How Do a CW Laser, an EOM, and an APD Generate a QKD Key?
Follow a consistent phase-encoded decoy-state BB84 example from two-bin states and SPAD events to authenticated processing; distinguish detection, QBER and finite-key security.
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Latest postsMore posts
What Is an Eye Diagram? Why Measure It, and How to Read the Signals Inside
See how clock-aligned waveforms form an eye, compare noise, jitter and ISI on common scales, and read eye height/width with stated statistical rules. Eye appearance alone does not establish BER.
How to Read Specialty Fiber Specifications?
Four figures connect specialty-fiber structures to PM alignment, double-clad pumping and effective mode area. Distinguish physical core size, MFD, pump-launch channels and M², and read named-product specs with their test conditions.
How Does an Optical Scale Measure to the Nanometer?
How relative grating displacement becomes quadrature signals and a fine output step: connected transmission optics, grating overlap, sine/cosine phase and interpolation. Distinguish signal period, grating period, resolution and accuracy.
Electro-Optic Modulators (EOM): MZ, Micro-Ring, and Emerging Technologies
Separate EOM mechanisms, MZ/ring readout structures and material platforms. Compare demonstrated rates with their format, bias, BER/FEC criteria and energy boundary.
Data Rate vs Bandwidth: What Is the Actual Relationship?
Separate bit/s, baud and Hz, then examine pulse shaping, PAM4 levels and Shannon capacity. Distinguish nominal Ethernet rates, raw coded line rates and real-link conditions.
Editor's picks
What's Inside a Modern Optical Transceiver Module?
An optical transceiver is the standardized interface between switches and fiber: transmitter (laser + driver + modulation), receiver (photodetector + TIA + DSP), the IM-DD and coherent routes, SFP-to-OSFP packaging, and silicon-photonics integration. This article breaks down the full architecture of a modern module.
How Do High-Power Fiber Lasers Keep Diffraction-Limited Beam Quality?
The core question of high-power manufacturing lasers: how to keep near-diffraction-limited beam quality at kilowatt-level power. The answer is MOPA — the seed sets beam quality, the amplifier sets power, and the two are decoupled; combined with multi-stage Yb-doped fiber amplification, pump combining, and isolators, verified with a concrete JPT optical path.
Optical communicationsMore posts
What Is an Eye Diagram? Why Measure It, and How to Read the Signals Inside
See how clock-aligned waveforms form an eye, compare noise, jitter and ISI on common scales, and read eye height/width with stated statistical rules. Eye appearance alone does not establish BER.
How to Read Specialty Fiber Specifications?
Four figures connect specialty-fiber structures to PM alignment, double-clad pumping and effective mode area. Distinguish physical core size, MFD, pump-launch channels and M², and read named-product specs with their test conditions.
Electro-Optic Modulators (EOM): MZ, Micro-Ring, and Emerging Technologies
Separate EOM mechanisms, MZ/ring readout structures and material platforms. Compare demonstrated rates with their format, bias, BER/FEC criteria and energy boundary.
Electromechanical controlMore posts
How Does an Optical Scale Measure to the Nanometer?
How relative grating displacement becomes quadrature signals and a fine output step: connected transmission optics, grating overlap, sine/cosine phase and interpolation. Distinguish signal period, grating period, resolution and accuracy.
Why Is a Voice Coil Fast and Smooth?
How a voice coil creates axial force, why a carriage still needs guidance, how coil/field overlap sets useful travel, and why sustained force causes heating.
Why Can Direct Drive Reach Sub-Micron?
A linear motor applies force directly to the carriage with no screw in between, eliminating lead error and backlash; positioning precision is then set by the optical linear encoder and rails, so it can reach sub-micron. A coreless mover avoids detent force and is smoothest; an iron-core mover gives more force but has cogging. The cost is higher price, mover mass affecting acceleration, and a magnetic field that needs shielding.
LasersMore posts
Why Is the VCSEL the Workhorse Laser of Short-Reach Data Centers?
The vertical cavity (two DBR mirrors) lets VCSELs be tested at wafer level and built into arrays; combined with the 850 nm multimode ecosystem, that makes them the most economical short-reach data-center laser. This article breaks down the structure, manufacturing advantages, mainstream wavelengths, and reach limits.
Why Does Optical Communication Need Three Kinds of Lasers — FPLD, DFB, and EML?
Cavity structure sets spectral purity; modulation method sets speed. FPLD is cheapest but multimode, DFB is the stable single-mode workhorse behind WDM, and EML integrates a high-speed modulator on one chip. Together they form a cost × speed ladder, each matched to different links.
How Do High-Power Fiber Lasers Keep Diffraction-Limited Beam Quality?
The core question of high-power manufacturing lasers: how to keep near-diffraction-limited beam quality at kilowatt-level power. The answer is MOPA — the seed sets beam quality, the amplifier sets power, and the two are decoupled; combined with multi-stage Yb-doped fiber amplification, pump combining, and isolators, verified with a concrete JPT optical path.
Mechanical machiningMore posts
Why Can't Chip Patterns Be Milled?
Turning, milling, and drilling all cut with a pre-made edge — and the limit is not "sharpen the tool a bit." Tool-nose radius sets the ripple, edge radius sets the minimum chip, temperature makes the machine itself grow, and a silicon atom spacing is about 425,000 times smaller than a 0.1 mm end mill. Chip patterns and EUV optical surfaces are therefore not made by cutters.
What Do the 10 μm and 1 μm on a Drawing Actually Measure?
A drawing that says 10 μm or 1 μm is asking about the finished part. ISO 230-2 positioning accuracy A describes a single axis only: an uncompensated 3-axis miller measured 20–33 μm on X; after compensation single-axis A fell to 1.3–1.7 μm while the two-axis ballbar positioning tolerance stayed around 10–13 μm. This article maps the two tolerance levels onto two published machine tests.