Embodiments include techniques for transmitting and receiving radio frequency (RF) signals, where the techniques for generating, via a digital analog converter (DAC), a frequency signal, and filtering the frequency signal to produce a first filtered signal and a second filtered signal. The techniques also include transmitting the second filtered signal to a device under test, and filtering the second filtered signal into a sub-signal having one or more components. The techniques include mixing the first filtered signal with the sub-signal to produce a first mixed signal, subsequently mixing the first mixed signal with an output signal received from the device under test to produce a second mixed signal, and converting the second mixed signal for analysis.

Systems and methods are provided for enabling lower-bandwidth hardware components to support higher data rates. In particular, aspects of the disclosed systems and methods use Raised Cosine pulse shaping in short-reach links to band limit the signal spectra and thereby enable existing, such lower-bandwidth components to support higher data rates.

Various example embodiments relate to an apparatus and method for nonlinear equalization based on an absolute operation, and may be configured to generate coefficients and compensate for nonlinear distortions by using an absolute operation for an input signal based the coefficients.

An optical signal modulated with a stream of symbols comprising a sequence of training symbols is received at a receiver. First equalizer circuitry calculates and applies first coefficients to digital signals representative of the optical signal, thereby resulting in first compensated signals. Second equalizer circuitry calculates second coefficients based on a correlation between the first compensated signals and digital signals representative of the sequence of training symbols and applies the second coefficients to the first compensated signals, thereby resulting in second compensated signals. Third equalizer circuitry calculates and applies third coefficients to the second compensated signals, thereby resulting in third compensated signals. The first, second, and third coefficients compensate for impairments in the optical signal varying at respective first, second, and third rates, where the third rate is higher than the first rate and lower than the second rate.

An echo cancellation method includes steps of (a) extracting phase-distortion estimates, (b) reconstructing an echo signal, (c) generating a clean signal, and (d) producing a primary signal. Step (a) includes extracting, from a first phase signal, a plurality of phase-distortion estimates, the first phase signal having been estimated from an echo-corrupted signal received at a first coherent transceiver of a coherent optical network. Step (b) includes reconstructing an echo signal from the plurality of phase-distortion estimates and a transmitted signal transmitted by the first coherent transceiver. Step (c) includes generating a clean signal as a difference between the reconstructed echo signal and the first phase signal. Step (d) includes producing a primary signal by mapping each of a plurality of clean-phase estimates of the clean signal to one of a plurality of constellation symbols associated with a modulation scheme of the primary signal.

A circuit and method for mitigating multi-path interference in direct detection optical systems is provided. Samples of an optical signal having a pulse amplitude modulated (PAM) E-field are processed by generating a PAM level for each sample. For each sample, the sample is subtracted from the respective PAM level to generate a corresponding error sample. The error samples are lowpass filtered to produce estimates of multi-path interference (MPI). For each sample, one of the estimates of MPI is combined with the sample to produce an interference-mitigated sample.

A signal receiving apparatus includes at least one signal separating apparatus that separates a specific signal from a plurality of received signals. Each of the at least one signal separating apparatus includes a spatial filtering unit that separates at least one equalized signal and a decision signal outputting unit that generates a first decision signal by deciding the equalized signal and outputs the generated first decision signal. The spatial filtering unit separates the at least one equalized signal by multiplying at least the plurality of received signals among the plurality of received signals and either the first decision signal output from the decision signal outputting unit or a second decision signal output from another signal separating apparatus by predetermined weighting coefficients.

A communication interface comprising a host with non-linear equalizers configured to perform non-linear equalization. Also part of the interface is a host to optic module channel electrically connecting the host to an optic module and the optic module. The optic module comprises a transmitter and a receiver. The transmitter includes a linear equalizer and an electrical to optical module configured to convert the equalized signal from the driver to an optical signal, and transmit the optical signal over a fiber optic cable, such that the transmitter does not perform non-linear processing. The receiver includes a photodetector, configured to convert the received optic signal to a received electrical signal, and a linear amplifier configured to perform linear amplification on the received electrical signal. A driver sends the amplified received signal over an optic module to host channel, such that the receive does not perform non-linear processing.

The present disclosure provides a non-linear receiver, an asymmetric decision feedback equalization circuit and method, including: converting an optical signal emitted by a laser device into an electrical signal; obtaining a compensation amplitude of a current data in the electrical signal by obtaining an actual amplitude of the current data, and compensating the current data based on a logic value of k prior data of the current data and a feedback coefficient corresponding to the prior data; comparing the compensation amplitude of the current data with a decision threshold to determine the logic value of the current data; the feedback coefficient is an absolute value of an influence amount of the prior data on an amplitude of the current data, and k is a positive integer. The present disclosure can overcome the bit error problem of the receiver and reduce jitter of the clock recovered by the clock recovery circuit.

Systems and methods are provided for enabling lower-bandwidth hardware components to support higher data rates. In particular, aspects of the disclosed systems and methods use Raised Cosine pulse shaping in short-reach links to band limit the signal spectra and thereby enable existing, such lower-bandwidth components to support higher data rates.