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US 8,275,267 B2Granted
Method, system, and apparatus for filter implementation using hermitian conjugates
AssigneeInfinera Corporation
InventorYuejian Wu
Life of this patent
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Abstract
Filter implementation using Hermitian conjugates and time division multiplexing (TDM) is disclosed to more efficiently compensate for chromatic dispersion of optical signals transmitted over a fiber optic medium. Embodiments for an input, filter, and output sections of a Digital Signal Processor (DSP) are described. The disclosed methods, and corresponding apparatus and systems enables a substantial reduction in the complexity of the hardware needed to implement CD compensation in the DSP. According to another embodiment, Inverse-Fourier transform circuits receive TDM data from the filter section and assemble the TDM data format back to a non-TDM format.
Claims29
An apparatus, comprising:
- a first switch configured to receive first and second groups of bits;
- a second switch configured to receive third and fourth groups of bits;
- a first Fourier transform circuit, the first switch being configured to selectively supply the first group of bits to the first Fourier transform circuit, the first Fourier transform circuit being configured to generate first frequency domain data in response to the first groups of bits;
- a second Fourier transform circuit, the second switch being configured to selectively supply the third group of bits to the second Fourier transform circuit, the second Fourier transform circuit being configured to generate second frequency domain data in response to the third groups of bits;
- a first Hermetian transpose circuit configured to generate a first conjugate of the first frequency domain data, the first conjugate of the first frequency domain data constituting first conjugate data;
- a second Hermetian transpose circuit configured to generate a second conjugate of the second frequency domain data, the second conjugate of the second frequency domain data constituting second conjugate data;
- and
- a filter circuit configured to receive the first and second conjugate data.
5 more elements
A system, comprising:
- a plurality of optical transmitters, each of which being configured to supply a corresponding one of a plurality of optical signals, each of the plurality of optical signals having a corresponding one of a plurality of wavelengths;
- a plurality of receivers, one of which including:
- a plurality of photodiodes, each of which being configured to receive a corresponding portion of one of the plurality of optical signals;
- and
- a plurality of analog-to-digital converter (ADC) circuits, each of which being coupled to a corresponding one of the plurality of photodiodes, each of the plurality of ADC circuits being configured to supply a corresponding one of a plurality of digital signals;
- a first switch configured to receive first and second groups of bits;
- a second switch configured to receive third and fourth groups of bits, at least one of the first, second, third, and fourth group of bits being indicative of at least one of the plurality of digital signals;
- a first Fourier transform circuit, the first switch being configured to selectively supply the first group of bits to the first Fourier transform circuit, the first Fourier transform circuit being configured to generate first frequency domain data in response to the first group of bits;
- a second Fourier transform circuit, the second switch being configured to selectively supply the third group of bits to the second Fourier transform circuit, the second Fourier transform circuit being configured to generate second frequency domain data in response to the third and fourth group of bits;
- a first Hermetian transpose circuit configured to generate a first conjugate of the first frequency domain data, the first conjugate of the first frequency domain data constituting first conjugate data;
- a second Hermetian transpose circuit configured to generate a second conjugate of the second frequency domain data, the second conjugate of the second frequency domain data constituting second conjugate data;
- and
- a filter circuit configured to receive the first and second conjugate data.
10 more elements
A method, comprising:
- receiving first and second groups of bits;
- receiving third and fourth groups of bits;
- selectively supplying the first group of bits to a first Fourier transform circuit during a time interval;
- generating first frequency domain data with the first Fourier transform circuit in response to the first group of bits;
- selectively supplying the third group of bits to a second Fourier transform circuit during the time interval;
- generating second frequency domain data with the second Fourier transform circuit in response to the third group of bits;
- generating a first Hermetian conjugate of the first frequency domain data, the first Hermetian conjugate of the first frequency domain data constituting first conjugate data;
- generating a second Hermetian conjugate of the second frequency domain data, the second Hermetian conjugate of the second frequency domain data constituting second conjugate data;
- multiplying at least a portion of the first conjugate data by a first coefficient;
- and
- multiplying at least a portion of the second conjugate data by a second coefficient.
8 more elements
Dependencies are inferred from the claim text.