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Nonlinearity mitigation in bandwidth limited blue LED-based OFDM-UOWC systems using differential pre-emphasis
<!DOCTYPE html> <!--[if IE 8]> <html class="no-js lt-ie9" lang="en" > <![endif]--> <!--[if gt IE 8]><!--> <html class="no-js" lang="en"> <!--<![endif]--> <head> <meta charset="utf-8"> <meta name="tdm-reservation" content="1"/> <meta name="tdm-policy" content="https://opg.optica.org/policies/opg-tdm-policy.json"/> <meta name="viewport" content="width=device-width" initial-scale="1"> <meta http-equiv="X-UA-Compatible" content="IE=Edge"> <meta name="format-detection" content="telephone=no"> <title>Nonlinearity mitigation in bandwidth limited blue LED-based OFDM-UOWC systems using differential pre-emphasis</title> <link title="schema(DC)" rel="schema.dc" href="http://purl.org/dc/elements/1.1/" /> <meta name="twitter:card" content="summary"> <meta name="twitter:description" content="Direct current biased optical orthogonal frequency division multiplexing (DCO-OFDM) is widely used in blue light-emitting diode (LED)–based underwater optical wireless communication (UOWC), but the limited LED bandwidth leads to nonlinear distortions at higher frequencies. Using experiments, this paper proposes and validates a differential pre-emphasis (DPE) scheme for OFDM signal transmission in underwater channels to mitigate LED modulation bandwidth-induced nonlinearity, therefore improving transmission system performance. It is shown that the optimum DPE value leads to shorter rise time and fall time of the received signal and also avoids over- and under-shoots. The DPE scheme is validated through numerical simulations for QPSK, 16-QAM, and 64-QAM at symbol rates of 10&#x00A0;MS/s, 20&#x00A0;MS/s, and 25&#x00A0;MS/s, respectively, with an LED bandwidth of 8&#x00A0;MHz. The bit error rate (BER) performances are estimated at different values of the DPE factor for each modulation format and symbol rate. The simulation results indicate an optimized modulation format and symbol rate-dependent DPE factor for achieving minimum BER values. We further validate the DPE scheme on QPSK, 16-QAM, and 64-QAM-based OFDM transmissions in a 2.5&#x00A0;m tap water UOWC experimental setup. Results confirm that the optimized DPE factor depends on the modulation format and symbol rate for achieving the best BER performance. Experimental results show that the DPE scheme improves BER performance significantly, providing over 4 orders of BER improvement for all modulation formats at their respective maximum symbol rates. Successful transmissions of the OFDM signal at data rates of 24.09&#x00A0;Mb/s for QPSK, 48.19&#x00A0;Mb/s for 16-QAM, and 72.28&#x00A0;Mb/s for 64-QAM using an 8&#x00A0;MHz blue-LED-based transmitter in the presence and absence of air-bubble-induced turbulence in the water channel are experimentally demonstrated in this paper."> <meta name="twitter:image" content="https://opg.optica.org/getThumbnail.cfm?uri=ao-63-34-8857&o=y"> <meta name="twitter:site" content="@OpticaPubsGroup"> <meta name="twitter:title" content="Nonlinearity mitigation in bandwidth limited blue LED-based OFDM-UOWC systems using differential pre-emphasis"> <meta name="dc.creator" content="Jimson Mathew"> <meta name="dc.creator" content="Sumanta Gupta"> <meta name="dc.creator" content="Gopal Krishna"> <meta name="dc.date" content="2024-12-01"> <meta name="dc.description" content="Direct current biased optical orthogonal frequency division multiplexing (DCO-OFDM) is widely used in blue light-emitting diode (LED)–based underwater optical wireless communication (UOWC), but the limited LED bandwidth leads to nonlinear distortions at higher frequencies. Using experiments, this paper proposes and validates a differential pre-emphasis (DPE) scheme for OFDM signal transmission in underwater channels to mitigate LED modulation bandwidth-induced nonlinearity, therefore improving transmission system performance. It is shown that the optimum DPE value leads to shorter rise time and fall time of the received signal and also avoids over- and under-shoots. The DPE scheme is validated through numerical simulations for QPSK, 16-QAM, and 64-QAM at symbol rates of 10&#x00A0;MS/s, 20&#x00A0;MS/s, and 25&#x00A0;MS/s, respectively, with an LED bandwidth of 8&#x00A0;MHz. The bit error rate (BER) performances are estimated at different values of the DPE factor for each modulation format and symbol rate. The simulation results indicate an optimized modulation format and symbol rate-dependent DPE factor for achieving minimum BER values. We further validate the DPE scheme on QPSK, 16-QAM, and 64-QAM-based OFDM transmissions in a 2.5&#x00A0;m tap water UOWC experimental setup. Results confirm that the optimized DPE factor depends on the modulation format and symbol rate for achieving the best BER performance. Experimental results show that the DPE scheme improves BER performance significantly, providing over 4 orders of BER improvement for all modulation formats at their respective maximum symbol rates. Successful transmissions of the OFDM signal at data rates of 24.09&#x00A0;Mb/s for QPSK, 48.19&#x00A0;Mb/s for 16-QAM, and 72.28&#x00A0;Mb/s for 64-QAM using an 8&#x00A0;MHz blue-LED-based transmitter in the presence and absence of air-bubble-induced turbulence in the water channel are experimentally demonstrated in this paper."