Zhu, X. Ruan, K. Zou, F. Gao, Y. Cai, B. Xu, F. Deynu, K. Google Scholar. Li, M. Erkilinc, K. Shi, E. Sillekens, L. Galdino, T. Xu, B. Thomsen, P. Bayvel, R. Benitez, M. Bolea, J.
Maia, R. Ribeiro, P. Monteiro, "Impact of the modulation depth on self-homodyne optical single sideband systems," in LEOS Chapter Google Scholar. Zhou, J. Yu, Y. Wei, J. Shi, N. Alhasani, Q. Nguyen, G. Ohta, T. Horbatyi, "Research on properties of devices for shaping and processing of signals based on amplitude modulation of many components," Radioelectron.
Kokhanov, "Single sideband quadrature amplitude modulation," Radioelectron. Get Started for Free Download App. Answer Detailed Solution Below Option 4 : 1. Concept: SSB Single Side Band modulation is a technique that allows only one sideband to pass saving bandwidth and power both. Vestigial sideband Single-sideband with carrier Single-sideband suppressed carrier Double-sideband suppressed carrier. Vestigial Sideband: VSB vestigial sideband transmission transmits one sideband fully and the other sideband partially thus, reducing the bandwidth requirement.
Answer Detailed Solution Below Option 4 : The recovered signal has phase offset with fixed amplitude. So the recovered signal has phase offset with fixed amplitude. Concept : SSB Single Side Band modulation is a technique that allows only one sideband to pass saving bandwidth and power both. Exam Preparation Simplified Learn, practice, analyse and improve.
Because the V ratio becomes comes smaller than that of the baseband signal. Because the Vpp ratio becomes unity for pp unity for cut-off frequencies cut-off frequencies greater greater than than 33 GHz, GHz, maximum maximum modulation modulation depth depth can can be be achieved achieved for for Photonics , 8, 67 cut-off frequencies cut-off frequencies greater greater than than 33 GHz. Different Different from from peak peak folding folding and and peak peak clipping, clipping, the 11 ofthe 18 high-pass Hilbert transform allows modulation at higher modulation high-pass Hilbert transform allows modulation at higher modulation depths with lowerdepths with lower spectral degradations spectral degradations duedue to to the the decrease decrease of of V Vpp-H pp-H..
Figure Figure Driving PAPRand PAPR PAPR andoptical and opticalbandwidth optical bandwidthof bandwidth ofthe of themodulator the modulatoroutput modulator outputsignal output signalare signal areplotted are plottedagainst plotted againstthe against the the cut-off cut-off frequency cut-offfrequency frequencyandand presented andpresented in Figure presentedininFigure Figure Peak PAPR reachesunity reaches reaches unityaround unity aroundthe around the the cut-offfrequency cut-off cut-off frequencyof frequency ofGHz.
PAPR Becauseof Because Because ofthe of thefiltering the filteringofof filtering ofHilbert-transformed Hilbert-transformedsignal, Hilbert-transformed signal,residual signal, residual residual bandwidth bandwidth bandwidth of ofof modu- modula- modu- lator tor output output signal signal increases increases with with increasing increasing cut-off cut-off frequency. Spectral Spectral changes changes lator output signal increases with increasing cut-off frequency. Because high-pass Hilbert transform filters out the lower frequencies of the Hilbert-transformed signal spectrum, sideband suppression deteriorates.
Consequently, the dB bandwidth increases almost linearly with the cut-off frequency. The modulator output signal was launched into the fiber link shows in Figure 13 and transmitted. Figure Simulated fiber transmission setup. We assumed ideal phase-diversity homodyne detection at the receiver instead of KK We assumed ideal phase-diversity homodyne detection at the receiver instead of KK relation-based direct detection.
This allows us to clarify the effect of PAPR reduction on relation-based direct detection. This allows us to clarify the effect of PAPR reduction on nonlinear signal distortions during transmission, without bothering to optimize the DSP nonlinear signal distortions during transmission, without bothering to optimize the DSP parameters required for the KK receiver, which is out of the scope of this paper.
