A method of messaging with light is implemented by a light fixture. The method includes: timing and recording a switch-on period, and recording an operation mode of the light fixture during receipt of the electrical power; and operating in a messaging mode the next time the light fixture receives electrical power upon determining that the recorded operation mode is a lighting mode and that the recorded switch-on period is within a predetermined range of time period. In the messaging mode, the light fixture controls a light emitting device to send a binary message by operating in a sequence composed at least of a first brightness state and/or a second brightness state.

An optical wireless transmission system 10 includes a transmission device including at least one memory storing instructions, and at least one processor configured to execute the instructions to; generate a plurality of digital outphasing signals; orthogonally modulate the digital outphasing signals at an intermediate frequency; and set an intermediate frequency for satisfying a specified signal-to-distortion power ratio based on a sampling frequency, wherein the digital outphasing signals are orthogonally modulated at the intermediate frequency; a hardware optical fiber module configured to convert orthogonally modulated digital electrical signals into optical signals, transmit the optical signals through an optical fiber, and convert the optical signals into digital electrical signals; and a remote unit configured to combine the digital electrical signals transmitted by the hardware optical fiber module, and transmit a combined signal as a radio signal.

A probe generator includes: a first demultiplexer configured to branch a first optical signal having a first wavelength into at least two first polarized optical signals; a first adjustor configured to adjust the first polarized optical signals such that the first polarized optical signals have the same polarization direction and to combine the adjusted first polarized optical signals into a second optical signal; a first modulator configured to branch the second optical signal into at least two first split optical signals and to intensity-modulate each of the first split optical signals with first pilot signals; a second adjustor configured to adjust the first split optical signals intensity-modulated by the first modulator such that the intensity-modulated first split optical signals have different polarization directions; and an output unit configured to combine the first split optical signals adjusted by the second adjustor to generate a probe optical signal to be output.

The invention provides a method for nonlinear compensation of coherent high-capacity high-order QAM system, including: deploying an OPC on an intermediate link of communication between a transmitter and receiver, and performing phase conjugation on a transmitted signal based on the OPC to generate idler; performing phase recovery on a compensated signal at the receiver to obtain a constellation diagram, simulating a nonlinear function relationship between a transmitted signal and a received signal by using a trained and learned CVDNN, and performing nonlinear compensation on the constellation diagram to obtain the compensated constellation diagram; and calculating a Q-factor based on the compensated constellation diagram, and evaluating communication performance by the Q-factor. Nonlinear compensation is performed on a transmitted signal by using an OPC+CVDNN method to equalize nonlinear degradation of an optical fiber in a WDM coherent optical communication system.

An apparatus includes a plurality of VCSELs, a master laser, one or more electrical drivers, and an optical combiner. The master laser is configured to transmit laser light to the VCSELs to optically lock wavelengths of the VCSELs. The one or more electrical drivers are connected to directly electrically modulate the VCSELs in a manner responsive to one or more digital data stream. The optical combiner is configured to combine light received from, at least, a pair of the VCSELs into an optical carrier with a substantially phase digital data modulation.

Systems and methods for controlling laser modulation in burst communications. In a start-up phase, a drive circuitry sequentially applies first and second drive currents to a laser diode such that it produces a first and second optical output, respectively. A compensating current source coupled to the laser diode provides a current related to the first and second drive currents to maintain a combined current flowing through an impedance connected to the laser diode at a substantially constant level during the start-up phase. An optical sensor measures the first and second optical outputs, and a controller uses values of the first and second drive currents, the outputs from the optical sensor, and at least one supplied input value to provide control values for the drive circuitry for controlling operating current of the laser diode during a subsequent operating phase, wherein information is transmitted in at least one burst.

Methods in an optical receiver, for decoding a received M-level pulse-amplitude-modulated, PAM-M, optical signal. An example method comprises, for a first interval, decoding (510) the received PAM-M optical signal using a standard PAM-M decoder with M-1 thresholds, using first sampling times, to obtain a first set of decoded bits, and decoding (520) the received PAM-M optical signal using a duobinary decoder with 2M-2 thresholds, at second sampling times offset from the first sampling times, to obtain second set of decoded bits. The method further comprises calculating (530) first and second error metrics corresponding to the first and second sets of decoded bits, respectively, and selecting (540) the standard PAM-M decoder or the duobinary decoder for subsequent decoding of the received PAM-M optical signal, based on the first and second error metrics.

A fiber optic light intensity encryption method is provided. The method includes determining light intensities associated with multi-frequency light pulses emitted by a laser transmitter apparatus in response to an encryptions process. An encryption type for application of an encryption algorithm to each light intensity is determined and a first light intensity associated with a first light pulse is selected. Data indicating results of the random selection is transmitted to the laser transmitter apparatus and an initial security key is transmitted over a signaling channel of the laser transmitter apparatus. The signaling channel is secured based on the initial security key resulting in a secure signaling channel. In response, a secure bundle comprising said the secure signaling channel and an additional group of channels is generated and the data is transmitted via the secure bundle.

A method, system, and apparatus enabled to selectively choose a baud rate for communication of optical data using a modem enabled to operate with an optical signal modulated at plurality of finely tuned baud rates.

Systems and methods for constellation shaping using low rate loss bit-level distribution matchers include receiving blocks of input bits and, for each input block of a predetermined size, assigning a respective codeword of a predetermined output block size. The number of bits of a given bit value in the codeword is dependent on a predetermined target probability distribution. A one-to-one mapping exists between each possible combination of input bits and a codeword for input blocks containing the combination. Some codewords include a number of bits having the given bit value that is different than the predetermined target probability distribution, but an average number of bits having the given bit value in the available codewords meets the predetermined target probability distribution. The disclosed methods result in more available codewords and a lower rate loss than in bit-level distribution matchers with a constant modulus, while achieving similar shaping.