> <meta name="dc.identifier" content="doi:10.1364/AO.540838"> <meta name="dc.language" content="EN"> <meta property="og:description" content="Direct current biased optical orthogonal frequency division multiplexing (DCO-OFDM) is widely used in blue light-emitting diode (LED)–based underwater optical wireless communication (UOWC), but the limited LED bandwidth leads to nonlinear distortions at higher frequencies. Using experiments, this paper proposes and validates a differential pre-emphasis (DPE) scheme for OFDM signal transmission in underwater channels to mitigate LED modulation bandwidth-induced nonlinearity, therefore improving transmission system performance. It is shown that the optimum DPE value leads to shorter rise time and fall time of the received signal and also avoids over- and under-shoots. The DPE scheme is validated through numerical simulations for QPSK, 16-QAM, and 64-QAM at symbol rates of 10&#x00A0;MS/s, 20&#x00A0;MS/s, and 25&#x00A0;MS/s, respectively, with an LED bandwidth of 8&#x00A0;MHz. The bit error rate (BER) performances are estimated at different values of the DPE factor for each modulation format and symbol rate. The simulation results indicate an optimized modulation format and symbol rate-dependent DPE factor for achieving minimum BER values. We further validate the DPE scheme on QPSK, 16-QAM, and 64-QAM-based OFDM transmissions in a 2.5&#x00A0;m tap water UOWC experimental setup. Results confirm that the optimized DPE factor depends on the modulation format and symbol rate for achieving the best BER performance. Experimental results show that the DPE scheme improves BER performance significantly, providing over 4 orders of BER improvement for all modulation formats at their respective maximum symbol rates. Successful transmissions of the OFDM signal at data rates of 24.09&#x00A0;Mb/s for QPSK, 48.19&#x00A0;Mb/s for 16-QAM, and 72.28&#x00A0;Mb/s for 64-QAM using an 8&#x00A0;MHz blue-LED-based transmitter in the presence and absence of air-bubble-induced turbulence in the water channel are experimentally demonstrated in this paper."> <meta property="og:image" content="https://opg.optica.org/getThumbnail.cfm?uri=ao-63-34-8857&size=200&o=y"> <meta property="og:sitename" content="Optica Publishing Group"> <meta property="og:title" content="Nonlinearity mitigation in bandwidth limited blue LED-based OFDM-UOWC systems using differential pre-emphasis"> <meta property="og:type" content="Article"> <meta property="og:url" content="https://opg.optica.org/ao/abstract.cfm?uri=ao-63-34-8857"> <meta name="dc.publisher" content="Optica Publishing Group"> <meta name="dc.rights" content="&#169; 2024 Optica Publishing Group"> <meta name="dc.source" content="Applied Optics, Vol. 63, Issue 34, pp. 8857-8868"> <meta name="dc.subject" content="Blue light emitting diodes"> <meta name="dc.subject" content="Frequency division multiplexing"> <meta name="dc.subject" content="Optical wireless communication"> <meta name="dc.subject" content="Signal transmission"> <meta name="dc.subject" content="Visible light communications"> <meta name="dc.subject" content="White light emitting diodes"> <meta name="dc.title" content="Nonlinearity mitigation in bandwidth limited blue LED-based OFDM-UOWC systems using differential pre-emphasis"> <meta name="citation_abstract_html_url" content="https://opg.optica.org/abstract.cfm?uri=ao-63-34-8857"> <meta name="citation_author" content="Gopal Krishna"> <meta name="citation_author_institution" content="Department of Electrical Engineering, Indian Institute of Technology Patnahttps://ror.org/01ft5vz71, Bihta 801103, India"> <meta name="citation_author" content="Jimson Mathew"> <meta name="citation_author_institution" content="Department of Computer Science Engineering, Indian Institute of Technology Patna, Bihta 801103, India"> <meta name="citation_author" content="Sumanta Gupta"> <meta name="citation_author_institution" content="Department of Electrical Engineering, Indian Institute of Technology Patnahttps://ror.org/01ft5vz71, Bihta 801103, India"> <meta name="citation_doi" content="10.1364/AO.540838"> <meta name="citation_firstpage" content="8857"> <meta name="citation_fulltext_html_url" content="https://opg.optica.org/viewmedia.cfm?uri=ao-63-34-8857&seq=0&html=true"> <meta name="citation_issn" content="2155-3165"> <meta name="citation_issue" content="34"> <meta name="citation_journal_abbrev" content="Appl. Opt., AO"> <meta name="citation_journal_title" content="Applied Optics"> <meta name="citation_keywords" content="Blue light emitting diodes;Frequency division multiplexing;Optical wireless communication;Signal transmission;Visible light communications;White light emitting diodes;"> <meta name="citation_language" content="EN"> <meta name="citation_lastpage" content="8868"> <meta name="citation_online_date" content="2024/11/22"> <meta name="citation_pdf_url" content="https://opg.optica.org/viewmedia.cfm?uri=ao-63-34-8857&seq=0"> <meta