| Electronics > Projects, Designs, and Technical Stuff |
| Plastic vs glass fiber TOSLINK? |
| << < (3/6) > >> |
| jaycee:
TOSLINK is designed to work with cheap plastic fibre, so single vs multimode is irrelevant. It's not even a laser - it's just a red LED being used! |
| Berni:
--- Quote from: Benta on March 28, 2019, 08:20:42 pm ---No difference. The signal is re-synchronized at the receiving end, jitter wouldn't make a difference. And why would glass be different from POF on jitter? Just a nice way of lightening your wallet. --- End quote --- Well that's not entirely true. The audio master clock is actually recovered from the SPDIF signal on the receiving end. This clock is used to decode the encoded data stream and to drive the DAC. So a bad noisy input signal could cause extra jitter on the master clock that can affect the DAC performance. That being said the reciever chip would only really have problems recovering a clean clock if the input signal is bad. Only form of signal deterioration on a fiber at these speeds is attenuation. So a glass fiber will only make a difference if you have a really long run of cable (Like 10 meters or more). Also when a receiver is right on the edge of having a usable signal it will likely start to cause bit errors, this can be clearly audible in the form of pops (Much like a dusty record). So if you can tightly wind the plastic cable (increasing attenuation) and not hear the pops then the receiver likely has enough signal strength to work with. For runs shorter than 5m this shouldn't be the case unless you have a crappy/damaged plastic cable. |
| mikerj:
--- Quote from: Benta on March 28, 2019, 07:51:55 pm --- --- Quote from: extide on March 28, 2019, 07:39:41 pm ---As long as it's getting enough signal to decode the data the sound quality should be identical (literally bit-perfect). The only real thing you need to worry about in scenarios like this is jitter, which should not be affected by the cable at all. --- End quote --- This. The TOSLINK interface is digital, so either you have connection or you don't. --- End quote --- Absolutely not true, this is the kind of gross oversimplification I would expect to see from the average layperson rather than on eevblog. SPDIF has no error correction (just a parity bit), if the link OSNR is degraded enough then multiple bit errors will occur and from experience they are very audible on an TOSLINK connection. |
| extide:
Well, then it doesnt have enough signal to decode the data properly, does it :) |
| TheUnnamedNewbie:
--- Quote from: extide on March 29, 2019, 03:27:50 pm ---Well, then it doesnt have enough signal to decode the data properly, does it :) --- End quote --- The thing is that you seem to make it sound so binary - either there is enough signal to decode the data, or there isn't. In reality, it is a more gradual process. As you get a lower SNR, you start getting a higher bit-error rate (BER). A BER of 10^-12 might be common for good links, but it slowly tapers down as you get more and more errors. The 'either it works or it does not' is true for things like WiFi (and ethernet, to some extent, which has error detection and re-transmit) where error correction will make you pretty much never receive wrong data - if the link works, what comes out is correct. In the case of SPDIF, you can have a high bit error rate while still getting something out of your receiver, and as a result take a hit in sound. |
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