Possibilities of working with Fiber: What can I use it for?

[LoveLaika]

I recently had a look at Sparkfun, and I found that they offered an experimental industrial fiber-optics kit. I posted some links below about the kits, with one example application as a USB-to-Serial communicator via fiber. Now, at first glance, it seems pretty cool, and the way they made working with fiber seems pretty straightforward: looking at the breakout kit, just attach the cable and hook up the appropriate connectors. Digging deeper, I found myself at a loss on how to incorporate fiber optics into my circuits.

I guess what I'm trying to ask is how can people incorporate fiber-optics into their applications? Taking the serial communicator as an example, TX and RX are sent with fiber, but those are two individual signals only going in one direction. Can you use it with other communication standards like I2C and whatnot, or does fiber not work that way? It's just a method of communication, but what are the limitations of it?




https://learn.sparkfun.com/tutorials/industrial-fiber-optics-hookup-guide
https://www.sparkfun.com/products/17508
https://www.sparkfun.com/products/17509
https://www.sparkfun.com/products/17510

[Renate]

I was just thinking/talking about that 1mm plastic fiber and if anybody still made/sold it.

Still, the prices for the components seems a bit high.

Serial communication is a natural, RS-232, RS-422.
I2C since it usually runs on an open-collector bus is not a natural fit, although you could do it with 3 fibers or some processing.
I always thought that it would be cute to run RS-485 over a single fiber, but you'd need a beam splitter or else a half duplex transceiver.

The optical aspect is neat for remote nodes but when you have to run power over copper anyway?

[LoveLaika]

So, Serial Communication (RS-232, and RS-422), and not I2C. That's a start. With open-collector bus terminology, it looks like you need 3 terminals (the IC output, the open collector, and IC ground), so that's 3 fibers? If that's the case, taking I2C as an example, 2 fibers can be SCL/SDA, and you can just transmit power/ground through another method. Am I wrong?

 

[EEVblog]

So, Serial Communication (RS-232, and RS-422), and not I2C. That's a start. With open-collector bus terminology, it looks like you need 3 terminals (the IC output, the open collector, and IC ground), so that's 3 fibers? If that's the case, taking I2C as an example, 2 fibers can be SCL/SDA, and you can just transmit power/ground through another method. Am I wrong?

You don't connect the grounds, as that defeats one huge advantage of fibre which is electrical isolation.
e.g. Tek IsoVu high voltage probes
https://www.tek.com/isolated-measurement-systems

You just have a LED driver at one end and a photo transistor at the other end, designed to mimic the I2C open collector bus. The grounds of the transmitter and receiver are floating. Each end is it's own ground reference.

As for the number of fibres, yes, you would need one for each line to duplicate a basic interface like RS232 TX/RX, I2C, SPI etc. Otherwise you'd have to implement an converter that changes that to a single line serial system, and that gets tricky.