name="citation_publication_date" content="2024/12/01"> <meta name="citation_publisher" content="Optica Publishing Group"> <meta name="citation_title" content="Nonlinearity mitigation in bandwidth limited blue LED-based OFDM-UOWC systems using differential pre-emphasis"> <meta name="citation_volume" content="63"> <meta name="citation_reference" content=""> <meta name="citation_reference" content=""> <meta name="citation_reference" content=""> <meta name="citation_reference" content=""> <meta name="citation_reference" content=""> <meta name="citation_reference" content=""> <meta name="citation_reference" content=""> <meta name="citation_reference" content=""> <meta name="citation_reference" content=""> <meta name="citation_reference" content=""> <meta name="citation_reference" content=""> <meta name="citation_reference" content=""> <meta name="citation_reference" content=""> <meta name="citation_reference" content=""> <meta name="citation_reference" content=""> <meta name="citation_reference" content=""> <meta name="citation_reference" content=""> <meta name="citation_reference" content=""> <meta name="citation_reference" content=""> <meta name="citation_reference" content=""> <meta name="citation_reference" content=""> <meta name="citation_reference" content=""> <meta name="citation_reference" content=""> <meta name="citation_reference" content=""> <meta name="citation_reference" content=""> <meta name="citation_reference" content=""> <meta name="citation_reference" content=""> <meta name="citation_reference" content=""> <meta name="citation_reference" content=""> <meta name="citation_reference" content=""> <meta name="citation_reference" content=""> <meta name="citation_reference" content=""> <!-- Google Tag Manager --> <script>(function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start': new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0], j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src= 'https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f); 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mb-1" style=""> <h1 class="article-title"> Nonlinearity mitigation in bandwidth limited blue LED-based OFDM-UOWC systems using differential pre-emphasis </h1> <p class="article-authors"> Gopal Krishna, Jimson Mathew, and Sumanta Gupta </p> <div> <div class="btn-group article-affiliations-dropdown dropdown hidden-xs mr-2"> <a data-bs-toggle="dropdown" id="author-affiliations-dropdown"> Author Information <span class="caret"></span> </a> <div id="authorAffiliations" class="article-author-affiliations dropdown-menu"> <h5>Author Affiliations</h5> <p><strong> Gopal Krishna,<sup>1</sup> Jimson Mathew,<sup>2</sup> and Sumanta Gupta<sup>1,</sup><sup>*</sup> </strong></p> <p><em> <sup>1</sup>Department of Electrical Engineering, Indian Institute of Technology Patna, Bihta 801103, India </em></p> <p><em> <sup>2</sup>Department of Computer Science Engineering, Indian Institute of Technology Patna, Bihta 801103, India </em></p> <p> <sup>*</sup>Corresponding author: <a href="mailto:sumanta@iitp.ac.in">sumanta@iitp.ac.in</a> </p> <h5 class="mb-0">ORCID</h5> <table> <tr> <td><strong>Gopal <?xml version="1.0" encoding="UTF-8"?><surname>Krishna</surname></strong></td> <td nowrap class="pl-1"><a href="https://orcid.org/0000-0002-7750-363X" target="_blank" class="orcida"><img class="orcid-logo" src="/images/orcid_16x16.png" alt="orcid link"></a> <a href="https://orcid.org/0000-0002-7750-363X" target="_blank" class="orcida">https://orcid.org/0000-0002-7750-363X</a></td> </tr> </table> </div> </div> <div class="btn-group hidden-xs hidden-sm"> <a data-bs-toggle="dropdown" id="search-by-author-dropdown"> <i class="fal fa-search p__1--sm"></i> Find other works by these authors <span class="caret"></span> </a> <ul class="dropdown-menu" id="search-by-author"> <li><a href="search.cfm?a=G Krishna">G Krishna</a></li> <li><a href="search.cfm?a=J Mathew">J Mathew</a></li> <li><a href="search.cfm?a=S Gupta">S Gupta</a></li> </ul> </div> </div> </div> </div> </div> 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Using experiments, this paper proposes and validates a differential pre-emphasis (DPE) scheme for OFDM signal transmission in underwater channels to mitigate LED modulation bandwidth-induced nonlinearity, therefore improving transmission system performance. It is shown that the optimum DPE value leads to shorter rise time and fall time of the received signal and also avoids over- and under-shoots. The DPE scheme is validated through numerical simulations for QPSK, 16-QAM, and 64-QAM at symbol rates of 10 MS/s, 20 MS/s, and 25 MS/s, respectively, with an LED bandwidth of 8 MHz. The bit error rate (BER) performances are estimated at different values of the DPE factor for each modulation format and symbol rate. The simulation results indicate an optimized modulation format and symbol rate-dependent DPE factor for achieving minimum BER values. We further validate the DPE scheme on QPSK, 16-QAM, and 64-QAM-based OFDM transmissions in a 2.5 m tap water UOWC experimental setup. Results confirm that the optimized DPE factor depends on the modulation format and symbol rate for achieving the best BER performance. Experimental results show that the DPE scheme improves BER performance significantly, providing over 4 orders of BER improvement for all modulation formats at their respective maximum symbol rates. Successful transmissions of the OFDM signal at data rates of 24.09 Mb/s for QPSK, 48.19 Mb/s for 16-QAM, and 72.28 Mb/s for 64-QAM using an 8 MHz blue-LED-based transmitter in the presence and absence of air-bubble-induced turbulence in the water channel are experimentally demonstrated in this paper.