output path to the optical input path. The optical loopback path is adapted to couple the first plurality of signal components of the optical output signal at least partly with the second plurality of signal components of the optical input signal. The system further comprises an analysis unit adapted to determine, from the coupled optical input signal, both a first skew pertaining to the optical transmitter unit and a second skew pertaining to the optical receiver unit.

Abstract: The invention discloses a method of amplifying an optical signal, in particular a data signal, transmitted from a first location (A) to a second location (B) via a first transmission link (10a), wherein said optical signal is amplified by means of a transmitter side remote optically pumped amplifiers (ROPA) (18) comprising a gain medium (24), wherein the gain medium (24) of said transmitter side ROPA (18) is pumped by means of transmitter side pump power (20) provided from said first location (A), characterized in that at least a part of said transmitter side pump power (20) is provided by means of light supplied from said first location (A) to said transmitter side ROPA (18) via a portion of a second transmission link (10b) provided for transmitting optical signals from said second location (B) to said first location (A).

Abstract: A system (10) for detecting a level of dirtiness of a filter mat (20) of an airflow cooling system for telecommunications equipment, the system (10) comprising a detector (12) for detecting fluorescent or reflected light backscattered at at least one part in (22) of the filter mat (20) comprising or treated with a fluorescent or reflective material, wherein the detector (12) comprises a light source (12a) for illuminating said at least one part (22) of the filter mat (20) with sampling light, and a photosensor (12b) for detecting fluorescent or reflected light backscattered at said at least one part (22) of the filter mat (20) caused by the illumination thereof with sampling light, wherein the system (10) is configured for inferring the level of dirtiness of the filter mat (20) from the amount of detected fluorescent or reflected light.

Abstract: A method of distinguishing whether a detected change in reflected power in an optical time domain reflectometer (OTDR) measurement carried out in a fiber optic transmission system (16) using an OTDR is caused by a an event causing actual attenuation or a change in a mode field diameter, comprising the steps of emitting a succession of first sampling light pulses of a first wavelength into the fiber optic transmission system (16) while a pumping signal with a second wavelength is emitted into the fiber optic transmission system (16), and measuring a first OTDR trace (34?) resulting from the reflection of the first sampling light pulses in the fiber optic transmission system (16), such that the first sampling light pulses and their reflections interact with the pumping signal via stimulated Raman scattering.

Abstract: Disclosed herein is a method of transmitting a data stream from a first location to a second location through an optical network, as well as a corresponding performance monitoring unit, a transmitting arrangement and a receiving arrangement.

Abstract: A method of distinguishing whether a detected change in reflected power in an optical time domain reflectometer (OTDR) measurement carried out in a fiber optic transmission system (16) using an OTDR is caused by a an event causing actual attenuation or a change in a mode field diameter, comprising the steps of emitting a succession of first sampling light pulses of a first wavelength into the fiber optic transmission system (16) while a pumping signal with a second wavelength is emitted into the fiber optic transmission system (16), and measuring a first OTDR trace (34?) resulting from the reflection of the first sampling light pulses in the fiber optic transmission system (16), such that the first sampling light pulses and their reflections interact with the pumping signal via stimulated Raman scattering.

Abstract: An optical network is suggested, comprising a first set of optical fibers, a multimode multiplexer, a multimode amplifier, a multimode demultiplexer, and a second set of optical fibers, wherein the first set of optical fibers is connected via the multimode multiplexer to the multimode amplifier and wherein the multimode amplifier is connected via the multimode demultiplexer to the second set of optical fibers. Accordingly, an optical network element is provided.