A method is provided for determining an optical signal to noise ratio of a dual polarization optical signal. The method includes: detecting, in the dual polarization optical signal, a modulation signal which modulates, at at least one low amplitude level that is approximately zero and at a high amplitude level, the dual polarization optical signal, and determining the optical signal to noise ratio from a measurement of the power of the modulation signal.

Apparatuses, systems, and methods of communication using visible light communications (VLC) are provided. A system can include a VLC transmitter and a VLC receiver suitable for implementing a diversity combining technique. The diversity combining technique can include equal gain combining, selective best combining, and maximal ratio combining. The VLC transmitter can be a multi-element diversity transmitter and can provide illumination as well as data transfer.

A controller for a front-exciting Raman-amplifier that amplifies an optical signal transmitted from one end of an optical fiber to other end by inputting an excitation light to the one end, the controller includes a memory, and a processor coupled to the memory and configured to acquire communication-related information regarding communication of the optical signal in the optical fiber, when the acquired communication-related information does not indicate the communication of the optical signal, set a Raman gain of the front-exciting Raman amplifier based on a first light intensity of an amplified spontaneous scattered light of the excitation light, and when the acquired communication-related information indicates the communication of the optical signal, set the Raman gain based on a second light intensity of the optical signal output from the optical fiber.

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 detecting defects in a composite structure, such as in an aircraft structure, that includes sending an optical signal down an optical fiber embedded in the composite structure and analyzing the optical signal at a detector. If it is determined that the optical signal is turning on and off or an increase in the bit error rate is occurring at the detector, the composite structure may be delaminating or the composite structure may be somehow damaged. If it is determined that the composite structure is damaged, the optical signal can be sent down a different optical fiber that may not be at a location where the composite structure is damaged, and a continuous beam of light can be sent down the optical fiber that is at the damaged part of the composite structure to determine whether the damage is increasing.

The present disclosure relates to optical communications, and in particular, to a DWDM remote pumping system for improving an OSNR. The system includes remote pumping gain unit, preamplifier, and gain flattening filter sequentially connected. Remote pumping gain unit and preamplifier are cascaded one behind the other as a whole amplifier. Gain flattening filter is disposed at the preamplifier's output end. In the system, remote gain unit and preamplifier which have large impact on the OSNR of the entire system are optimally designed as a whole amplifier. In remote gain unit, gain flattening filter originally disposed between two erbium-doped fiber segments is moved back to preamplifier's output end for significant improvement of gain and noise figures of the remote gain unit while ensuring gain flatness of the entire transmission system, thus effectively improving the entire system's OSNR, improving operation stability and reliability, effectively reducing bit error rate, and facilitating system maintenance.

Systems and methods include, responsive to obtaining measurement data from an optical network and determining viability of a plurality of paths based on Signal-to-Noise Ratio (SNR) and availability of the plurality of paths, providing a User Interface (UI) that displays one or more photonic services and a path viability visualization for each of the one or more photonic services, wherein the path viability visualization, for each photonic service, includes visual elements for available paths of the plurality of paths and an indicator associated with each visual element indicative of path viability; and updating the UI responsive to a change in any of the viability and the availability of the plurality of paths. The steps can further include periodically obtaining the measurement data from the optical network and determining the viability of the plurality of paths.

An optical transmission device includes a reception unit that receives a first signal light and a second signal light, the first and second lights having power levels that respectively correspond to transmission distances and being transmitted; an amplification unit that amplifies the first signal light and the second signal light in accordance with a signal light having a high power level from among the received first signal light and second signal light; and a transmission unit that performs transmission of the amplified first signal light and second signal light.

Embodiments of the present application provide a visible light signal receiving and control method, a control apparatus, and a receiving device. The method comprises: determining a communication performance between a visible light signal receiving device and at least one visible light signal transmit device; and in response to a reduction of the communication performance between the visible light signal receiving device and the at least one visible light signal transmit device, using a first logic pixel unit of an image sensor related to the at least one visible light signal transmit device as at least two second logic pixel units for reading separately when reading inductive charges of the image sensor of the visible light signal receiving device. The method, apparatus, and device of the embodiments of the present application are capable of compensating reduction of a communication performance to some extent by changing the charge readout mode of an image sensor of a visible light signal receiving device, and are more suitable for visible light communications in complicated mobile scenarios.

An optical path for transmission of data from a source node to a destination node comprises an optical channel for parallel transmission of non overlapping carrier frequencies. The frequency separation of the carriers is lower than the baud rate. The optical path is configured by (a) determining a path OSNR (OSNR.sub.p ); (b) selecting a carrier bandwidth (BW) so that the channel bandwidth (BW.sub.T ) is less than or equal to a maximum path bandwidth available for transmission, wherein BW.sub.T≈BW.Math.C, wherein C is the number of carrier frequencies; (c) selecting a FEC code having a minimum overhead requirement; (d) determining a channel OSNR (OSNR.sub.T ) based on the currently selected BW and FEC code; (e) in response to determining that OSNR.sub.T is not less than or equal to OSNR.sub.p, reselecting new codes having increasing overhead requirements until OSNR.sub.T is less than OSNR.sub.p, and if this is not possible increasing BW.sub.T and returning to step (c); (h) configuring the path for transmission based on the finally selected BW.sub.Tand FEC code.