</p></p> <p>© 2024 Optica Publishing Group. All rights, including for text and data mining (TDM), Artificial Intelligence (AI) training, and similar technologies, are reserved.</p> <a href="viewmedia.cfm?uri=ao-63-34-8857&seq=0&html=true" id="link-full">Full Article</a> | <a href="viewmedia.cfm?uri=ao-63-34-8857&seq=0" target="_blank" id="link-pdf">PDF Article</a> <hr style="margin-top:5em;"> <strong>More Like This</strong> <div class="content-item media-twbs"> <div class="media-twbs-left"> <img class="media-object" src="/getThumbnail.cfm?uri=oe-30-15-28014&o=y" width="50" height="50" aria-hidden="true" role="presentation"> </div> <div class="media-twbs-body"> <a class="js-relatedArticleLink" href="/oe/abstract.cfm?uri=oe-30-15-28014">4-bit DAC based 6.9Gb/s PAM-8 UOWC system using single-pixel mini-LED and digital pre-compensation</a> <p>Chen Cheng, Xueyang Li, Qian Xiang, Jun Li, Yongchao Jin, Zixian Wei, H. Y. Fu, and Yanfu Yang<br> <span class="muted">Opt. 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aria-hidden="true">×</button> <h4 class="modal-title" id="tablet001Label">Table 1.</h4> </div> <div class="modal-body"> <h4>Simulation Parameters</h4> <div class="table-responsive"><?xml version="1.0" encoding="UTF-8"?><table CLASS="table" frame="hsides" rules="groups" width="240"><colgroup span="1"><col align="left" span="1" width="0%"/><col align="center" span="1" width="0%"/></colgroup><thead><tr><th colspan="1" rowspan="1">Parameter</th><th colspan="1" rowspan="1">Value</th></tr></thead><tbody><tr><td colspan="1" rowspan="1">Separation</td><td colspan="1" rowspan="1">2.5 m</td></tr><tr><td colspan="1" rowspan="1">Half viewing angle</td><td colspan="1" rowspan="1">8°</td></tr><tr><td colspan="1" rowspan="1">Gain of optical filter</td><td colspan="1" rowspan="1">0.9</td></tr><tr><td colspan="1" rowspan="1">Half angle view of optical lens</td><td colspan="1" rowspan="1">70°</td></tr><tr><td colspan="1" rowspan="1">Responsivity</td><td colspan="1" rowspan="1">12.6 A/W</td></tr><tr><td colspan="1" rowspan="1">Active area of PD</td><td colspan="1" rowspan="1">3 mm</td></tr><tr><td colspan="1" rowspan="1">Modulation bandwidth of LED</td><td colspan="1" rowspan="1">8 MHz</td></tr><tr><td colspan="1" rowspan="1">Gain</td><td colspan="1" rowspan="1">30</td></tr><tr><td colspan="1" rowspan="1">Center wavelength (<inline-formula><alternatives><math display="inline"> <mi>λ</mi> </math></alternatives></inline-formula>)</td><td colspan="1" rowspan="1">465 nm</td></tr><tr><td colspan="1" rowspan="1">Transmitted power</td><td colspan="1" rowspan="1">10 mW</td></tr><tr><td colspan="1" rowspan="1">Emission (<inline-formula><alternatives><math display="inline"> <mi>ϕ</mi> </math></alternatives></inline-formula>) and receiving angle (<inline-formula><alternatives><math display="inline"> <mi>ψ</mi> </math></alternatives></inline-formula>)</td><td colspan="1" rowspan="1">0°</td></tr><tr><td colspan="1" rowspan="1">Absorption coefficient</td><td colspan="1" rowspan="1"><inline-formula><alternatives><math display="inline"> <mrow class="MJX-TeXAtom-ORD"> <mn>0.040</mn> </mrow> <mspace width="thickmathspace"/> <mrow class="MJX-TeXAtom-ORD"> <msup> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">m</mi> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mo>−</mo> <mn>1</mn> </mrow> </msup> </mrow> </math></alternatives></inline-formula></td></tr><tr><td colspan="1" rowspan="1">Scattering coefficient</td><td colspan="1" rowspan="1"><inline-formula><alternatives><math display="inline"> <mrow class="MJX-TeXAtom-ORD"> <mn>0.002</mn> </mrow> <mspace width="thickmathspace"/> <mrow class="MJX-TeXAtom-ORD"> <msup> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">m</mi> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mo>−</mo> <mn>1</mn> </mrow> </msup> </mrow> </math></alternatives></inline-formula></td></tr><tr><td colspan="1" rowspan="1">Attenuation coefficient (<inline-formula><alternatives><math display="inline"> <mi>k</mi> </math></alternatives></inline-formula>)</td><td colspan="1" rowspan="1"><inline-formula><alternatives><math display="inline"> <mrow class="MJX-TeXAtom-ORD"> <mn>0.043</mn> </mrow> <mspace width="thickmathspace"/> <mrow class="MJX-TeXAtom-ORD"> <msup> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">m</mi> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mo>−</mo> <mn>1</mn> </mrow> </msup> </mrow> </math></alternatives></inline-formula></td></tr></tbody></table></div> </div> <div class="modal-footer"> <button type="button" class="btn btn-default" data-bs-dismiss="modal">Close</button> </div> </div> </div> </div> <div class="modal fade full" id="tablet002" tabindex="-1" role="dialog" aria-labelledby="tablet002Label" aria-hidden="true"> <div class="modal-dialog"> <div class="modal-content"> <div class="modal-header"> <button type="button" class="close" data-bs-dismiss="modal" aria-hidden="true">×</button> <h4 class="modal-title" id="tablet002Label">Table 2.