Key takeaways
- Optical tops out at Dolby Digital 5.1 and DTS 5.1, both compressed formats, and never carries Dolby Atmos or DTS:X regardless of how capable the soundbar is.
- HDMI ARC adds Dolby Digital Plus, the format behind streaming Atmos, while eARC adds the lossless Dolby TrueHD and DTS-HD Master Audio a 4K Blu-ray disc actually stores.
- Optical carries no control signal at all, so a soundbar connected that way never shares a single remote with the TV the way an HDMI ARC connection can.
- A plastic TOSLINK cable reliably runs to about 5 metres before signal loss becomes a real risk, shorter than most HDMI cables are expected to handle.
- Optical remains the right choice for a TV with no ARC or eARC port at all, not a downgrade chosen out of ignorance.
Optical carries a compressed 5.1 signal down a strand of light and stops there. HDMI’s ARC and eARC carry everything from stereo up to a disc’s own lossless, object based Atmos track, over the same cable already connected to your gear.
Both still exist on plenty of televisions sold today, and plenty of readers are choosing between the two right now because their soundbar came with both cables in the box. Four differences decide which cable actually belongs in that port: format ceiling, the physical cable itself, remote control, and which older televisions still genuinely need the optical option.
The format ceiling each connection hits
Optical, also called TOSLINK, tops out at Dolby Digital 5.1 and DTS 5.1, both compressed formats developed for the DVD era. It has no bandwidth for Dolby Digital Plus, the format behind streaming Atmos, and none at all for the lossless or object based metadata that Atmos and DTS:X depend on.
HDMI ARC adds Dolby Digital Plus on top of everything optical offers, which is exactly how Netflix, Disney Plus, and most streaming Atmos mixes reach a soundbar. HDMI eARC goes further still, adding the bandwidth for lossless Dolby TrueHD and DTS-HD Master Audio, the formats a 4K Blu-ray disc actually stores its Atmos or DTS:X track in.
| Connection | Carries Atmos | Format ceiling |
|---|---|---|
| Optical | No | Dolby Digital 5.1, DTS 5.1 |
| HDMI ARC | Streaming only | Adds Dolby Digital Plus |
| HDMI eARC | Streaming and disc | Adds Dolby TrueHD, DTS-HD Master Audio |
The Dolby technology overview covers how the format’s object based approach depends on that extra bandwidth existing somewhere in the chain. For the fuller breakdown of ARC and eARC specifically, see eARC versus ARC, what changes.
DTS:X follows the same pattern as Atmos on this point. Streaming DTS:X arrives compressed, while a disc’s DTS:X track rides on DTS-HD Master Audio, a lossless format optical was never built to carry. The DTS technology page covers the format’s own object based approach in more depth.
Glass fibre versus copper: the physical connection itself
A TOSLINK cable sends audio as pulses of light, usually a red LED around 650 nanometres, down a strand of plastic or glass optical fibre. It carries no electrical signal at all, which makes it immune to the electrical interference and ground loop hum that sometimes plagues copper connections.
That same fibre is also the weak point. A plastic TOSLINK cable reliably runs to about 5 metres before signal loss becomes a real risk, and the connector itself is a thin plastic tab that snaps if a cable gets yanked rather than unplugged properly. HDMI cables use copper conductors, tolerate rougher handling, and commonly run to 10 metres or more without needing an active repeater.
Cost tells a similar story. A basic TOSLINK cable runs about 5 to 15 USD for a 2 metre length, while a comparable certified HDMI cable costs roughly the same or slightly more, so price is rarely the deciding factor between the two once a TV actually offers both ports.
Bend a TOSLINK cable too sharply around a tight corner behind a TV stand and the signal can drop out intermittently long before the cable looks damaged from the outside. HDMI copper cables are far more forgiving of a tight bend.
Dust matters more with optical than most people expect. The transmitter and receiver are small exposed lenses at each end, and a cable left unplugged in a drawer for months can pick up enough dust to cause dropouts until both ends are wiped clean. HDMI’s pin connectors are comparatively unbothered by the same kind of neglect.
One remote or two: what CEC actually needs
Optical carries no control data whatsoever, only the audio signal itself. A soundbar connected by optical will never share a single remote with the TV, since there is no channel for HDMI-CEC commands to travel on.
