DCI Power Per Bit Has a Floor — And We're Hitting It

Every generation of coherent pluggables came with the same chart on the same slide. A clean descending curve, pJ/bit on the Y axis, time on the X axis. Forty pJ/bit in 2018. Twenty-eight in 2020. Eighteen in 2022.

Rene Fichtmueller / 2026-05-13 / ~3 min read

Build in Public Open Source Software Engineering Personal Developer Tools GitHub Transparency Community

Six Weeks of Building in Public: What Actually Happened

I started publishing everything I built six weeks ago. Eight repositories, zero marketing budget, one unexpected outcome: writing about the work changed how I do the work.

Rene Fichtmueller / 2026-05-13 / ~2 min read

ADHD Diary No-Travel-Day Mental Health Productivity Neurodivergent Rest Burnout Personal Building

ADHD Diary #004: The Week Nothing Shipped

No-Travel-Day. No commits, no launches, no progress visible to anyone outside my head. What a week of rest looks like when your brain doesn't know how to stop.

Rene Fichtmueller / 2026-05-12 / ~2 min read

Transceiver Compatibility Vendor Lock MSA Optical Networking TCO Network Engineering Cisco Juniper Open Source

Third-Party Optics: The Real Risk vs the Vendor Story

Cisco says third-party optics void your support contract. The MSA says otherwise. Here's what the standards actually guarantee, what vendor lock costs at scale, and how to run the risk-adjusted calculation.

Rene Fichtmueller / 2026-05-09 / ~2 min read

DSP Power Budget Coherent 400G Data Center TCO Network Design Optical Networking LPO Energy Efficiency

DSP Power: The Budget Item That Keeps Growing

A 400G coherent port draws 16–20W. At 64 ports per chassis: 1.3kW just for optics. DSP power is a real constraint in dense deployments — and most capacity plans ignore it.

Rene Fichtmueller / 2026-05-08 / ~2 min read

Coherent 400G 800G QSFP-DD OSFP OpenZR+ OpenROADM Optical Networking Pluggable Supply Chain

Pluggable Coherent in 2026: What's Shipping, What's Vaporware

800G ZR modules are announced. 1.6T is on the roadmap. Meanwhile, half the 400G ZR+ SKUs take 14 weeks to ship. Here's what's real in pluggable coherent today.

Rene Fichtmueller / 2026-05-07 / ~2 min read

Fiber Testing OTDR Optical Networking Data Center Network Operations Connector Contamination IEC 61300 FlexBox Flexoptix Network Engineering

Your OTDR Is Lying to You

An OTDR finds breaks, splices, and macrobends. It tells you nothing about the cause of 80% of optical link failures: contaminated connectors. Here's what actual fiber testing looks like — and how an SFP-based microOTDR changes the economics.

Rene Fichtmueller / 2026-05-06 / ~3 min read

400G Coherent ZR ZR+ DWDM Optical Networking WAN Network Design TCO OpenZR+ OpenROADM

400G ZR vs ZR+: You're Asking the Wrong Question

The ZR vs ZR+ debate dominates every WAN discussion. It's the wrong frame. The real question is whether you understand your link budget well enough to buy either.

Rene Fichtmueller / 2026-05-05 / ~2 min read

DWDM Open Line System Optical Networking 400ZR 400ZR+ Alien Wavelength Disaggregated ROADM EDFA Coherent Optics TIP Goldstone Hyperscale Network Architecture OSNR Spectrum Management

Open Line Systems — Breaking the DWDM Vendor Lock

Your DWDM line system and your transponders come from the same vendor. The amplifiers, the mux/demux, the management plane, the optics. One PO, one support contract, one vendor'

Rene Fichtmueller / 2026-05-01 / ~4 min read

Silicon Photonics Indium Phosphide Optical Networking SiPh InP Photonic Integrated Circuit CMOS Coherent Optics Supply Chain Intel Cisco Lumentum Coherent Corp Foundry Semiconductor

Silicon Photonics vs Indium Phosphide — The Foundry War Behind Your Optics

Two materials. Two manufacturing ecosystems. Two different bets on the future of optical networking. The choice between Silicon Photonics and Indium Phosphide determines who can build your optics, how fast,

Rene Fichtmueller / 2026-04-30 / ~3 min read

// about the author

Rene Fichtmueller

Social Networker

20+ years building and breaking networks. Optical transport, peering, data center infrastructure. Writing about the things that go wrong at 2AM — and how to prevent them.

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