</h4> </div> <div class="modal-body"> <h4>Experimental Parameters</h4> <div class="table-responsive"><?xml version="1.0" encoding="UTF-8"?><table CLASS="table" frame="hsides" rules="groups" width="240"><colgroup span="1"><col align="left" span="1" width="50%"/><col align="center" span="1" width="50%"/></colgroup><thead><tr><th colspan="1" rowspan="1">Parameter</th><th colspan="1" rowspan="1">Value</th></tr></thead><tbody><tr><td colspan="1" rowspan="1">FFT/IFFT points</td><td colspan="1" rowspan="1">1024</td></tr><tr><td colspan="1" rowspan="1">CP length</td><td colspan="1" rowspan="1">8</td></tr><tr><td colspan="1" rowspan="1">Data subcarriers</td><td colspan="1" rowspan="1">500</td></tr><tr><td colspan="1" rowspan="1">LED bias</td><td colspan="1" rowspan="1">3.2 V, 10 mA</td></tr><tr><td colspan="1" rowspan="1">Peak to peck signal</td><td colspan="1" rowspan="1">1 V</td></tr><tr><td colspan="1" rowspan="1">APD voltage</td><td colspan="1" rowspan="1">5 V, 42 mA</td></tr><tr><td colspan="1" rowspan="1">Modulation format</td><td colspan="1" rowspan="1">QPSK/16-QAM/64-QAM</td></tr><tr><td colspan="1" rowspan="1">AWG sampling rate</td><td colspan="1" rowspan="1">10/20/25 MSa/s</td></tr><tr><td colspan="1" rowspan="1">DSO sampling rate</td><td colspan="1" rowspan="1">100/200/250 MSa/s</td></tr></tbody></table></div> </div> <div class="modal-footer"> <button type="button" class="btn btn-default" data-bs-dismiss="modal">Close</button> </div> </div> </div> </div> <div class="modal fade full" id="allTablesModal" tabindex="-1" role="dialog" aria-labelledby="allTablesLabel" aria-hidden="true"> <div class="modal-dialog"> <div class="modal-content"> <div class="modal-header"> <button type="button" class="close" data-bs-dismiss="modal" aria-hidden="true">×</button> <h4 class="modal-title" id="allTablesLabel">Tables (2)</h4> </div> <div class="modal-body"> <h4>Table 1.</h4> <p>Simulation Parameters</p> <div class="table-responsive"><?xml version="1.0" encoding="UTF-8"?><table CLASS="table" frame="hsides" rules="groups" width="240"><colgroup span="1"><col align="left" span="1" width="0%"/><col align="center" span="1" width="0%"/></colgroup><thead><tr><th colspan="1" rowspan="1">Parameter</th><th colspan="1" rowspan="1">Value</th></tr></thead><tbody><tr><td colspan="1" rowspan="1">Separation</td><td colspan="1" rowspan="1">2.5 m</td></tr><tr><td colspan="1" rowspan="1">Half viewing angle</td><td colspan="1" rowspan="1">8°</td></tr><tr><td colspan="1" rowspan="1">Gain of optical filter</td><td colspan="1" rowspan="1">0.9</td></tr><tr><td colspan="1" rowspan="1">Half angle view of optical lens</td><td colspan="1" rowspan="1">70°</td></tr><tr><td colspan="1" rowspan="1">Responsivity</td><td colspan="1" rowspan="1">12.6 A/W</td></tr><tr><td colspan="1" rowspan="1">Active area of PD</td><td colspan="1" rowspan="1">3 mm</td></tr><tr><td colspan="1" rowspan="1">Modulation bandwidth of LED</td><td colspan="1" rowspan="1">8 MHz</td></tr><tr><td colspan="1" rowspan="1">Gain</td><td colspan="1" rowspan="1">30</td></tr><tr><td colspan="1" rowspan="1">Center wavelength (<inline-formula><alternatives><math display="inline"> <mi>λ</mi> </math></alternatives></inline-formula>)</td><td colspan="1" rowspan="1">465 nm</td></tr><tr><td colspan="1" rowspan="1">Transmitted power</td><td colspan="1" rowspan="1">10 mW</td></tr><tr><td colspan="1" rowspan="1">Emission (<inline-formula><alternatives><math display="inline"> <mi>ϕ</mi> </math></alternatives></inline-formula>) and receiving angle (<inline-formula><alternatives><math display="inline"> <mi>ψ</mi> </math></alternatives></inline-formula>)</td><td colspan="1" rowspan="1">0°</td></tr><tr><td colspan="1" rowspan="1">Absorption coefficient</td><td colspan="1" rowspan="1"><inline-formula><alternatives><math display="inline"> <mrow class="MJX-TeXAtom-ORD"> <mn>0.040</mn> </mrow> <mspace width="thickmathspace"/> <mrow class="MJX-TeXAtom-ORD"> <msup> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">m</mi> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mo>−</mo> <mn>1</mn> </mrow> </msup> </mrow> </math></alternatives></inline-formula></td></tr><tr><td colspan="1" rowspan="1">Scattering coefficient</td><td colspan="1" rowspan="1"><inline-formula><alternatives><math display="inline"> <mrow class="MJX-TeXAtom-ORD"> <mn>0.002</mn> </mrow> <mspace width="thickmathspace"/> <mrow class="MJX-TeXAtom-ORD"> <msup> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">m</mi> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mo>−</mo> <mn>1</mn> </mrow> </msup> </mrow> </math></alternatives></inline-formula></td></tr><tr><td colspan="1" rowspan="1">Attenuation coefficient (<inline-formula><alternatives><math display="inline"> <mi>k</mi> </math></alternatives></inline-formula>)</td><td colspan="1" rowspan="1"><inline-formula><alternatives><math display="inline"> <mrow class="MJX-TeXAtom-ORD"> <mn>0.043</mn> </mrow> <mspace width="thickmathspace"/> <mrow class="MJX-TeXAtom-ORD"> <msup> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">m</mi> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mo>−</mo> <mn>1</mn> </mrow> </msup> </mrow> </math></alternatives></inline-formula></td></tr></tbody></table></div> <h4>Table 2.