There can indeed be differences in fiber optic cables. The question is
whether or not these differences will affect the sound. (I worked in the
telecommunications and broadacst industries for many years teaching, amongst
other things, fiberoptics.)
The differences between "quality" and lesser cables will usually be
mechanical, but this is not limited to quantification of strength. The
problem with cables of poor quality may be their alignment within the
connector housing. If the cables are misaligned, then the level of optical
signal will go down. At some point, when the received signal is attenuated
far enough, the bit error rate (BER) of the signal begins to increase and
artifacts begin to show up in the recovered signal. Exactly what the
receiving device does with digital signals in which there is a significant
BER, depends upon the digital circuitry within the device.
Another issue is that the fibre simply does not make a close coupling with
the receiving diode because it is too far back in the housing. One of the
demonstrations I used was to slowly attenuate the optical signal by pulling
the cable out and watching the BER meter, at the same as listening to the
recovered audio. Indeed, at some point the audio will become distorted and
eventually disappear.
Now will this in reality affect your audio signal? Attenuation of the
optical signal due to misalignment or poor coupling might be a problem, but
at the distances involved in out systems, there is plenty of overhead and it
shouldn't have any affect. Additionally we are talking about our multimode
optical cable, and alignment is simply not as critical as with the
long-distance, high-bandwidth singlemode cables that are used in the
broadcast and telecom industries.
If you are really anal about all of this, then run this test: play through
the optical cable and listen carefully as you slowly pull the optical
connector (either end will do) out of the receptacle. You will probably be
able to get a tenth of an inch out before you begin to lose the signal,
maybe more. If you are getting a signal when you start this little test and
you can move the connector out even a little and still get a signal, then
you have enough optical power getting to the receiver.
If you are really, really concerned, then you can always clean the ends of
the cable with denatured alcohol. (Send pictures - I'd like a good laugh.)
What this all really means is that you shouldn't worry about it. Enjoy the
music.
Iechyd da (that's "good health" in Welsh),
Grover Cleveland
www.llareggub.com
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