GUIDE · UPDATED 2026
Data diode, controlled USB or optical transfer?
Once a laboratory decides an instrument PC must stay isolated, the next question is how files leave it. Three routes come up in almost every discussion. They are not competitors in every case: they solve different volumes and different frequencies.
Written by Taha Bayar, a biologist working on laboratory data handover. Kionel sells one of the options below; the comparison is meant to be usable even if you choose another.
Side by side
| Data diode | Controlled USB | Optical (screen to camera) | |
|---|---|---|---|
| Best for | Continuous one-way flow between two networks | Any size, occasional | Small files, occasional or daily |
| Installation | Hardware, network changes, IT project | Media, scanning station, procedure | A browser on each device |
| Physical media | None | Yes — the thing policies try to remove | None |
| Record of each transfer | Depends on the software around it | Depends on logs and people | Two signed records per transfer |
| Throughput | High | High | Low: kilobytes per second |
| Main weakness | Cost and effort for a few files a week | Malware and lost media; weak audit trail | Needs cameras allowed on site; small files only |
How to choose
- Large or continuous data (raw spectra, images, streaming instrument output): a data diode or a controlled network route. Optical transfer is too slow.
- Occasional files of any size, and USB is already controlled well: keep it. Add a written record of each transfer if an inspector has asked for one.
- Small files, several times a week, and the finding is "no audit trail": optical transfer with signed records is the cheapest route that answers that finding without new hardware.
The question an inspector asks
Whatever the route, the question is the same: after the file moved, what can you show? Who sent which file, bound to which work order, and did the receiving side get exactly those bytes? A route that answers that with a document you can hand over is worth more than a faster route that answers it with memory.
A fourth route: a one-way serial cable
Between a diode and a camera sits a cable: a serial line with the return wire left out. Nothing can travel back, it needs no camera, and at 80 KB/s it is several times faster than optical transfer. It suits a fixed instrument PC next to the computer that feeds the LIMS. Wiring, speeds and limits.
Where Kionel fits
Kionel is the optical route, and it also sends over a one-way serial cable. It runs in a browser, needs no installation on the instrument PC, and produces a signed dispatch record and a signed delivery receipt for every transfer. It has not had an independent security audit yet and does not sanitise file content — if either matters for your decision, the security page lists the current status.
Try it on your own bench
Kionel is free and open source (AGPL-3.0): it moves files up to 64 MB between two of your devices, end to end, with signed records and reports. Nothing is uploaded.
Start free What Kionel does not protect
If the file has to stay on a USB stick, the same two signed records can be made around it: keep the USB stick, add the proof.