A method for assigning a network path after receiving a connection request to connect a first node with a second node of a network. The method including evaluating a network utilization parameter of the network, such as a network load or blocking probability, at that point in time. If the network utilization parameter is below a minimum threshold level, the method includes carrying out the steps of identifying a set of n network paths through the network that connect the first node with the second node and are absent non-linear links, performing network path selection by selecting p network paths from the set of n network paths that have the best linear OSNR, and, selecting a network path from the set of p network paths that balances the wavelength utilization between the first node and the second node of a network.

Systems and methods for determining margin in an optical network include changing powers of signals from one or more transmitters; measuring noise at one or more receivers each communicatively coupled to the one or more transmitters; and determining margin between the one or more transmitters and the one or more receivers based on the associated measured noise. The changing, the measuring, and the determining are performed in-service while the one or more transmitters are each transmitting data-bearing signals.

The present disclosure discloses a data transmission method, an apparatus, and a system. The method includes: receiving, by a mode multiplexer from an input port, a first optical signal transmitted by an optical line terminal; converting, according to a correspondence between an input port of an optical signal and a mode of the optical signal, the received first optical signal into a second optical signal in a mode corresponding to the input port; and multiplexing the second optical signal obtained by means of conversion to a few-mode optical fiber for transmission. This increases transmission capacity of a single optical fiber and implements fast expansion of the transmission capacity, thereby improving total bandwidth utilization of a system.

A network control apparatus includes a processor. The processor calculates a first OSNR corresponding to an allowable limit BER from an OSNR yield strength curve of a transmission end in a node of a transmission end. The processor acquires a reception BER of a second node of a reception end, and calculates a second OSNR corresponding to the reception BER from the OSNR yield strength curve of the transmission end. The processor calculates a first noise intensity corresponding to the allowable limit BER from the first OSNR. The processor calculates a second noise intensity corresponding to the reception BER from the second OSNR. The processor calculates a noise intensity margin, based on the first noise intensity and the second noise intensity.

A first transmission apparatus includes a first transmitter and a first receiver. The first transmission apparatus transmits a first optical signal to a second transmission apparatus, which is generated by modulating first light output by a first light source. The first receiver coherently receives a second optical signal transmitted by a second transmission apparatus using the first light output by the first light source. The second transmission apparatus includes a second transmitter, a second receiver, and a controller. The second transmitter transmits the second optical signal to the first transmission apparatus, which is generated by modulating second light output by a second light source. The second receiver coherently receives the first optical signal transmitted by the first transmission apparatus using the second light output by the second light source. The controller controls a wavelength of the second light to be output by the second light source.

A method and apparatus for determining in-band OSNR in optical information signals, e.g. in polarization-multiplexed QPSK and higher-order M-ary QAM signals, are disclosed. A correlation measurement of the signal amplitude or power at two distinct optical frequencies of the signal may be used to determine the in-band optical noise in the signal. A measurement of the signal power may be used to determine the OSNR based on the determined in-band noise.

Various embodiments for regulating link speed for performance enhancement and port diagnosis are provided. In response to identifying an amount of errors in a communications link above a predetermined threshold, an applicable transmission speed is selectively reduced. If errors identified at the reduced transmission speed are found to decrease, a communications port incorporating the communications link is flagged as potentially dirty, and if the errors identified at the reduced transmission speed are found to remain constant, the communications port is flagged as potentially bad.

Length metrology apparatuses and methods are disclosed for measuring both specular and non-specular surfaces with high accuracy and precision, and with suppressed phase induced distance errors. In one embodiment, a system includes a laser source exhibiting a first and second laser outputs with optical frequencies that are modulated linearly over large frequency ranges. The system further includes calibration and signal processing portions configured to determine a calibrated distance to at least one sample.

An optical fiber cable of a mobile fronthaul system based on a radio over fiber (RoF), which includes a control apparatus for monitoring an analog optical link according to an exemplary embodiment, may be monitored. The monitoring control apparatus may include an optical signal monitor to monitor an optical signal passing through an optical fiber cable, and a system controller to control the optical signal based on a result of the monitoring. The optical signal monitor may calculate an average optical power, carrier-to-noise ratio (CNR), and a size of a nonlinear component from an electrical signal, which has been acquired from the optical signal. Then, the optical signal monitor may control the calculated average optical power, CNR, and nonlinear component.

The disclosed systems and methods for improving a launch power in an optical link. The improvement of launch power in the optical link is based on: i) selecting an optical span from one or more optical spans within the optical link; ii) applying a power dither to a plurality of the optical signals propagating in the selected optical span; iii) selecting an optical signal from the plurality of the optical signals to which the power dither is applied; iv) correlating the power dither with a performance parameter of the selected optical signal; and v) based on the correlation, adjusting the launch power of a first optical amplifier in the selected optical span to minimize the correlation to approximately equal to zero.