</h4> <p>Experimental Parameters</p> <div class="table-responsive"><?xml version="1.0" encoding="UTF-8"?><table CLASS="table" frame="hsides" rules="groups" width="240"><colgroup span="1"><col align="left" span="1" width="50%"/><col align="center" span="1" width="50%"/></colgroup><thead><tr><th colspan="1" rowspan="1">Parameter</th><th colspan="1" rowspan="1">Value</th></tr></thead><tbody><tr><td colspan="1" rowspan="1">FFT/IFFT points</td><td colspan="1" rowspan="1">1024</td></tr><tr><td colspan="1" rowspan="1">CP length</td><td colspan="1" rowspan="1">8</td></tr><tr><td colspan="1" rowspan="1">Data subcarriers</td><td colspan="1" rowspan="1">500</td></tr><tr><td colspan="1" rowspan="1">LED bias</td><td colspan="1" rowspan="1">3.2 V, 10 mA</td></tr><tr><td colspan="1" rowspan="1">Peak to peck signal</td><td colspan="1" rowspan="1">1 V</td></tr><tr><td colspan="1" rowspan="1">APD voltage</td><td colspan="1" rowspan="1">5 V, 42 mA</td></tr><tr><td colspan="1" rowspan="1">Modulation format</td><td colspan="1" rowspan="1">QPSK/16-QAM/64-QAM</td></tr><tr><td colspan="1" rowspan="1">AWG sampling rate</td><td colspan="1" rowspan="1">10/20/25 MSa/s</td></tr><tr><td colspan="1" rowspan="1">DSO sampling rate</td><td colspan="1" rowspan="1">100/200/250 MSa/s</td></tr></tbody></table></div> </div> <div class="modal-footer"> <button type="button" class="btn btn-default" data-bs-dismiss="modal">Close</button> </div> </div> </div> </div> <script type="text/Javascript"> function alertconfirmed() { // Send ajax to confirm document.getElementById('confirmAlertButton').disabled = 'disabled'; $.ajax({ cache: false, type: "GET", url: "set_citation_alert.cfm?uri=ao-63-34-8857&confirmalert=true" }).done(function( ajxretmsg ) { if (ajxretmsg == "1") { 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for="facet-publications-proceedings">Conferences <span class="facet-count">(<%= totalProceedings %>)</span></label></li> <li class="sf-list_list-item"><input id="facet-publications-reports" class="sf-list_input" type="checkbox" name="reports"/> <label class="sf-list_label" for="facet-publications-reports">Industry Reports <span class="facet-count">(<%= totalReports %>)</span></label></li> </ul> </div> <div class="sf-module sf-journals"> <div class="row2"> <p id="facet-journal-show" class="sf-group-title collapsed" style="text-transform: none !important;">Journals</p> <div id="sortJournal" class="sf-sort"></div> </div> <div id="facet-journal-values"> </div> </div> <div class="sf-module sf-proceedings"> <div class="row2"> <p id="facet-proceeding-show" class="sf-group-title collapsed" style="text-transform: none !important;">Conferences</p> <div id="sortProceeding" class="sf-sort"></div> </div> <div id="facet-proceeding-values"></div> </div> </script> <script type="text/template" id="search-result-facet-basics"> <ul class="sf-list"> <li class="sf-select-all"><input id="<%= allId %>" type="checkbox" checked="checked" disabled="disabled"/> <label for="<%= allId %>">All</label></li> <%= values %> <li class="sf-expanded"> <a href="#" id="more-<%= allId %>" class="search-panel_more-link" data-bs-toggle="modal" data-bs-target="#modal-<%= allId %>">more <%=name%> »</a> <div class="modal full fade" id="modal-<%= allId %>"> <div class="modal-dialog"> <div class="modal-content search"> <div class="row mbottom-20"> <div class="col-md-4"> <h3 class="modal-header search"><%= modalTitle %></h3> </div> <div class="col-md-6 col-md-offset-2"> <input id="input-<%= allId%>" type="text" class="form-control selectized" placeholder="(type names or look up list)" tabindex="-1" aria-label="type names or look up list"></input> <div class="selectize-control form-control multi"></div> </div> </div> <div class="modal_option-container mbottom-20 scrollable" id="moreUl-<%=allId%>"> </div> <hr> <div class="d-flex"> <a href="#" id="apply-<%= allId %>" class="btn btn-primary mr-1" data-bs-dismiss="modal">Apply Filters</a> <a href="#" id="cancel-<%= allId %>" class="btn btn-default" data-bs-dismiss="modal">Cancel</a> </div> </div> </div> </div> </li> </ul> </script> <script type="text/template" id="search-result-facet-terms"> <ul class="sf-list"> <li class="sf-select-all"> <input id="<%= allId %>" type="checkbox" checked="checked" disabled="disabled"/> <label for="<%= allId %>">Remove all topic filters</label> </li> <%= values %> <li class="sf-expanded"> <a href="#" id="more-<%= allId %>" class="search-panel_more-link hidden-xs" data-bs-toggle="modal" data-bs-target="#modal-<%= allId %>">include more topics »</a> <div class="modal full fade" id="modal-<%= allId %>"> <div class="modal-dialog"> <div class="modal-content search"> <div class="row mbottom-20"> <div class="col-md-4"> <h3 class="modal-header search">Optics & Photonics Topics</h3> </div> <div class="col-md-6 col-md-offset-2"> <input id="input-<%= allId%>" type="text" class="form-control" placeholder="Search for a specific topic" tabindex="-1" aria-label="Search for a specific topic"></input> </div> </div> <div class="row mbottom-20"> <div class="col-md-12"> <strong>Browse the topics:</strong> Click the <svg class="selection-list_arrow"><use xlink:href="#right-arrow" /></svg> to reveal subtopics. Use the checkbox to select a topic to filter your search. </div> </div> <div class="modal_option-container mbottom-20 scrollable" id="moreUl-<%=allId%>"> </div> <div class="row"> <div class="col-md-12"> <strong>Selected Topics</strong> </div> </div> <div id="moreSelectedList"></div> <div class="row"><div class="col-md-12"> <!