For the parameters same reason, required we used fordispersion the KK receiver, which isfiber compensating out of the scope DCF in ourofsimulation this paper.
Chromaticour simulation model to compensate dispersion of fiber dispersion standard instead offiber single-mode frequency-domain equalizationusing SSMF was compensated FDE.
Chromatic We found no waveform degradations during the transmission of DCF. Because using We found the superior no waveform sensitivity degradations characteristics duringdetection of coherent the transmission [23,35,36],ofwe DCF. Here[23,35,36], PIN and Pwe did not employ O represent average any optical amplifiers in our transmission simulations.
We simulated using the split-step Fourier fiber method transmission [37]. At the receiver, the transmitted signal [37]. Fiber param-was eters used in our calculations are given in Table 1. At the receiver, detected using a phase-diversity homodyne detector.
The receiver consisted of a balanced the transmitted signal was detected detector and using a phase-diversity local oscillator LO laser. Here, we assumed ideal phase-matching of simplicity. Figure 14a depicts the back-to-back eye diagram, and the eye diagram of the received signal is presented in Figure 14b. We define the parameter k as the ratio of LO power to received signal power. Figure 15 compares the eye diagrams of the transmitted signal whose PAPR is reduced using the techniques introduced in Sections 3—5.
Back-to-back and transmitted signal eye diagrams, a back-to-back, b after km transmission. Back-to-back and andtransmitted Hilbert-transformed signal signal transmitted eye eyediagrams, component signal a a occurs diagrams, back-to-back, which b b effectively back-to-back, after km increases after the km transmission.
Eye Thediagrams next row of ofthe peak-folded Figure OSSB-SC 15 displays signal are shown the transmitted signal at eyethe top of Figure diagrams 15 of peak- when modulation depth is varied.
Compared eye diagrams with of peak- peak-folding, the eye-opening of the peak-clipped signal slightly increase. Compared The reason for this slight increase of eye-opening is the reduction of high order harmonics with peak-folding, the eye-opening of the peak-clipped signal slightly increase.
The rea- during the modulation, by peak son for this slight clipping. When r is large, eye diagrams of modulation depth 0.
This is because of the nonlinearity of the modulator. For small modulation depths, the modulator operates in its linear region. For larger modulation depths, PAPR becomes less since modulator nonlinearity folds the peaks of Hilbert-transformed signal. For smaller values of r, the clipping amount of the Hilbert-transformed waveform increases. As a result, the baseband signal component becomes dominant.
The effect of modulation depth on the transmitted signal eye degradations disappears giving similar eye openings in both modulation depths. Photonics , 8, 67 For smaller values of r, the clipping amount of the Hilbert-transformed waveform 14 ofin- 18 creases.
The effect of mod- ulation depth on the transmitted signal eye degradations disappears giving similar eye openings in both modulation depths. Despite higher PAPR, high-pass Hilbert transform gives less degraded eyes compared peak-folding and peak-clipping methods. This can be found comparing the eye diagrams of to peak-folding and peak-clipping methods. This can be found comparing the eye dia- Figure One can compare the eye diagrams of peak-folded and peak-clipped signal of modulation depths of 0.
Degradations of high-pass Hilbert-transformed OSSB- signal become less due to the deficiency of high order harmonics in the modulated signal SC signal become less due to the deficiency of high order harmonics in the modulated spectrum. Since there are no waveform degradations of Hilbert-transformed signal during signal spectrum.
Since there are no waveform degradations of Hilbert-transformed signal the PAPR reduction process, broadened mark, space levels are seen in peak-folding and during the PAPR peak-clipping do notreduction appear process, broadened in high-pass mark, space levels Hilbert-transformed are seen inAlong eye diagrams. EO is defined back-to-back eye diagram when modulation depth is 0.
