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US 9,496,964 B2Granted
Optoelectronic equalizer circuit
AssigneeAlcatel-Lucent USA Inc.
InventorsJeffrey H. Sinsky, Chia-Ming Chang
Life of this patent
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Abstract
We disclose an optoelectronic circuit that is configurable to operate as an FIR filter, in which the tapping and the weighting of the signal that is being equalized are performed in the optical domain, whereas the summation of the weighted signals is performed in the electrical domain after the corresponding optical signals are converted into electrical form using an array of photodetectors. Photodetectors in the array are arranged such that some of them contribute to the equalized electrical signal with a positive polarity and the others contribute to the equalized electrical signal with a negative polarity. As a result, at least some of the tap weights used in the FIR filter can be made variable between a positive value and a negative value.
Claims20
An apparatus comprising:
- an array of photodetectors;
- an optical splitter having an optical input port and a plurality of optical output ports, with each of the optical output ports being connected to illuminate a respective one of the photodetectors in the array of photodetectors;
- a bank of optical delay elements, with each of the optical delay elements being coupled between a respective one of the optical output ports and the respective one of the photodetectors such that light of each of the optical output ports passes through a respective one of the optical delay elements;
- and
- an array of variable optical-gain elements coupled between the optical splitter and the array of photodetectors such that, for at least some of the optical output ports, the light also passes through a respective one of the variable optical-gain elements;
- wherein each photodetector in the array of photodetectors is configured to convert received light into a respective electrical signal;
- wherein the apparatus further comprises an electrical signal combiner configured to combine the respective electrical signals to generate an electrical output signal in a manner that causes a first subset of the photodetectors and a second subset of the photodetectors to contribute the respective electrical signals to the electrical output signal with opposite polarities;
- and
- wherein the apparatus further comprises an electronic controller operatively coupled to the bank of optical delay elements and configured to cause at least one optical delay element in the bank of optical delay elements to change a respective delay time.
6 more elements
An apparatus comprising:
- an array of photodetectors;
- an optical splitter having an optical input port and a plurality of optical output ports, with each of the optical output ports being connected to illuminate a respective one of the photodetectors in the array of photodetectors;
- a bank of optical delay elements, with each of the optical delay elements being coupled between a respective one of the optical output ports and the respective one of the photodetectors such that light of each of the optical output ports passes through a respective one of the optical delay elements;
- and
- an array of variable optical-gain elements coupled between the optical splitter and the array of photodetectors such that, for at least some of the optical output ports, the light also passes through a respective one of the variable optical-gain elements;
- wherein each photodetector in the array of photodetectors is configured to convert received light into a respective electrical signal;
- wherein the apparatus further comprises an electrical signal combiner configured to combine the respective electrical signals to generate an electrical output signal in a manner that causes a first subset of the photodetectors and a second subset of the photodetectors to contribute the respective electrical signals to the electrical output signal with opposite polarities;
- and
- wherein the optical splitter and the array of variable optical-gain elements are implemented as an optical circuit that comprises two or more Mach-Zehnder interferometers.
6 more elements
An apparatus comprising:
- an array of photodetectors;
- an optical splitter having an optical input port and a plurality of optical output ports, with each of the optical output ports being connected to illuminate a respective one of the photodetectors in the array of photodetectors;
- a bank of optical delay elements, with each of the optical delay elements being coupled between a respective one of the optical output ports and the respective one of the photodetectors such that light of each of the optical output ports passes through a respective one of the optical delay elements;
- and
- an array of variable optical-gain elements coupled between the optical splitter and the array of photodetectors such that, for at least some of the optical output ports, the light also passes through a respective one of the variable optical-gain elements;
- wherein each photodetector in the array of photodetectors is configured to convert received light into a respective electrical signal;
- wherein the apparatus further comprises an electrical signal combiner configured to combine the respective electrical signals to generate an electrical output signal in a manner that causes a first subset of the photodetectors and a second subset of the photodetectors to contribute the respective electrical signals to the electrical output signal with opposite polarities;
- wherein each of the optical delay elements is configured to delay the light by a respective delay time, wherein a set of the respective delay times has at least three different values;
- and
- wherein the set of the respective delay times includes the following values:
- τn=τ1+(n−1)τ0,
- where τn is the respective delay time of an n-th delay element in the bank of optical delay elements;
- and τ1 and τ0 are constants.
10 more elements
Dependencies are inferred from the claim text.