US 2020/0028592 A1 · ADAPTIVE DIGITAL FILTERING IN AN OPTICAL RECEIVER

Abstract

A self-coherent optical data receiver configured to use direct detection of optical signals that is compatible with full (amplitude/phase) electric-field reconstruction. To enable the latter, the direct-detected optical signal includes CW light whose carrier frequency is spectrally aligned with a roll-off edge of the data-modulated portion of the signal. In an example embodiment, the receiver may employ two digital filters placed upstream and downstream, respectively, of the field-reconstruction circuit. The upstream filter is configurable to at least partially cancel the effects of SSBI caused by the direct detection. The downstream filter can be configured to perform electronic dispersion compensation and/or electronic polarization demultiplexing. In different embodiments, a filter controller may operate to adaptively change the filter coefficients of the upstream filter based on different signals generated within the digital receive chain. For example, the filter controller can use either input or output of the downstream filter for this purpose.

Claims20

Dependent claims

An apparatus, comprising an analog front end and a digital signal processor;

wherein the analog front end comprises a photodetector configured to convert an optical input signal into an electrical signal proportional to an optical power of the optical input signal;
wherein the digital signal processor comprises a first digital filter and a field-reconstruction circuit, the first digital filter being configured to generate a first filtered digital signal in response to the electrical signal, the field-reconstruction circuit being configured to estimate at least a phase of the optical input signal in response to the first filtered digital signal;
wherein the first digital filter is configurable to digitally filter a digital representation of the electrical signal to remove therefrom at least some signal distortions imposed by the analog front end;
and
wherein the field-reconstruction circuit is configured to use a Kramers-Kronig algorithm to estimate said at least a phase of the optical input signal based on the first filtered digital signal.

2 more elements

Dependencies are inferred from the claim text.

Adaptive digital filtering in an optical receiver

Life of this patent

Adaptive digital filtering in an optical receiver

Life of this patent

Abstract

Claims20