Eye Opening Penalty [dB] 4 Mod. In tively. As As noted noted with with thethe eye eye diagrams, diagrams, the the increase increase in EOP in EOP was was alleviated alleviated at at higher higher modulation modulation depths depths for for peak peak folded folded and and peak peak clipped clipped OSSB-SC signal.
This is because of the peak reduction of the Hilbert-transformed signal component by peak folding and peak clipping at greater modulation depths, respectively. In the high-pass Hilbert transform method, the average fiber input power which EOP starts to increase exponentially becomes higher with increasing cut-off frequency.
InIn the the case case of of peak peak clipping, clipping, peak peak clipping clipping also also starts starts toto occur for modulation depths larger than 0. The SPM threshold of the peak- occur for modulation depths larger than 0. InIn peak peak folding folding and and peak clipping peak clipping methods, methods, thethe SPM SPM threshold threshold can can be be improved improved up up to to 2.
In the used. In 15 ofthe 18 high-pass Hilbert transformed method, an SPM threshold of 9. Depth Depth Mod. Eye-opening Discussion 7. SPM during threshold becomes the transmission. However, In However, PAPRthe case of PAPR reductionpeak clipping, reduction methods methods for peak clipping for optical optical linksalso starts links have have toto to be in be occur for modulation investigated.
The SPM threshold of the investigated. Peak folding using the non- respectively, linearity of comparing of optical to optical modulator the modulator was situation where was originally peak originally studied folding studied to or to suppress clipping suppress the is the noise not noise of used.
PAPR reduction has been substantially studied in wireless transmission. However, PAPR reduction methods for optical links have to be investigated. Peak folding using the nonlinearity of optical modulator was originally studied to suppress the noise of driving signals [38].
In the peak-folding method, peaks of the Hilbert-transformed signal are folded back using the sinusoidal transfer function of the LN modulator. The Peak power was approximately halved while maintaining dB spectral suppression. An SPM threshold improvement of 2. Reduction in spectral suppression is noticed during PAPR reduction. Peak power of the optical SSB-SC signal was reduced to about one-half of the original value with a spectral suppression of 20 dB.
Using peak-clipping, the SPM threshold is improved by 2. Peaks of Hilbert- transformed signal are suppressed by reducing the power of low-frequency components of the spectrum where the energy is concentrated. The all-pass amplitude response of the Hilbert transformer was modified to a high-pass response to reduce the power of lower frequency components of the spectrum. How- ever, the proposed concepts can be extended to other modulation formats and higher transmission rates.
The effectiveness of the proposed methods was confirmed by the analysis of the transmitted signal. SPM threshold of the studied system can be improved by 2.
Besides reducing PAPR, the peak-folding method brings the benefit of driving signal noise suppression. In this study, we focused on a noise-free signal for the sake of simplicity.
SPM threshold can be adjusted according to the demand by choosing the appropriate cut-off frequency in the high-pass Hilbert transform method. It is seen that the reduction of spectral efficiency cannot be avoided during PAPR reduction. Almost similar spectral characteristics were noticed in peak clipping and peak folding methods.
Different from the other two methods, spectral bandwidth increase is noticed in the high-pass Hilbert-transform method during PAPR reduction. Hence, a tech- nique to reduce PAPR should be chosen after taking the available bandwidth into account. Chromatic dispersion of optical fibers has been identified as a limiting factor of next- generation radio over fiber RoF systems [39].
The reach limitation caused by the fiber dispersion is predicted to be severe in radio access networks where capacity improvements are planned to achieve using higher frequencies such as millimeter waves. Different meth- ods such as optical-domain and electrical-domain compensation and O-band transmission have been studied to circumvent this issue of chromatic dispersion [40].
Among those, SSB transmission becomes a strong candidate because of the colorless operation capability and the simple configuration of the receiver.
Author Contributions: Conceptualization, K. All authors have read and agreed to the published version of the manuscript. Conflicts of Interest: The authors declare no conflict of interest. Photonics , 8, 67 17 of 18 References 1. Technology Options for G Implementation. The Ethernet Roadmap. Bakopoulos, P. Hu, Q. Cartledge, J.
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