Embodiments may provide a way of communicating via an electromagnetic radiator, or light source, that can be amplitude modulated such as light emitting diode (LED) lighting and receivers or detectors that can determine data from light received from the amplitude modulated electromagnetic radiator. Some embodiments may provide a method of transmitting/encoding data via modulated LED lighting and other embodiments may provide receiving/decoding data from the modulated LED lighting by means of a device with a low sampling frequency such as a relatively inexpensive camera (as might be found in a smart phone). Some embodiments are intended for indoor navigation via photogrammetry (i.e., image processing) using self-identifying LED light anchors. In many embodiments, the data signal may be communicated via the light source at amplitude modulating frequencies such that the resulting flicker is not perceivable to the human eye.

In one example, an apparatus includes an offset tunable edge slicer having an input to receive a pulse amplitude modulation signal. The offset tunable edge slicer also has a plurality of possible offset settings corresponding to a plurality of different reference voltages of the offset tunable edge slicer. A multiplexer has an output coupled to the input of the offset tunable edge slicer and an input to receive a control signal that selects one of the plurality of possible offset settings for the offset tunable edge slicer. A phase detector has an input coupled to an output of the offset tunable edge slicer.

A digital signal processor which performs digital signal processing of a digital signal includes a statistical analysis method which calculates a moving average and a standard deviation from the digital signal, performs statistical decision deciding whether or not the digital signal is within a predetermined range obtained from the moving average and the standard deviation, and corrects the digital signal outside the range within the range. Statistical analysis of the digital signal is performed, thereby suppressing transient changes without increasing the number of times of averaging during the digital signal processing.

Systems, devices and techniques for receiving a signal comprising a quadrature duobinary modulated signal include performing channel equalization of the received signal using a constant multi-modulus to obtain a set of channel estimation coefficients and a stream of symbols, partitioning, based on modulus, the stream of symbols into three partitions, estimating carrier frequency based on the partitioned stream of symbols, recovering a phase of the signal using a maximum likelihood algorithm, and decoding the partitioned stream of symbols to recover data.

Upon receipt of a coherent optical signal that includes a training signal generated using a code sequence constituted by multi-value phase modulation symbols, in which a deviation angle of a vector average of a one-symbol delay differential component of a signal generated on the basis of the code sequence has a prescribed angle and a modulation phase difference between adjacent symbols has a fixed, repeated pattern, a reception training signal corresponding to a training code sequence for frequency offset estimation is detected within a reception signal acquired by converting the received coherent optical signal into an electric signal, a plurality of delay differential components are calculated on the basis of the detected reception training signal and at least two delay signals of the reception training signal, each delay signal having a different number of delay symbols, and an averaged frequency offset amount is calculated using the calculated plurality of delay differential components.

A subchannel encoding device is configured to include: a probability distribution shaping-encoding unit for dividing M×N (M is an integer of two or more, and N is an integer of one or more) subchannels into N groups, shaping a probability distribution of transmission modulation symbols of each group on the basis of signal-to-noise ratios of the M×N subchannels, and converting an information bit string into a shaped bit string corresponding to the probability distribution of the transmission modulation symbols of each group; a subchannel signal generating unit for generating each subchannel signal in the M×N subchannels from the shaped bit string; and a signal multiplexing unit for multiplexing the M×N subchannel signals generated by the subchannel signal generating unit to generate a subchannel multiplexed signal.

Upon receipt of a coherent optical signal that includes a training signal generated using a code sequence constituted by multi-value phase modulation symbols, in which a deviation angle of a vector average of a one-symbol delay differential component of a signal generated on the basis of the code sequence has a prescribed angle and a modulation phase difference between adjacent symbols has a fixed, repeated pattern, a reception training signal corresponding to a training code sequence for frequency offset estimation is detected within a reception signal acquired by converting the received coherent optical signal into an electric signal, a plurality of delay differential components are calculated on the basis of the detected reception training signal and at least two delay signals of the reception training signal, each delay signal having a different number of delay symbols, and an averaged frequency offset amount is calculated using the calculated plurality of delay differential components.

A subchannel encoding device is configured to include: a probability distribution shaping-encoding unit for dividing M×N (M is an integer of two or more, and N is an integer of one or more) subchannels into N groups, shaping a probability distribution of transmission modulation symbols of each group on the basis of signal-to-noise ratios of the M×N subchannels, and converting an information bit string into a shaped bit string corresponding to the probability distribution of the transmission modulation symbols of each group; a subchannel signal generating unit for generating each subchannel signal in the M×N subchannels from the shaped bit string; and a signal multiplexing unit for multiplexing the M×N subchannel signals generated by the subchannel signal generating unit to generate a subchannel multiplexed signal.

An optical communication system is configured to transmit and receive at least four multiplexed, differently-polarized, optically-transmitted signals. Each signal is associated with a predefined state of polarization. An optical transmitter is configured to transmit multiplexed, differently polarized, optically transmitted signals. An optical receiver is configured to receive the optically transmitted signals. The system includes a multi-polarization analyzer circuit configured to obtain an analyzed signal for each of the polarized signals in Stokes space. The analyzer circuit is configured to determine if the multiplexed signal has been transformed by extreme polarization-dependent loss (PDL), the receiver correcting for the extreme polarization-dependent loss.

A power pack for a seat-related supply of power, such as an airplane seat, to an electrical unit having an interface for outputting status information. The interface is configured to provide an optical output of the status information. A method for wirelessly reading out status information of the power pack includes the steps of collecting status information, optically transmitting the collected status information, receiving the collected status information with a mobile receive device, and representing the collected status information on the mobile receive device.