The present invention is directed to data communication system and methods. More specifically, various embodiments of the present invention provide a communication interface that is configured to transfer data at high bandwidth using PAM format(s) over optical communication networks. A feedback mechanism is provided for adjusting the transmission power levels. There are other embodiments as well.

According to an aspect of an embodiment, a method may include receiving a digital data signal at an optical receiver. The method may further include measuring an eye quality of the received digital data signal. In addition, the method may include adjusting a decision threshold of the optical receiver based on the measured eye quality.

An optical receiver includes an APD, a preamplifier, a limiting amplifier, and an upper-level system. The preamplifier includes a core amplifier circuit that amplifies a current signal, an AGC that changes a conversion gain of the core amplifier circuit by adjusting a first adjustment value, a single phase differential conversion circuit that converts a single-phase signal from the core amplifier circuit into a differential signal, an ATC that changes a threshold for use in the single phase differential conversion circuit by adjusting a second adjustment value, and a processing unit that associates the first adjustment value obtained by adjustment by the AGC based on an output of the core amplifier circuit and the second adjustment value obtained by adjustment by the ATC based on the output of the core amplifier circuit with identification information of one of the slave station devices to store them in a storage unit.

A light receiving device that includes a lens that collects a spatial light signal, a sensor array including a plurality of light receivers that receives the spatial light signal collected by the lens, and a reception unit that integrates an electric signal derived from the spatial light signal received by each of the plurality of light receivers and selects a light receiver that receives the spatial light signal. according to a voltage value of the integrated electric signal.

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 on-chip AC coupled receiver with offset calibration. The receiver includes AC coupling circuitry to couple a differential input signal into a coupled differential signal having a first signal and a second signal. The receiver includes a first comparator to generate a first error signal indicative of whether a first reference signal is greater or smaller than a signal derived from the coupled differential signal. The receiver includes a second comparator to generate a second error signal indicative of whether a second reference signal is greater or smaller than the signal derived from the coupled differential signal. The receiver further includes feedback circuitry to adjust a voltage offset between the first signal and the second signal of the coupled differential signal based on the first error signal and the second error signal.

An apparatus comprising a receiver configured to receive a super-symbol comprising a first modulation symbol and a second modulation symbol, wherein the first modulation symbol comprises a first modulation format, and wherein the second modulation symbol comprises a second modulation format, and a processor coupled to the receiver and configured to select, for the first modulation symbol, a first nearest candidate symbol from a first set of candidate symbols associated with the first modulation format, select, for the second modulation symbol, a second nearest candidate symbol independent of the first nearest candidate symbol from a second set of candidate symbols associated with the second modulation format, and determine a soft decision value for a first bit in the super-symbol according to the first nearest candidate symbol and the second nearest candidate symbol.

An optical signal recognition method comprises: initializing a recognition apparatus; acquiring optical source voltage values in an acquisition channel to obtain a group of optical source voltage values; comparing the group of optical source voltage values with a comparison threshold, and converting the group of optical source voltage values into optical data; when the optical data is different from optical data obtained in a previous conversion, continuing to acquire optical source voltage values in the acquisition channel, converting a group of optical source voltage values into optical data, and sequentially storing the optical data in a conversion array; when a preset quantity of optical data in the conversion array is different, deleting optical data stored earliest in the conversion array, continuing to acquire optical data and sequentially storing the optical data in the conversion array; and when all optical data in the conversion array is the same, setting frame data as optical data in the conversion array, and returning the frame data. In the present invention, a synchronization signal is canceled, thereby improving the transmission quality and the transmission speed.

Systems and methods for autonomous signal modulation format identification are disclosed. In an example embodiment of the disclosed technology, a method includes mapping an input signal to Stokes space to determine whether a considered number of three-dimensional clusters value is above or below a predetermined value. The method may include selecting a modulation format from a first set of modulation formats if the considered number of three-dimensional clusters value is above the predetermined value. The method may further include applying higher-order statistics if the considered number of three-dimensional clusters value is below the predetermined value.

An apparatus comprising a receiver configured to receive a super-symbol comprising a first modulation symbol and a second modulation symbol, wherein the first modulation symbol comprises a first modulation format, and wherein the second modulation symbol comprises a second modulation format, and a processor coupled to the receiver and configured to select, for the first modulation symbol, a first nearest candidate symbol from a first set of candidate symbols associated with the first modulation format, select, for the second modulation symbol, a second nearest candidate symbol independent of the first nearest candidate symbol from a second set of candidate symbols associated with the second modulation format, and determine a soft decision value for a first hit in the super-symbol according to the first nearest candidate symbol and the second nearest candidate symbol.