A method to determine the types of optical fibers forming a link of an optical communication network. By scanning a signal's bit error rate at a receiver end, as a function of a pre-dispersion applied to a signal at a transmitter end, local minimums in the curve indicate the presence of amplifiers, and therefore fiber span extremities. By determining the accumulated dispersion at each fiber extremity, a ratio of dispersion per span length can be obtained and the span's coefficient of chromatic dispersion be inferred, thereby identifying the type of fiber. Alternatively, a signal's signal-to-noise ratio can be scanned, instead of its bit error rate. In a typical network, the required instrumentation is pre-existing.

Optical signal to noise ratios that more accurately characterize optical link noise are determined. As noise induced by an optical receiver does not generally vary with an input optical signal power, a power of an incoming optical signal is varied at the receiver. A resulting variation in noise measure represents a variation in link noise and does not include any variation caused by receiver noise, as receiver noise does not generally vary with optical signal power. Thus, the contribution of optical link noise can be discerned from other noise induced by the receiver itself. A more accurate characterization of optical link performance is thus provided.

A method for providing a maximum channel capacity per optical channel in an optical wavelength division multiplexing, WDM, transmission system is described. The WDM transmission system includes transceivers using multiple optical channels in a WDM channel grid to transport optical signals modulated with a modulation format with a signal symbol rate, SR, via an optical transmission link, OTL, along an optical path from a transmitting transceiver to a receiving transceiver. A channel capacity of the optical channel is maximized while a calculated channel margin, CM, is maintained above a preset minimal channel margin value.

A free-space optical (FSO) terminal may include a controller and an alignment sensor. The alignment sensor includes a set of detectors. Each detector generates a signal responsive to receiving electromagnetic radiation at a detection surface. The set of detectors includes an inner set of detectors and an outer set of detectors. The detection surfaces of the inner detectors and the outer detectors may be aligned in a plane. The outer set of detectors surround the inner set of detectors (e.g., in the plane) and have larger detection surfaces than the inner set of detectors. During a tracking mode, the controller is configured to adjust an orientation of the FSO terminal based on signals from the inner set of detectors. During an acquisition mode, the controller is configured to adjust the orientation of the FSO terminal based on signals from the outer set of detectors.

A performance monitor configured to unify at least two different signal-quality estimates into a single performance metric such that a systematic error associated with the performance metric can be approximately constant or smaller than a specified fixed limit over a significantly wider range of data-link conditions than that of a conventional performance metric of similar utility. In an example embodiment, the performance metric can be based on a weighted sum of two different SNR estimates, obtained from an error count of the receiver's FEC decoder and from a constellation scatter plot generated using the receiver's symbol decoder, respectively. Different weights for the weighted sum may be selected for different data-link conditions, e.g., using SNR thresholding, analytical formulas, or pre-computed look-up tables. The performance metric may be supplied to a control entity and considered thereby as a factor in a possible decision to trigger protective switching and/or a transponder-mode change.

A method for establishing a data model and an apparatus, where a network element may create an optical signal group that includes optical signals with different wavelengths. After selecting a first optical signal group and obtaining first data of the first optical signal group, the network element may reflect, based on a first model established based on the first data of the first optical signal group, a noise coefficient and a gain that are obtained after an optical signal in the optical signal group of different wavelength combinations passes through the network element.

Disclosed herein are methods and systems for computing a launch power for an optical node by collecting data for an optical network segment and inputting the collected data and first power spectral density values into a machine learning model which are used to compute a first non-linear interference value. A first generalized-optical signal-to-noise ratio value is computed using the computed first non-linear interference value and amplified spontaneous emission values. At least one second generalized-optical signal-to-noise ratio value is computed using at least one second non-linear interference value, computed using at least one second power spectral density values, and the amplified spontaneous emission values. A highest generalized-optical signal-to-noise ratio value is determined by comparing the first generalized-optical signal-to-noise ratio value and the at least one second generalized-optical signal-to-noise ratio value. A launch power is computed using the power spectral density values associated with the highest generalized-optical signal-to-noise ratio.

In one embodiment, information passing mechanism between the two connected optical transceivers is provided. Within the first optical transceiver, Rx 1 calculates the current condition of the uplink channel and passes this information together with the condition of the downlink channel that it receives from Tx 2 to Tx 1. The Tx 1 uses the downlink channel condition that it receives from the Rx 1 to generate signal with appropriate modulation format, shaping factor, baudrate and coding scheme for maximizing the downlink's capacity. The Tx 1 then transmits this information together with the uplink channel condition received from Rx 1 to Rx 2. The Rx 2 uses the information about the modulation format, baudrate, shaping factor and coding scheme that it receives from Tx 1 for the reception of information-bearing signal. The Rx 2 then calculates the transmission channel condition of the downlink channel and passes this information together with the uplink channel condition that it receives from Tx 1 to Tx 2. The Tx 2 then uses the uplink channel condition that it receives from the Rx 2 to generate signal with optimized modulation format, shaping factor, baudrate and coding scheme for maximizing the uplink's capacity. The information exchange process between the two connected optical transceivers then repeats in an endless loop.

An optical signal processing method, a control unit, an optical transmission unit and a storage medium are disclosed. The optical signal processing method includes: acquiring an OSNR value from an optical receiving unit (S100); acquiring a spectrum shaping adjustment parameter according to the OSNR value (S200); and sending the spectrum shaping adjustment parameter to an optical transmission unit to adjust a filtering parameter of a shaping filter of the optical transmission unit, so that the optical transmission unit adjusts a spectrum waveform of an optical signal by utilizing the shaping filter after adjustment (S300).

A signal processing device processes reception signals of optical signals received by a receiver when the optical signals transmitted from a transmitter are propagated to the receiver via a plurality of paths, and includes: a signal-to-noise ratio calculating unit that calculates signal-to-noise ratios of the optical signals that have been propagated through the respective paths, from propagation distances of the optical signals in the respective paths, intensities of the optical signals transmitted from the transmitter, and intensities of noise with respect to the optical signals transmitted from the transmitter; an amplitude adjusting unit that adjusts amplitudes of the reception signals of the optical signals that have been propagated through the respective paths, using the corresponding signal-to-noise ratios calculated by the signal-to-noise ratio calculating unit; and a signal combining unit that combines the reception signals whose amplitudes have been adjusted by the amplitude adjusting unit.