An optical receiver capable of substantially measuring the phase and amplitude of a received intensity- or amplitude-modulated optical signal by performing digital-signal processing. In an example embodiment, a DSP of the receiver operates to reduce the detrimental effects of relative phase noise between the optical reference oscillator and optical carrier based on an optical pilot present in the received optical signal. The DSP may employ a sequence of digital filters configured to select a signal component that represents a non-vestigial modulation sideband and then perform signal equalization thereon. The signal equalization may include but is not limited to dispersion compensation. In some embodiments, the optical receiver can be a direct-detection optical receiver. In an example embodiment, the optical reference oscillator and optical carrier are generated using two respective independently running lasers that may or may not be co-located.

A receiver is configured to generate a digital signal representative of data conveyed by a communication signal detected at the receiver, and to apply digital signal processing to the digital signal, thereby generating a processed signal. The receiver is further configured to determine a relative noise estimate for the processed signal, and to load an amount of digital noise into the digital signal processing based on a difference between the relative noise estimate and a target. As a result of the digital noise loading, improved stability of at least one control loop in the receiver may be achieved.

An example optical receiving device includes a photodiode to receive an optical signal, where the photodiode is configured to conduct a current that is based on an optical power of the optical signal, and a radio frequency (RF) gain circuitry to generate one or more analog electrical signals based on the current and based on gain provided by the RF gain circuitry. A power detector is configured to receive an analog electrical signal of the one or more analog electrical signals, to detect alternating current (AC) power of the optical signal based on the analog electrical signal, and to output a signal representing the AC power based on the detecting.

The present invention relates to a multi-channel IM-DD optical transceiver comprising at least one transmitter and a receiver, and a method for equalizing input samples at an adjusted sampling phase using a quality parameter linearly proportional to a BER. The data transmission and reception use a single master channel and slave channels, which have a baud rate equal to or lower than the baud rate of the master channel. A reliable and identical clocking of all the channels is obtained through either the receiver clock of the master channel when they are received from a single transmitter or a reference clock whose frequency is higher than the highest clock frequency amongst all the channels when they are received from a combination of transmitters. An enhanced timing recovery circuit is also provided to select optimized finite impulse response filters, calculate filter coefficients and generate the receiver clock of the master channel.

An optical module processes first FEC (Forward Error Correction) encoded data produced by a first FEC encoder. The optical module has a second FEC encoder for further coding a subset of the first FEC encoded data to produce second FEC encoded data. The optical module also has an optical modulator for modulating, based on a combination of the second FEC encoded data and a remaining portion of the first FEC encoded data that is not further coded, an optical signal for transmission over an optical channel. The second FEC encoder is an encoder for an FEC code that has a bit-level trellis representation with a number of states in any section of the bit-level trellis representation being less than or equal to 64 states. In this manner, the second FEC encoder has relatively low complexity (e.g. relatively low transistor count) that can reduce power consumption for the optical module.

An optical receiver includes: a pre-amplifier to convert a current signal into a voltage signal; an LIA to amplify and limit an amplitude of the voltage signal; a transmission line connecting the pre-amplifier with the LIA; an AC coupling capacitor inserted in the middle of the transmission line or at an end of the transmission line; a termination circuit connected with the transmission line, for switching to a first resistance or a second resistance higher than the first resistance in response to a switching signal; and an AC load connected with the transmission line. The AC load is open in a low-frequency range of the voltage signal and having a resistance enabling impedance matching with the pre-amplifier and the transmission line in a high-frequency range of the voltage signal, wherein the termination circuit and the AC load are electrically connected in parallel.

This application provides a receiver optical sub-assembly, a bi-directional optical sub-assembly, and an optical network device to improve anti-electromagnetic crosstalk performance of the receiver optical sub-assembly. The receiver optical sub-assembly includes: a photodiode, a trans-impedance amplifier, and a first filter component. The photodiode is configured to convert an optical signal into an electrical signal, a positive electrode of the photodiode is connected to an input terminal of the trans-impedance amplifier, and a negative electrode of the photodiode is configured to connect to a power supply. The trans-impedance amplifier is configured to amplify the electrical signal output by the photodiode, a power terminal of the trans-impedance amplifier is configured to connect to a power supply, and a first ground terminal of the trans-impedance amplifier is configured to connect to an external ground.

A driver circuit of a PAM-N transmitting device transmits a PAM-N signal via a communication channel, wherein N is greater than 2, and the PAM-N signal has N signal levels corresponding to N symbols. A PAM-N receiving device receives the PAM-N signal. The PAM-N receiving device generates distortion information indicative of a level of distortion corresponding to inequalities in voltage differences between the N signal levels. The PAM-N receiving device transmits to the PAM-N transmitting device the distortion information indicative of the level of the distortion. The PAM-N transmitting device receives the distortion information. The PAM-N transmitting device adjusts one or more drive strength parameters of the driver circuit of the PAM-N transmitting device based on the distortion information.

A receiver apparatus comprises circuitry configured for storing a first sequence of values. At the receiver apparatus, a communications signal is received which conveys a second sequence of values, the second sequence of values being related to the first sequence of values. According to some examples, the second sequence of values is identical to the first sequence of values. At the receiver apparatus, P results are calculated from a cross-correlation of the first sequence of values with at least a portion of a representation of the communications signal, where P is a positive integer. According to some examples, P≥2. An estimate of a phase offset of a continuous clock is calculated as a function of the P results. According to some examples, the function is a non-linear function. The estimate of the clock phase offset may be used to achieve clock recovery at the receiver apparatus.

The present invention is directed to communication methods and systems thereof. In a specific embodiment, a noise cancelation system includes a slicer that processes a data stream generates both PAM symbols and error data. An RIN estimator generates RIN data based on the PAM symbols and the error data. A filter removes non-RIN information from the RIN data. The filtered RIN data includes an offset term and a gain term, which are used to remove RIN noise from the data stream. There are other embodiments as well.