-- spacing row --></div></div> <div class="d-flex"> <a href="#" id="apply-<%= allId %>" class="btn btn-primary mr-1" data-bs-dismiss="modal">Add Selected Topic Filters</a> <a href="#" id="cancel-<%= allId %>" class="btn btn-default" data-bs-dismiss="modal">Cancel</a> </div> </div> </div> </div> </li> </ul> </script> <script type="text/template" id="search-result-facet-journal-proceedings"> <ul class="sf-list"> <li class="sf-select-all"><input id="<%= allId %>" type="checkbox" checked> <label for="<%= allId %>">All</label></li> <%= values %> <li class="sf-expanded"> <a href="#" id="more-<%= allId %>" class="search-panel_more-link" data-bs-toggle="modal" data-bs-target="#modal-<%= allId %>" class="sf-expanded-toggle">more <%=name%> »</a> <div class="modal full fade" id="modal-<%= allId %>"> <div class="modal-dialog"> <div class="modal-content search"> <div class="row mbottom-20"> <div class="col-md-4"> <h3 class="modal-header search"><%= modalTitle%></h3> </div> <div class="col-md-6 col-md-offset-2"> <input id="input-<%= allId%>" type="text" class="form-control selectized" placeholder="(type names or look up list)" tabindex="-1" aria-label="type names or look up list"></input> <div class="selectize-control form-control multi"></div> </div> </div> <div class="modal_option-container mbottom-20 scrollable" id="moreUl-<%=allId%>"> </div> <hr> <div class="d-flex"> <a href="#" id="apply-<%= allId %>" class="btn btn-primary mr-1" data-bs-dismiss="modal">Apply Filters</a> <a href="#" id="cancel-<%= allId %>" class="btn btn-default" data-bs-dismiss="modal">Cancel</a> </div> </div> </div> </div> </li> </ul> </script> <script type="text/template" id="search-result-facet-content"> <ul class="sf-list"> <%= values %> </ul> </script> <script type="text/template" id="facet-more-new-content"> <div class="more-columns_container"> <div class="more-columns_column"><ul class="selection-list"><%= val1%></ul></div> <div class="more-columns_column"><ul class="selection-list"><%= val2%></ul></div> <div class="more-columns_column"><ul class="selection-list"><%= val3%></ul></div> </div> </script> <script type="text/template" id="facet-more-terms-div"> <div class="more-columns_container"> <div class="more-columns_column" id="<%= name%>-col1"><%= val%></div> <div class="more-columns_column" id="<%= name%>-col2"></div> <div class="more-columns_column" id="<%= name%>-col3"></div> </div> </script> <script type="text/template" id="facet-more-terms-list"> <ul class="selection-list"><%= val%></ul> </script> <script type="text/template" id="search-result-facet-more"> <a id="more-<%= name %>" href="#" class="sidebar_more white">More</a> </script> <script type="text/template" id="search-result-facet-detail"> <a href="#" id="details-link-<%= id %>" class="sidebar_more black">details</a> <ul id="details-container-<%= id %>" class="list-unstyled" style="display:none;" data-value="<%= valName %>"></ul> </script> <script type="text/template" id="search-result-facet-value"> <li class="sf-list_list-item <%= rowclass %>" style="<%= display %>"> <input type="checkbox" class="sf-list_input <%= boxstyle %>" name="chkFacet-<%= name %>" value="<%= code %>" aria-label="<%= dataValue %>" data-value="<%= dataValue %>" id="<%= id %>" <%= checked %> acronym="<%= acronym %>" /> <% if (hasCloseButton === true) { %> <div <% if (isbold != '') { %> class="sf-list_label sf-authors-bold" <% } else { %> class="sf-list_label" style="margin-bottom:5px"<% } %>><%= valName %><span class="facet-count"><%= valCount %></span> <span class="fal fa-times-circle facet-value_toggle purple-color"></span></div> <%= detail%> <% } else { %> <label <%= title%> for="<%= id %>" <% if (isbold != '') { %> class="sf-list_label sf-authors-bold" <% } else { %> class="sf-list_label" <% } %>><%= valName %> <span class="facet-count"><%= valCount %></span></label> <%= detail%> <% } %> </li> </script> <script type="text/template" id="more-term-facet-value"> <li class="selection-list_list-item" style="<%= display %>"> <input id="<%= labelid %>" class="selection-list_checkbox" type="checkbox" name="<%= name %>" data-value="<%= dataValue %>" <%= checked %> <%= boxstyle %>/><div class="selection-list_link" name="text-<%= name %>" data-value="<%= dataValue %>" <%= clazz %>><label for="<%= labelid %>" style="font-weight:normal;margin-bottom:0px;"><%= valName %><% if (valCount != "") { %> <span class="more-facet-count"><%= valCount %></span><% } %></label></div><% if (isx === true) { %><a href="#" aria-label="selection