On ternary phase-shift keyed signaling (Corresp.)

IEEE Trans. Inform. Theory

Szczerba

et al. 2012

We optimize modulation formats for the additive white Gaussian noise channel with nonnegative input, also known as the intensity-modulated direct-detection channel, with and without confining them to a lattice structure. Our optimization criteria are the average electrical, average optical, and peak power. The nonnegative constraint on the input to the channel is translated into a conical constraint in signal space, and modulation formats are designed by sphere packing inside this cone. Some dense packings are found, which yield more power-efficient modulation formats than previously known. For example, at a spectral efficiency of 1.5 bit/s/Hz, the modulation format optimized for average electrical power has a 2.55 dB average electrical power gain over the best known format to achieve a symbol error rate of 10 −6 . The corresponding gains for formats optimized for average and peak optical power are 1.35 and 1.72 dB, respectively. Using modulation formats optimized for peak power in average-power limited systems results in a smaller power penalty than when using formats optimized for average power in peak-power limited systems. We also evaluate the modulation formats in terms of their mutual information to predict their performance in the presence of capacity-achieving errorcorrecting codes, and finally show numerically and analytically that the optimal modulation formats for reliable transmission in the wideband regime have only one nonzero point.

Section: A Optimized Constellationsmentioning

confidence: 99%

Optimizing Constellations for Single-Subcarrier Intensity-Modulated Optical Systems

Karout

IEEE Trans. Inform. Theory

Szczerba

et al. 2012

“…The smallest sensitivity over all sizes M is obtained for M = 3, and the optimal constellation is the triangle, or simplex. It was suggested for modulation in [18,37] under the name ternary phase-shift keying (3-PSK), and it has a γ = (3/4) log 2 3 = 0.75 dB asymptotic sensitivity gain over BPSK. Due to the moderate gain as well as the difficulty of mapping bits to three levels, this format has gained little attention, however.…”

Section: Two-dimensional Constellations N =mentioning

confidence: 99%

Power-Efficient Modulation Schemes

Karlsson

Impact of Nonlinearities on Fiber Optic Communications

2011

Coherent optical fiber communications had a brief period of popularity in the early 1990s, mainly because the optical links of that day were significantly power-limited. Coherent detection provided a possibility of optically amplifying the signal to a power level that, after photodetection, made the thermal noise negligible. Two things, however, caused those coherent systems to be abandoned. The first was the sheer technical difficulties: a coherent receiver requires a local oscillator laser that is to be phase-and polarization-locked to the received signal. This gave rise to significant technical obstacles, and only a few limited and expensive coherent receiver solutions were demonstrated [17,26]. The second was the development of the Erbium-doper fiber amplifier (EDFA) that provided an elegant and practical solution to the problem of the thermal noise. By 1995, the EDFA was a commodity in fiber communication systems, simple on-off keying modulation worked well enough, and coherent communication was forgotten. However, coherent transmission systems got renewed attention around 2005 [12, 34]. This time the motivation was entirely different. A coherent receiver gives access to both the optical phase and amplitude, which provides two important benefits; (i) advanced multilevel modulation formats can be used, that can improve the spectral efficiency; and (ii) electronic distortion mitigation can be used, as the optical field is directly mapped to the electrical signal. Moreover, the practical problems with the coherent detection could now be solved by performing the phase-and polarization tracking by fast digital signal processing. This enabled a third significant

“…The highest γ is seen to arise for M = 3 (3-PSK), at β = 3/2. However, as for all the other 2d clusters (except for QPSK), it has seen limited use, although being discussed in the literature [37,38].…”

Section: Format Optimizations and Comparisonsmentioning

confidence: 99%

Multidimensional Optimized Optical Modulation Formats

Karlsson

Enabling Technologies for High Spectral‐Efficiency Coherent Optical Communication Networks

2016

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