Dragon's Den - Analogue Optical Guitar Cable

[gapiro]

[quote name='EBS_freak' timestamp='1470314925' post='3105034']
I originally thought that too - although I suspect that ship has set sail already. Any company wanting that sort of channel count is going to be in the realm of digital - so a couple of cat5s does the job - at a significantly cheaper price also.
[/quote]
Indeed - although my thoughts are that it may be suitable for conference centres etc - places where there are likely to be permanently wired in fixtures?

[440Hz]

[quote name='opticfibre' timestamp='1470311916' post='3104986']
The frequency of the LED isn't changing just the brightness.

Some people will say AM amplitude as its the amplitude of the light.
people assume we are transmitting a frequency i.e 100khz and changing the intensity of the 100khz and modulating the signal on that.. but we don't transmit a frequency. The 660nm is just the frequency of RED light, but i see your point about 660nm being the carrier frequency and us changing the amplitude of it.

Its similar to when we say optical, people assume its digital, Peter Jones assumed we were encoding and decoding.
[/quote]


To avoid confusion 660nm is the wavelength of the light not the frequency, as the wavelength gets shorter the colour changes by the time it has roughly reached 2/3 of it original length it is BLUE rather than RED.

Wavelength multiplied by Frequency = the speed of light

The speed of light is around 300 000 000 metres per second
Thus the original BBC Light Programme* (No Pun intended) was on a wavelength of 1500m
dividing this into the speed of light gives 200 000Hz or 200kHz
Similarly for 660nm we get 454,545,454,545,455 Hz or 454THz which is the carrier frequency which is then Intensity or Amplitude Modulated.

Since LEDs and Photo-diodes combinations result in a photo-diode current proportional to the LED current then if the LED current is proportional to the amplitude of the signal voltage the system will be fairly linear.

Note that the speed of light through a fibre optic cable is slower than the speed of light through a vacuum because the light does not travel straight but is constantly being refracted and bounced off the internal edges of the fibre thus taking a longer path at the actual speed of light giving an apparent speed which is lower.
In practice, it is around 200 000 000 metres per second. The speed of light divided by this apparent speed is known as the refractive index of the cable and is around 1.5.

* Transmitter now changed to 198kHz (to meet new regulations for 9kHz channel spacing) and used for BBC Radio 4.

Edited August 4, 2016 by 440Hz

[4stringslow]

[quote name='TimR' timestamp='1470302330' post='3104840']
That would only transmit the frequency data though wouldn't it? Everything would just be at the same volume.
[/quote]
Sorry, I missed this earlier question.

PFM would switch the light source on and off at a frequency proportional to the analogue input voltage. The receiver would use a Phase-Locked Loop to lock to the received signal (the on/off frequency, not the light frequency) and recover the analogue audio waveform. Solves the problem of AM linearity but it could be argued that transmission is digital because it is achieved by the on/off switching of the light rather than the brightness. In fact, given a minimum brightness for the link to work, the actual brightness of the light is irrelevant, which confers other advantages such as being almost immune to cable length attenuation effects or 'microphony' effects when cable is kinked or crushed or generally disturbed - though such effects are far less of an issue with a large plastic fibre than with a mono mode glass fibre.

[spectoremg]

[quote name='opticfibre' timestamp='1470311322' post='3104983']
My Pleasure to join, took a couple of days to get approved by the admin

Don't think i should compare basschat to guitarchat
[/quote]Welcome.
You may be tempted by topics about Paul McCartney, Mark King, Lemmy and someone called Jaco Pastorius. Also posts about amplification which may appear ostensibly technical but are just a front for some micro-comparison nob twiddling or just plain dick measuring. Avoid. Topics about song choice also. And don't be tempted to buy a 15-string bass.
And if you see the word HEFT, shut your computer down immediately!

[TimR]

and don't mention the Beatles or Milwaukee.

[lojo]

I think we would all love to know what model guitar/bass you have in you lab

Cynicism aside, I'm sure we all wish you good luck with the business and well done for winning your pitch

[AttitudeCastle]

[quote name='opticfibre' timestamp='1470310199' post='3104961']
Hi Guys!

Its looks like the most popular question here is How do we do it?
The answer is simpler than you might think, and may cause a lot more questions from you.

We use IM to send the analogue optical signal Intensity Modulation not AM or FM or PWM or...

[url="https://en.wikipedia.org/wiki/Intensity_modulation"]https://en.wikipedia...sity_modulation[/url]
when the voltage signal goes up, our light goes up, when the voltage signal goes down our light goes down.

Our wavelength is 660nm but i don't think that's important, the reason we use 660nm is because the bespoke optical fiber we use is most sensitive in that range.

Hope this helps
[/quote]

Hello, and welcome to the forum! Always wonderful seeing companies pop in here, there a few floating around, and we all really appreciate it!

Hope we haven't all sounded too scathing, but that's just what we're all like We're a dour bunch, but we're fun, honest!

Won't launch into some questions here, but I'm excited to try our the product if possible some day soon enough.