Summary: <p>Optical communication 101 – learn about the basics of optics! <a href="http://www.twitter.com/Keysight_Daniel">Daniel Bogdanoff</a> and Mike Hoffman interview Stefan Loeffler.</p> <p>Video Version (YouTube):</p> <div class="jetpack-video-wrapper"></div> <p>Audio version:</p> <audio class="wp-audio-shortcode" id="audio-169-26" style="width: 100%;"><a href="https://eestalktech.com/wp-content/uploads/2017/05/optical-101-9.mp3">https://eestalktech.com/wp-content/uploads/2017/05/optical-101-9.mp3</a></audio> <h2>Discussion overview:</h2> <p>Similarities between optical and electrical</p> <p>Stefan was at <a href="http://www.ofcconference.org">OFC</a><br> What is optics? 1:21<br> What is <a href="https://en.wikipedia.org/wiki/Optical_communication">optical communication</a>? 1:30<br> There’s a sender and a receiver (optical telecommunication)<br> Usually we use a 9 um fiber optic cable, but sometimes we use lasers and air as a medium</p> <p>The transmitter is typically a laser<br> <a href="https://en.wikipedia.org/wiki/Light-emitting_diode">LEDs</a> don’t work for optical</p> <p>Optical fiber alignment is challenging, and is often accomplished using robotics</p> <p>How is optical different from electrical engineering?</p> <p>Photodiodes act receivers, use a <a href="https://en.wikipedia.org/wiki/Transimpedance_amplifier">transimpedance amplifier</a>. It is essentially “electrical in, electrical out” with optical in the middle.</p> <p>Optical used to be binary, but now it’s <a href="https://en.wikipedia.org/wiki/Quadrature_amplitude_modulation">QAM</a> 64</p> <p>Why do we have optical communication?<br> A need for long distance communication led to the use of optical.<br> Communication lines used to follow train tracks, and there were huts every 80 km. So, signals could be regenerated every 80 km.</p> <p>In the 1990s, a new o<a href="https://en.wikipedia.org/wiki/Optical_amplifier">ptical amplifier</a> was introduced.</p> <p><a href="http://www.keysight.com/en/pd-87792/optical-amplifier-test-solutions?cc=GB&lc=eng">Optical amplifier test solutions</a></p> <p>Signal reamplifcation vs. signal regeneration</p> <p>There’s a .1 dB per km loss in modern fiber optic cable 11:20<br> This enables undersea <a href="https://en.wikipedia.org/wiki/Fiber-optic_communication">fiber optic communication</a>, which has to be very reliable</p> <p>How does undersea communication get implemented?<br> Usually by consortium: <a href="https://en.wikipedia.org/wiki/I-ME-WE">I-ME-WE</a> <a href="https://en.wikipedia.org/wiki/SEA-ME-WE_5">SEA-ME-WE</a></p> <p>AT&T was originally a network provider</p> <p>What is <a href="https://en.wikipedia.org/wiki/Dark_fibre">dark fiber</a> (also known as dark fibre)?<br> Fiber is cheap, installation and right-of-way is expensive</p> <p>What happens if fiber breaks?</p> <p>Dark fiber can be used as a sensor by observing the change in its refractive index</p> <p>Water in fiber optic line is bad, anchors often break fiber optic cable 17:30</p> <p><a href="https://en.wikipedia.org/wiki/Optical_fiber_cable">Fiber optic cable </a>can be made out of a lot of different things</p> <p>Undersea fiber has to have some extra slack in the cable<br> Submarines are often used to inspect fiber optic cable</p> <p>You can find breaks in the line using OTDR – “Optical time domain reflectometry”</p> <p>A “distributed reflection” means a mostly linear loss. The slope of the reflection tells you the loss rate.</p> <p>The refractive index in fiber optic cable is about 1.5</p> <p>Latency and delay 23:00<br> The main issue is the data processing, not the data transmission</p> <p>A lot of optical engineers started in <a href="http://www.keysight.com/main/application.jspx?nid=-34787.0.00">RF engineering </a></p>