HDMI ARC and eARC both carry CEC alongside the audio, which is what lets a single remote turn a TV on, wake the soundbar, and adjust volume together. If juggling two remotes every movie night is the actual complaint, the cable itself is only half the fix. The rest is covered in setting up HDMI-CEC correctly.
Some soundbars ship with a separate infrared learning remote specifically to paper over an optical connection’s lack of CEC, letting one remote control volume even without the HDMI handshake underneath it. It is a workaround, not the same thing as true CEC control.
CEC itself is not automatic even over HDMI. Both the TV and the soundbar need the feature enabled in their own settings menus, under whatever brand name each manufacturer has given it, before one remote actually takes over both devices.
Where each one still makes sense on an older TV
Plenty of TVs sold before around 2013, plus a good number of budget models since, have an optical output and no ARC or eARC port at all. For those, optical is not a downgrade chosen out of ignorance. It is the only digital audio path the TV offers, and it still delivers a clear improvement over the TV’s own built in speakers.
A customer with a twelve year old bedroom TV called wanting Atmos from a new soundbar, and the honest answer was that no cable was going to make that happen on that television. Optical still connected the same soundbar’s Dolby Digital 5.1 decoding cleanly, which was a real improvement over the TV speakers even without Atmos in the mix. For the fuller version of that conversation, see connecting a soundbar to an older TV.
Game consoles and older disc players without an HDMI ARC capable output also sometimes rely on optical as their only digital audio path, separate from the TV question entirely. In that case the connection is chosen by the source device, not by preference.
A soundbar’s own instruction manual usually lists both a preferred and a fallback connection method in order, and it is worth reading that page once rather than guessing. Manufacturers rank optical below ARC and eARC for a reason, and the manual will say so plainly.
The connection that fits your actual television
If the TV has a labelled ARC or eARC port, use it. HDMI carries everything optical does and considerably more, over a cable that is already more durable and already handles remote control convenience optical never can.
If the TV genuinely has no ARC or eARC port, optical is not a compromise worth feeling bad about. It still delivers clean 5.1 surround sound from broadcast television and most streaming apps, just never an Atmos or DTS:X badge, and no single remote across devices. That is a fair trade for a television that was never going to output a lossless or object based track in the first place.
- TV has a port labelled ARC or eARC: use HDMI, always
- TV has optical only: it is still a real upgrade over built in speakers
- Two remotes are the actual complaint: check CEC support before blaming the cable
- Watching mostly broadcast television or older discs: optical’s format ceiling is rarely the limiting factor
Buying a soundbar for its Atmos badge and then connecting it by optical wastes the exact feature being paid for. Check the TV’s actual ports before the purchase, not after the box is already open, since a returned soundbar over a cable mismatch is a completely avoidable trip back to the shop.
Questions readers ask about this
Most TVs allow both physically, but only one will actually be active for a given app or source at a time, chosen in the audio output settings menu. Running both rarely causes harm, though it adds clutter for no benefit once the HDMI connection is confirmed working.
Not for the audio itself, since both carry the same digital signal as pulses of light rather than an analogue waveform. Glass fibre mainly matters for reliability over longer runs, past roughly 5 to 10 metres, where plastic fibre becomes more prone to signal loss.
Optical carries no control signal at all, only the digital audio stream, so there is no channel for a remote's commands to travel on. Volume control over a single remote requires either the soundbar's own infrared learning function or an HDMI-CEC connection instead.
Not entirely, though it is increasingly treated as a secondary output behind ARC and eARC on mid range and flagship models. Budget television lines and many computer monitors still ship with optical as the only digital audio option, so it remains relevant for several more years.
No. Optical's bandwidth caps out around Dolby Digital 5.1 or DTS 5.1, both six channel formats at most. A genuine 7.1 channel mix, compressed or not, needs an HDMI ARC or eARC connection to reach a soundbar or receiver intact.
About the author
Rahul Gupta
Rahul Gupta has spent nearly a decade quietly wiring living rooms, testing soundbars in every awkward apartment layout imaginable, and untangling the kind of HDMI handshake problems that make people give up on Atmos altogether. He writes here about what actually works when you get the boxes home—not what the spec sheet promises. If a piece of gear on this site earns a recommendation, it earned it in a real room with real furniture, not a lab.