expander" class="selection-list_expander <%= inputname%>-expandin"><svg class="selection-list_arrow"><use xlink:href="#right-arrow" /></svg></a><% } %> </li> </script> <script type="text/template" id="more-term-selected"> <div class="selected-facet" data-topic="<%= finalTopic %>"> <%= val %> <a href="#" name="selected-x" aria-label="<%= dataValue %>" data-value="<%= dataValue %>" count="<%= cnt %>" class="selected-facet_close" ><span class="fal fa-times-circle purple-color"></span></a> </div> </script> <script type="text/template" id="search-result-facet-class"> class="" </script> <script type="text/template" id="search-result-facet-style-normal"> style="font-weight:normal" </script> <script type="text/template" id="search-result-facet-sort-popup"> <p> <input type="radio" id='<%= name %>:item-order:ascending' name="facetSortBy" value='<%= name %>:item-order:ascending' > <label for='<%= name %>:item-order:ascending'><%= label %> ascending</label><br> <input type="radio" id='<%= name %>:item-order:descending' name="facetSortBy" value='<%= name %>:item-order:descending' > <label for='<%= name %>:item-order:descending'><%= label %> descending</label><br> <input type="radio" id='<%= name %>:frequency-order:ascending' name="facetSortBy" value='<%= name %>:frequency-order:ascending' > <label for='<%= name %>:frequency-order:ascending'>Frequency ascending</label><br> <input type="radio" id='<%= name %>:frequency-order:descending' name="facetSortBy" value='<%= name %>:frequency-order:descending'> <label for='<%= name %>:frequency-order:descending'>Frequency descending</label> </p> </script> <script type="text/template" id="filter-selected"> <li class="label filter-tag filter-tag--<%= filterType %>"> <%= filterValue %> <a class="inline-dismiss"><span name="filterSelected" id="<%= filterId %>" class="fal fa-times purple-color" data-value="<%= filterValue %>"></span></a></li> </script> <script type="text/template" id="filter-search"> <li class="filter-search label filter-tag filter-tag--<%= filterType %>"> <%= filterLabel %> <a class="inline-dismiss"><span name="filterSelected" id="<%= filterId %>" class="fal fa-times purple-color" data-value="<%= filterValue %>"></span></a></li> </script> <script type="text/template" id="publication-sort-template"> <button class="sf-sort-toggle"><i class="fas fa-sort"></i><span class="sr-only">sort</span></button> <div class="sf-sort-popup"> <ul> <li class="active"><a href="#" name="sort-<%= type%>" data-value="<%= type%>:frequency-order:descending">Article Count</a></li> <li><a href="#" name="sort-<%= type%>" data-value="<%= type%>:item-order:ascending">Alphabetical A>Z</a></li> <li><a href="#" name="sort-<%= type%>" data-value="<%= type%>:item-order:descending">Alphabetical Z>A</a></li> </ul> </div> </script> <script type="text/template" id="author-topic-sort-template"> <button class="sf-sort-toggle"><i class="fas fa-sort"></i><span class="sr-only">sort</span></button> <div class="sf-sort-popup"> <ul> <li class="active"><a href="#" name="sort-<%= type%>" data-value="<%= type%>:frequency-order:descending">Article Count</a></li> <li><a href="#" name="sort-<%= type%>" data-value="<%= type%>:item-order:ascending">Alphabetical A>Z</a></li> <li><a href="#" name="sort-<%= type%>" data-value="<%= type%>:item-order:descending">Alphabetical Z>A</a></li> </ul> </div> </script> <script type="text/template" id="year-sort-template"> <button class="sf-sort-toggle"><i class="fas fa-sort"></i><span class="sr-only">sort</span></button> <div class="sf-sort-popup"> <ul> <li class="active"><a href="#" name="sort-year" data-value="year:item-order:descending">Newest date first</a></li> <li><a href="#" name="sort-year" data-value="year:item-order:ascending">Oldest date first</a></li> <li><a href="#" name="sort-year" data-value="year:frequency-order:descending">Article Count</a></li> </ul> </div> </script> <script type="text/template" id="more-pop-up-template"> <%= values%> </script> <script type="text/template" id="loading-gif-template"> <li><img style="position:center; display:none;" src="../images/ajax-loader.gif"/></li> </script> <script type="text/template" id="all-plus-separator-template"> <li class="sf-select-all"><input id="<%= allId %>" type="checkbox" > <label for="<%= allId %>">All</label></li> </script> <script type="text/template" id="more-topic-column-header"> <div class="selection-list_header"><%= name %></div> </script> <script type="text/template" id="loader"> <div class="progress"> <div class="progress-bar progress-bar-striped active" role="progress-bar" id="progress-<%= allId %>"></div> </div> </script> <script type="text/javascript"> $(document).ready(function() { if (location.hash.indexOf("figanchor") != -1) { let figHash = location.hash; $("#figurestablink").click(); window.location.hash = figHash; $(location.hash).get(0).scrollIntoView({behavior: "smooth"}); } $.get('/checkjs.cfm?s=KKHJ2M2'); populateRecentPages(); $("img").removeClass("lazyimg").unveil(100); }); </script> <script type="text/javascript"> var gaAcct = "UA-1200622-15"; function downloadJSAtOnload() { var element = document.createElement("script"); 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