Spectral efficiency of coded phase-shift keying for fiber-optic communication

Introduction: This article is based on the recent research work in the field of two subjects: signal data parameters in fiber optic communication links, and dispersive properties of optical signals caused by non-homogeneous material phenomena and multimode propagation of optical signals in such kinds of wired links.Purpose: Studying multimode dispersion by analyzing the propagation of guiding optical waves along a fiber optic cable with various refractive index profiles of the inner optical cable (core) relative to the outer cladding, as well as dispersion properties of a fiber optic cable due to inhomogeneous nature of the cladding along the cable, for two types of signal code sequences transmitted via the cable: return-to-zero and non-return-to-zero ones.Methods: Dispersion properties of multimode propagation inside a fiber optic cable are analyzed with an advanced 3D model of optical wave propagation in a given guiding structure. The effects of multimodal dispersion and material dispersion causing the optical signal delay spread along the cable were investigated analytically and numerically.Results: Time dispersion properties were obtained and graphically illustrated for two kinds of fiber optic structures with different refractive index profiles. The dispersion was caused by multimode (e.g. multi-ray) propagation and by the inhomogeneous nature of the material along the cable. Their effect on the capacity and spectral efficiency of a data signal stream passing through such a guiding optical structure is illustrated for arbitrary refractive indices of the inner (core) and outer (cladding) elements of the optical cable. A new methodology is introduced for finding and evaluating the effects of time dispersion of optical signals propagating in fiber optic structures of various kinds. An algorithm is proposed for estimating the spectral efficiency loss measured in bits per second per Hertz per each kilometer along the cable, for arbitrary presentation of the code signals in the data stream, non-return-to zero or return-to-zero ones. All practical tests are illustrated by MATLAB utility.

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Tributary Mapping Multiplexing an Efficient Technique for High Speed Fiber Optic Communication

Pakistan Journal of Engineering Technology & Science ◽

10.22555/pjets.v6i2.1963 ◽

2018 ◽

Vol 6 (2) ◽

Author(s):

Usman Illahi ◽

Javed Iqbal ◽

Muhammad Ismail Sulaiman ◽

Muhammad Alam ◽

Mazliham Mohd Su'ud

Keyword(s):

Spectral Efficiency ◽

High Speed ◽

Fiber Optic ◽

Single Channel ◽

Efficient Technique ◽

High Dispersion ◽

Optical Filtering ◽

Fiber Optic Communication ◽

Optic Communication ◽

Dispersion Tolerance

<p>A novel technique of multiplexing called Tributary Mapping Multiplexing (TMM) is<br />applied to a single channel wavelength division multiplexing system and performance is monitored on the basis of simulation results. To elaborate the performance of TMM in this paper, a 4-User TMM system over single wavelength channel is demonstrated. TMM showed significant tolerance against narrow optical filtering as compared to that of conventional TDM at the rate of 40 Gbit/s. The above calculations are made by optical filter bandwidth and dispersion tolerance that was allowed at minimum. The spectral efficiency achieved by this TMM was 1 b/s/Hz and it was executed by using transmitters and receivers of 10 Gbit/s without polarized multiplexing. The high spectral efficiency, high dispersion tolerance and tolerance against strong optical filtering makes TMM an efficient technique for High<br />Speed Fiber Optic Communication.</p>

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Experimental evaluation of spectral efficiency from a circular array antenna producing a Laguerre–Gauss mode

Royal Society Open Science ◽

10.1098/rsos.201711 ◽

2020 ◽

Vol 7 (12) ◽

pp. 201711

Author(s):

Ben Allen ◽

Timothy D. Drysdale ◽

Chris Stevens

Keyword(s):

Phase Shift ◽

Antenna Array ◽

Spectral Efficiency ◽

Field Measurements ◽

Modulation Scheme ◽

Phase Shift Keying ◽

Additional Degree ◽

Shift Keying ◽

Mode Purity ◽

Circular Antenna Array

We present the four-dimensional volumetric electromagnetic field measurements ( x , y , z and frequency) of the complex radiated field produced by an 8-element circular antenna array. The array is designed to produce a Laguerre–Gauss (LG) mode l = +1 over the frequency range of 9–10 GHz. We evaluate our findings in terms of far-field LG mode purity and spectral efficiency in terms of the quadrature amplitude modulation (QAM) modulation scheme that can be supported. The application of LG modes in radio systems is as a means of multiplexing several data streams onto the same frequency, polarization and time slot, thus making a highly spectrally efficient transmission system or enhancing radar systems by means of exploiting mode behaviour as an additional degree of freedom. Our results show that for the circular antenna array, we find that mode purity is sufficient to support binary phase shift keying or quadrature phase shift keying modulation over a 0.3 GHz bandwidth, which corresponds to a spectral efficiency of 1.5 b s −1 Hz −1 per mode. Closer to the antennas' design frequency, 256QAM modulation may be supported over a 0.05 GHz band, and which corresponds to a spectral efficiency of 11 b s −1 Hz −1 per mode. We anticipate the practical insights provided in this paper contribute to the successful design of such systems.

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