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- Stigwall, Johan, 1977, et al.
(författare)
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Demonstration and analysis of a 40 gigasample/s interferometric analog-to-digital converter
- 2006
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Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 24:3, s. 1247-1256
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Tidskriftsartikel (refereegranskat)abstract
- A novel interferometric scheme for photonic analog-to-digital conversion is for the first time experimentally demonstrated at a real-time sample rate of 40 gigasamples/s. The scheme includes sampling as well as binary encoding, and the input signal in the experiment was a 1.25-GHz sinusoidal tone that was successfully digitized with a nominal resolution of 21 digital levels. Single-sample measurements yielded an effective number of bits (ENOB) of 2.6, which was limited by thermal detection noise while multisample averaged measurements resulted in an ENOB of 3.6 bits, mainly limited by phase drift. Apart from the experimental results, this paper covers an extensive theoretical analysis of the system, including calculations on the fundamental maximum bandwidth, the required optical power, the generated binary code, and its error robustness, as well as the impact of detection noise on the signal-to-noise ratio of the digitized signal. The major benefits of this interferometric scheme are that only one standard phase modulator is required and that the phase swing does not have to be larger than /spl plusmn//spl pi/ to reach the full digital value space.
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| 2. |
- Stigwall, Johan, 1977, et al.
(författare)
-
Signal Reconstruction by Phase Retrieval and Optical Backpropagation in Phase-Diverse Photonic Time-Stretch Systems
- 2007
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Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 25:10, s. 3017-3027
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Tidskriftsartikel (refereegranskat)abstract
- The signal-to-noise ratio and bandwidth of photonictime-stretch (PTS) systems have previously been limited due to thenonlinear distortion caused by modulator response and dispersivepropagation. In this paper, we present a novel method for thereconstruction of the input signal from two phase-diverse intensitymeasurements. The method consists of optical phase retrieval atthe measurement point followed by simulated optical backpropagationto the modulation point. By numerical simulation of a PTSsystem with realistic parameters, we analyze the proposed methodand compare it with the previously suggested maximum ratiocombining (MRC) method. We show that the proposed opticalbackpropagation method, unlike the MRC method that treatsthe system as being linear from electrical input to output, canreconstruct the signal even at a large modulation depth and thatthe method is insensitive to biasing error or drift and not overlysensitive to misestimation of system parameters. Furthermore, toreduce the computational effort associated with the simulationof PTS systems, we present a numerical propagation methodwhereby the required number of sampling points is reduced byseveral orders of magnitude.
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