Multi-Bit Digital-Electrical to Analog-Optical Conversion Based on Non-Linear Optical Element
OwnerIrfan Muhammad Fazalinventor
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Abstract
A digital-electrical to analog-optical converter for converting a N-bit digital data signal uses a periodically poled non-linear waveguide connected to (i) N optical signals each modulated by a corresponding bit stream of the N-bit digital data signal, (ii) N pump optical signals and (iii) a probe optical signal to generate an output optical signal having an amplitude corresponding to the N-bit digital data signal. The output optical signal is filtered out from other optical signals output from the periodically poled non-linear waveguide by an optical filter.
Claims20
A digital to analog converter (DAC) for converting an N-bit digital electrical signal into a corresponding analog optical signal, the DAC comprising:
- N digitally modulated optical bit stream sources, wherein each modulated optical bit stream source is configured for providing an optical signal at a distinct optical frequency fn, wherein the optical signal at the distinct optical frequency fn is modulated according to a respective bit bn of the N-bit digital-electrical signal;
- a non-linear optical element optically coupled to the N digitally modulated optical bit stream sources and configured for outputting a frequency-shifted optical signal when coupled to N complementary optical signals each of the N complementary optical signals having an optical frequency of fn*, wherein fn+fn*=2fqpm for n=1 . . . N, where fqpm is a quasi-phase matching (QPM) frequency of the non-linear optical element, and wherein the frequency-shifted optical signal has an optical frequency of 2fqpm;
- and
- an optical filter optically coupled to an output of the non-linear optical element and configured for outputting the analog optical signal at an optical frequency ffilter while suppressing the optical signals at the optical frequencies fn and fn*, wherein the analog optical signal is based on the frequency-shifted optical signal.
A radio over fiber (RoF) system for transmitting a plurality of analog radio-frequency signals to a plurality of transmission locations, the RoF system comprising:
- a plurality of digital to analog converters (DACs), each of the plurality of DACs for converting an N-bit digital electrical signal into a corresponding analog optical signal and comprising:
- N digitally modulated optical bit stream sources, wherein each modulated optical bit stream source is configured for providing an optical signal at a distinct optical frequency fn, wherein the optical signal at the distinct optical frequency fn is modulated according to a respective bit bn of the N-bit digital-electrical signal;
- a non-linear optical element optically coupled to the N digitally modulated optical bit stream sources and configured for outputting a frequency-shifted optical signal when coupled to N complementary optical signals each of the N complementary optical signals having an optical frequency of fn*, wherein fn+fn*=2fqpm for n=1 . . . N, where fqpm is a quasi-phase matching (QPM) frequency of the non-linear optical element, and wherein the frequency-shifted optical signal has an optical frequency of 2fqpm;
- and
- an optical filter optically coupled to an output of the non-linear optical element and configured for outputting the analog optical signal at an optical frequency ffilter while suppressing the optical signals at the optical frequencies fn and fn*, wherein the analog optical signal is based on the frequency-shifted optical signal;
- a wavelength multiplexer for multiplexing the plurality of analog optical signals output from the optical filters of the plurality of DACs into a single optical fiber output;
- a wavelength demultiplexer for demultiplexing the plurality of optical signals;
- and
- an optical fiber coupling the wavelength multiplexer to the wavelength demultiplexer.
A method of converting an N-bit digital-electrical signal to a corresponding analog-optical signal, the method comprising:
- digitally modulating N optical signals according to N bit streams of the N-bit digital-electrical signal;
- combining the N digitally modulated signals with N pump optical signals in a non-linear optical element;
- and
- filtering an output of the non-linear optical element to provide an output analog optical signal having an amplitude corresponding to the N-bit digital-electrical signal.
Dependencies are inferred from the claim text.