An optical transmission apparatus (100) generates a second bit sequence B by encoding a first bit sequence b having forward error correction coding performed on a transmission bit sequence, maps the second bit sequence to a transmission symbol signal, and transmits an optical modulated signal generated by modulating an optical carrier wave into the transmission symbol signal. A symbol output unit (2020) generates a received symbol signal by demodulating an optical modulated signal received by an optical reception apparatus (2000). A first computation unit (2040) computes LLR(Bi) which is a log-likelihood ratio (LLR) of each bit Bi of the second bit sequence, using the received symbol signal. A second computation unit (2060) computes a log-likelihood ratio LLR(bi) of each bit bi of the first bit sequence from the LLR(Bi). A correspondence relationship between each bit of the first bit sequence and each bit of the second bit sequence is used in this computation. A decoding unit (2080) decodes the transmission bit sequence using the LLR(bi).

An example optical receiver may have an optical receiver front-end, four slicers, and a logic block. The optical receiver front-end may include a transimpedance amplifier to convert a photodiode output signal to a voltage signal. Three of the slicers may be data slicers, and one of the slicers may be an edge slicer. The slicers may each: shift the voltage signal based on an offset voltage set for the respective slicer, determine whether the shifted voltage signal is greater than a threshold value and generate a number of comparison signals based on the determining, and generate multiple digital signals by demuxing the comparison signals. The logic block may perform PAM-4 to binary decoding based on the data signals output by the data slicers and clock-and-data-recovery based on the digital signals output by the edge slicer.

A system and method for controlling optical receiver operation in response to a received optic signal power level that includes providing an optic signal receiver having operation determined by one or more system settings. During operation, the optic signal is received and converted to an electrical signal. The electrical signal is evaluated to determine a power level of the electrical signal. Responsive to the power level of the electrical signal exceeding a first predetermined threshold, adjusting a first system setting and responsive to the power level of the received electrical signal decreasing below a second predetermined threshold, adjusting the first system setting. Then, responsive to the power level of the received electrical signal exceeding a third predetermined threshold, adjusting a second system setting and responsive to the power level of the received electrical signal decreasing below a fourth predetermined threshold, adjusting the second system setting.

A modulated light receiver includes a photo-sensitive element, an electromagnetic interference (EMI) detection circuit, and a decision-making controller. The photo-sensitive element is configured to generate an electrical signal in response to modulated light. The electromagnetic interference (EMI) detection circuit is configured to generate an electrical signal in response to EMI. The decision-making controller is electrically coupled to the photo-sensitive element and the EMI detection circuit, wherein the decision-making controller generates an output based on the inputs received from the photo-sensitive element and the EMI detection circuit.

The present disclosure includes a photodetector element (11) that converts an optical signal into an electric current signal; a transimpedance amplifier (12a) that converts the electric current signal into a voltage signal; a differential amplifier (12d) that converts the voltage signal into a differential signal, by performing differential amplification of a difference between the voltage signal and a threshold voltage; an LOS detection circuit that detects a no-signal section of the optical signal; and an MCU that repeatedly executes offset cancellation processing, the offset cancellation processing including threshold voltage change processing in which the threshold voltage is changed such that an offset voltage of the differential signal is reduced, the MCU 13 skipping the threshold voltage change processing in the no-signal section.

An optical communication system includes a transmission side system for multi-level pulse amplitude modulation (PAM) and a corresponding receiver side system, where the transmission side comprises a laser source providing an optical beam, a signal source of electrical signals to be modulated onto the optical beam, and a modulator coupled to the laser source and the signal source to modulate the electrical signals onto the optical beam using amplitude modulation and at least four signal levels, wherein the at least four signal levels are non-uniformly distributed. The receiver side includes a corresponding equalizer which is implemented as a filter of the form f.sub.1y+f.sub.2y.sup.2+f.sub.0, where y is the incoming signal and the parameters f.sub.0, f.sub.1 and f.sub.2 are obtained using an adaptive filter.

An optical receiver to receive a multilevel modulation signal in which a value of transmission data is assigned to plural signal levels, the optical receiver including a clock generator to generate a recovered clock signal from the multilevel modulation signal when the clock generator detects that a signal level of the multilevel modulation signal transitions between two median levels of the signal levels, and a data identifier to identify a value of the transmission data by using the generated recovered clock signal and the multilevel modulation signal.

A modulated light receiver includes a photo-sensitive element, an electromagnetic interference (EMI) detection circuit, and a decision-making controller. The photo-sensitive element is configured to generate an electrical signal in response to modulated light. The electromagnetic interference (EMI) detection circuit is configured to generate an electrical signal in response to EMI. The decision-making controller is electrically coupled to the photo-sensitive element and the EMI detection circuit, wherein the decision-making controller generates an output based on the inputs received from the photo-sensitive element and the EMI detection circuit.

A synchronized pattern sequence system including a processor and a timing receiver configured to receive a time reference signal to set a time of the electronic device. The system further includes sequence receiver configured to receive a sequence pattern and a timing for presenting the sequence pattern and a pattern indicator configured to present the sequence pattern. The system also has a memory and machine-readable code stored in the memory. The machine-readable code is configured to cause the processor to direct the pattern indicator to present the sequence pattern as a recognizable pattern according to the received timing in synchronization with the sequence pattern presented on at least one other electronic device.

A waveform matching based optical digital signal receiving device sequentially comprises an optical arbitrary waveform generator unit, an electro-optic modulator unit, an opto-electric converter unit, an electric filter unit, a sampling and judging module, a digital signal processing unit and a bit-timing extracting module. Accordingly, signal matched filtering, sampling and judgment can be effectively carried out in the optical domain, and the influence of noises on signal reception can be eliminated to the maximum extent, thereby achieving accurate detection and reception of signals. Meanwhile, compared with a conventional electric receiving device, the digital signal receiving device provided by the present invention breaks the limitation of electronic bottleneck, and greatly improves the bandwidth of signal reception, which allows digital signal reception at a higher speed.