In this episode, Shahriar takes an in-depth look at the design and architecture of optical HDMI cables, which significantly extend the reach of traditional HDMI 2.0 twisted-pair copper links at a low cost.

The fundamentals of HDMI high-speed data transmission are explored, with a focus on the TMDS (Transition Minimized Differential Signaling) standard. The challenges of transitioning from twisted pairs to optical lanes are examined, highlighting the role of VCSELs and PIN photodiodes. Optical modules are analyzed in detail, emphasizing free-space optics and optical confinement techniques used with lasers and detectors. The received high-speed lane's eye diagram is captured, and the VCSELs' optical wavelength is confirmed to be 850 nm.

Additionally, the TX (driver) and RX (TIALA) chips are inspected under a microscope, revealing the VCSEL and photodetector arrays. The overall electronic architecture is then discussed in greater detail.

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In this episode Shahriar takes a look at a terahertz characterization technique using a Fabry-Perot resonance chamber made by EM Labs:

https://www.emlabs.jp/en/1-8-fpr.php

The chamber is able to measure dielectric constant and loss tangent with remarkable accuracy and prevision, ideal for materials with tan δ (Df) of 0.01 or less. This tutorial and review video is organized as follows:

00:00 – Introductions
00:45 – Dielectric Constant theory, equations and practical importance
04:54 – Measurement techniques using S-Parameters and resonance chambers
08:16 – Fabry-Perot resonator techniques for accurate Dk & Df measurements
11:04 – THz measurement setup including Fabry-Perot resonator, Keysight Streamline VNA and VDI frequency extenders
13:36 – Design challenges and features of the EM Labs Fabry-Perot resonator
16:02 – Software setup, resonator calibration and preparations
19:22 – Preparing, aligning and measuring samples, organic PCB laminate and prepreg
23:19 – Measuring ultra-low loss materials in J-Band
24:21 – Analyzing anisotropic material properties as a function of orientation
26:27 – Concluding remarks

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