Quick answer: An optical HDMI cable has a transmitter plug and a receiver plug, and the arrows on the shell are not decoration: reverse them and the screen stays black. Rated at 18 Gbit/s, most stock carries 4K at 60 Hz with 4:4:4 chroma. Expect AU$50 to AU$120 for 10 m to 15 m, and treat 20 mm as the minimum bend radius. A reversed lead shows nothing at all rather than a poor picture, and a tight fold in the jacket will kill the link within months.
The lead is installed, the television reports no signal, and the same lead works on the bench when it is turned around. Direction is the first thing to check on an optical assembly, before firmware, before receiver settings and before a second trip up the ladder. Check direction first, and most of these no signal faults disappear before a return visit.
Reading the Arrows on the Plugs
Source and display ends
Inside an optical lead the source plug converts the electrical signal to light and the display plug converts it back. The two ends are not interchangeable, and the electronics differ. A shell marked Source at one end and Display at the other tells you which end goes to the receiver and which goes to the panel.
When the markings are missing
Some brands mould a small arrow pointing away from the source, and a few print nothing at all, which is reason enough to avoid that stock. If the marking has worn off, test the lead on a short bench run in both orientations before it goes above a ceiling.
4K60 With Full 4:4:4 Chroma
What subsampling removes
4:4:4 chroma keeps full colour resolution, so red text on a dark background stays sharp. 4:2:0 halves the colour data and softens exactly that text. At 4K60 with 8-bit colour, 4:4:4 needs about 17.8 Gbit/s, which sits just inside the 18 Gbit/s ceiling of HDMI 2.0.
What the rating must say
The margin is thin, so an optical lead rated at 18 Gbit/s has to meet it in practice. Stock quoting 10.2 Gbit/s is describing HDMI 1.4 and will force 4:2:0 or 4K30. An active HDMI cable at 18 Gbit/s is the minimum for full chroma at 4K60, whatever the length.
Bend Radius, Coils and Service Loops
The bend that breaks the fibre
Glass breaks at a bend radius below about 10 mm and plastic fibre clouds. A 20 mm minimum suits both, which is roughly the curve of a tennis ball. A lead forced around a sharp stud or a tight cable clip fails at that point, often months after the install.
Storing the spare length
Store spare length in a loose figure of eight rather than a tight coil, and never wind an optical lead around your hand. If the path needs 12 m, buy 15 m and lose 3 m in loops rather than buying 12 m and stretching the run.
Where an Optical Lead Loses to Copper
Below 5 m, copper is cheaper and just as good at 4K60, and it survives rougher handling. Between 5 m and 10 m the two are close, and above 10 m the optical lead is the only reliable passive option. Compare at the length you actually need rather than at the shortest length on the page.
| Length | Rate | 4:4:4 at 4K60 | AUD price band |
|---|
| 5 m | 18 Gbit/s | Yes | AU$25 to AU$45 |
| 10 m | 18 Gbit/s | Yes | AU$50 to AU$85 |
| 15 m | 18 Gbit/s | Yes | AU$65 to AU$120 |
| 20 m | 18 Gbit/s | Yes | AU$90 to AU$150 |
| 30 m | 18 Gbit/s | Yes | AU$120 to AU$200 |
The HDMI cable rating breakdown helps here, because a 48 Gbit/s copper lead at 2 m costs less than an 18 Gbit/s optical lead at 15 m and does more work at that distance.
Ordering an Optical Lead That Fits
Order by length, rate and connector orientation, then add a spare if the run sits inside a wall. The fibre optic HDMI cable range lists direction marks and rated bandwidth per length, which is what an installer needs before quoting a job.
Send the run length, the source device and the display resolution to zongcarrie@zh-zong.com or call +86 13543026126. We will confirm rate, direction and plug type, then quote in AUD with freight to Sydney, Melbourne, Brisbane, Perth or Adelaide.
Practical scenarios
- Situation: A weatherboard house in Brunswick runs a 4K60 feed to a rear room television 8 m away. What to do: Use a 10 m optical lead rated at 18 Gbit/s and tape the source plug before the pull starts.
- Situation: A North Sydney boardroom has a ceiling projector 14 m from the table box. What to do: Order 15 m, leave 300 mm loops at both ends and test 4:4:4 before the ceiling tiles go back.
- Situation: A Perth apartment hides the receiver in a cupboard 2 m from the television. What to do: Stay with a 2 m copper lead, since optical adds cost and a direction rule with no benefit there.
- Situation: A Cairns hotel refurbishment reuses an optical lead from a storeroom with no markings. What to do: Test both orientations on the bench and discard it if either end shows sparkle at 4K60.
FAQ
What happens if an optical cable is plugged in backwards?
Nothing. The display gets no signal because the transmitter feeds the wrong end. No damage occurs, so swap the plugs and test again. If the picture then appears, the lead is fine and the installation note was the only problem.
Do optical leads support ARC or eARC?
Most do not, because audio return needs a path back to the source. A few designs include it and say so on the pack. If the television must send audio to a receiver over the same lead, confirm ARC or eARC support in writing before buying.
Can an optical lead bend around a corner?
A gentle sweep is fine, a sharp fold is not. Keep the radius above 20 mm, use a wide clip or a conduit sweep, and never press the jacket against a metal stud. Leads that fail usually fail at exactly that point.
