A direct-detection optical data receiver capable of low-latency SSBI cancellation using one or more FIR filters in the chain of digital signal processing thereof. In an example embodiment, a DSP of the receiver may have first and second serially connected FIR filters whose filter coefficients are updated based on a same feedback signal. An SSBI-cancellation circuit of the DSP is configured to estimate the SSBI by summing a scaled square of the filtered signal generated by the first FIR filter and a scaled square of the filtered signal generated by the second FIR filter. In some embodiments, the SSBI-cancellation circuit may have two or more serially connected stages, each of which incrementally improves the accuracy of the SSBI estimate. In some embodiments, the need for dedicated and/or specialized filter-calibration procedures may beneficially be circumvented.

There are provided an optical transmission apparatus that subjects a transmission signal including a plurality of sequences to Hadamard transform to obtain a signal in which a predetermined delay is added to one of the sequences, optically modulates the obtained signal, and transmits the modulated signal, and an optical reception apparatus that demodulates a reception signal received from the optical transmission apparatus by subjecting the reception signal to adaptive equalization processing with a predetermined number of taps. The optical reception apparatus includes: an adaptive equalization processing unit that subjects the reception signal to adaptive equalization processing of wavelength distortion compensation with a number of taps obtained by subtracting a number in accordance with the delay from the predetermined number of taps; a delay compensation unit that subjects the reception signal subjected to the wavelength distortion compensation to delay compensation in accordance with the delay; and an inverse Hadamard transform unit that subjects the reception signal subjected to the delay compensation to inverse Hadamard transform.

Presented herein are methodologies for using legacy optical fiber for 10 Gigabit Ethernet or higher data rates. The methodology includes obtaining an electrical signal derived from optical-to-electrical conversion of an optical signal that was transmitted over, and received from, an optical fiber; and applying an equalization process to the electrical signal, wherein the equalization process is of a type that is designed to equalize received signals that were transmitted via a copper cable.

High-performance ultra-wideband Phased Array Antennas (PAA) are disclosed, having unique capabilities, enabled through photonic integrated circuits and novel optical architectures. Unique capabilities for PAA systems are enabled by photonic integration and ultra-low-loss waveguides. Novel aspects include optical multiplexing combining wavelength division multiplexing and/or a novel extension to array photodetectors, providing the capability to combine many RF photonic signals with very low loss. Architectures include tunable optical up-conversion and down-conversion systems, moving a chosen frequency band between baseband and a high RF frequency band with high dynamic range. Simultaneous multi-channel RF beamforming is achieved through power combining/splitting of optical signals.

The present disclosure relates to an apparatus and method of processing a digital signal, wherein an input signal is transformed into the frequency domain by applying a fast Fourier transformation (FFT) processing to obtain a transformed input signal. Positive and negative frequency components of the transformed input signal are separated and respective ones of the separated positive and negative frequency components are separately processed by respective digital filtering to obtain filtered frequency components. The filtered frequency components are combined in the frequency domain using a down-sampling operation for down-sampling the filtered frequency components from an input number of samples per symbol to a different output number of samples per symbol, and the combined output components are converted into the time domain by applying an IFFT processing.

A signal processing device included in an optical reception device configured to receive a burst optical signal transmitted by one of a plurality of optical transmission devices, includes a symbol timing detecting unit configured to detect a symbol timing based on sample signals obtained by oversampling the burst optical signal converted into an electric signal with a sampling rate higher than a symbol rate, an adaptive equalization filter unit configured to perform an equalization process on the sample signals, and a timing matching unit configured to match timing such that, when the adaptive equalization filter unit takes in the sample signals, one of the taken-in sample signals corresponding to the symbol timing is given to a tap of which a tap coefficient has a maximum value among taps included in the adaptive equalization filter unit.

Embodiments of this application disclose a board, an optical module, a MAC chip, a DSP, and an information processing method. The board in the embodiments of this application includes a media access control (MAC) chip, a digital signal processor (DSP), and an equalizer. The MAC chip is configured to send first information to the DSP at an optical network unit (ONU) online stage, where the first information includes a first ONU identifier. The DSP is configured to receive the first information, and determine a first reference equalization parameter, where the first reference equalization parameter is related to the first ONU identifier. The DSP is further configured to set an equalization parameter of the equalizer to the first reference equalization parameter.

System and method of adapting thresholds for constellation selection based on statistic distributions of received data symbols. To determine an adapted threshold, an expected ratio of received symbols with values in a certain range is preset based on an expected statistic distribution of data symbols across the multiple constellations. A first and a second ratios are defined based on the expected ratio, the first ratio being the expected ratio minus an error ratio and the second ratio being the expected ratio plus the error ratio. A first value is determined which makes the received symbols in a firs range to constitute the first ratio of a set of slicer inputs. A second value is determined which makes the received symbols in the second range to constitute the second ratio of a set of slicer outputs. The adapted threshold is then obtained based on the first and the second value.

An illustrative receiver includes: a decision element that derives symbol decisions from a slicer input signal; an equalizer that converts a receive signal into the slicer input signal; a summer that combines the symbol decisions with the slicer input signal to produce an error signal; and a level finder that operates on said signals to determine thresholds at which each signal has a given probability of exceeding the threshold. One illustrative level finder circuit includes: a gated comparator and an asymmetric accumulator. The gated comparator asserts a first or a second gated output signal to indicate when an input signal exceeds or falls below a threshold with a programmable condition being met. The asymmetric accumulator adapts the threshold using up steps for assertions of the first gated output signal and down steps for assertions of the second gated output signal, with the up-step size being different than the down-step size.

Lateral and vertical microstructure enhanced photodetectors and avalanche photodetectors are monolithically integrated with CMOS/BiCMOS ASICs and can also be integrated with laser devices using fluidic assembly techniques. Photodetectors can be configured in a vertical PIN arrangement or lateral metal-semiconductor-metal arrangement where electrodes are in an inter-digitated pattern. Microstructures, such as holes and protrusions, can improve quantum efficiency in silicon, germanium and III-V materials and can also reduce avalanche voltages for avalanche photodiodes. Applications include optical communications within and between datacenters, telecommunications, LIDAR, and free space data communication.