US 10,833,769 B1Granted

Coherent optical receiver using single-ended photodiodes

AssigneeNokia Solutions and Networks Oy

InventorThai Son Le

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Abstract

A PDM-capable coherent optical receiver can be implemented using four high-bandwidth photodiodes connected in a single-ended electrical configuration. The SSBI present in the electrical output of the single-ended photodiodes is effectively canceled in the receiver DSP based on measurements of average optical power of the optical data and local-oscillator signals. In various embodiments, such measurements can be performed using relatively inexpensive circuits/components incorporated into the optical front end of the receiver. For a given signaling interval, the DSP runs an iterative algorithm to compute estimates of the in-phase and quadrature components of the optical data signal and achieve a level of performance comparable to that of a coherent optical receiver having a greater number of high-bandwidth photodiodes connected to form balanced photodetectors. The achieved reduction in the number of high-bandwidth photodiodes can advantageously be used, e.g., to significantly reduce the total cost of a high-speed optical transponder.

Claims17

Dependent claims

An apparatus comprising a coherent optical data receiver that comprises:

an optical hybrid configured to mix an optical data signal and an optical local-oscillator signal to generate a plurality of mixed optical signals;
a first photodiode electrically connected in a single-ended configuration and configured to generate a first stream of digitalizations in response to a first one of the mixed optical signals;
a second photodiode electrically connected in a single-ended configuration and configured to generate a second stream of digitalizations in response to a second one of the mixed optical signals;
an averaging circuit configured to generate a third stream of digitalizations providing measurements of average optical power of the optical data signal or measurements of average combined optical power of the optical data and local-oscillator signals, said average corresponding to a plurality of signaling intervals of the optical data signal;
and
a digital signal processor configured to generate estimates of an in-phase component and of a quadrature component of the optical data signal using said first, second, and third streams of digitalizations;
and
wherein the digital signal processor is configured to remove a dc offset corresponding to average optical power of the optical local-oscillator signal from the first and second streams of digitalizations using the third stream of digitalizations.

5 more elements

An apparatus comprising a coherent optical data receiver that comprises:

an optical hybrid configured to mix an optical data signal and an optical local-oscillator signal to generate a plurality of mixed optical signals;
a first photodiode electrically connected in a single-ended configuration and configured to generate a first stream of digitalizations in response to a first one of the mixed optical signals;
a second photodiode electrically connected in a single-ended configuration and configured to generate a second stream of digitalizations in response to a second one of the mixed optical signals;
an averaging circuit configured to generate a third stream of digitalizations providing measurements of average optical power of the optical data signal or measurements of average combined optical power of the optical data and local-oscillator signals, said average corresponding to a plurality of signaling intervals of the optical data signal;
a digital signal processor configured to generate estimates of an in-phase component and of a quadrature component of the optical data signal using said first, second, and third streams of digitalizations and a fourth stream of digitalizations;
and
first and second optical splitters;
wherein the averaging circuit comprises a photodetector configured to generate the third stream of digitalizations in response to a portion of the optical data signal directed thereto by the first optical splitter;
wherein the averaging circuit comprises another photodetector configured to generate the fourth stream of digitalizations in response to a portion of the optical local-oscillator signal directed thereto by the second optical splitter;
wherein the digital signal processor is configured to substantially cancel signal-to-signal beat interference in the first and second streams of digitalizations using the third stream of digitalizations;
and
wherein the digital signal processor is configured to remove a dc offset corresponding to average optical power of the optical local-oscillator signal from the first and second streams of digitalizations using the fourth stream of digitalizations.

9 more elements

Dependencies are inferred from the claim text.