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Can cheap "glow" optical fiber (or other inexpensive materials such as aquarium air tubing, etc.) be used for low-tech low-speed optical communications using just simple discrete components, such as ordinary LEDs and photo-transistors? (and no fancy connectors). If so, over what distances and data rates (1 foot or 100M, 1 baud or 1 Mbit, etc.) might this work.

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  • \$\begingroup\$ What does aquarium tubing have to do with anything? I think you do need the fancy connectors though. \$\endgroup\$ – DKNguyen Oct 14 '19 at 19:45
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    \$\begingroup\$ Look up toslink \$\endgroup\$ – Voltage Spike Oct 14 '19 at 19:54
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    \$\begingroup\$ aquarium tubing would be good for pneumatic or hydraulic communication \$\endgroup\$ – jsotola Oct 14 '19 at 20:24
  • \$\begingroup\$ @hotpaw2 I think the implication is you can just buy a TOSlink cable rather than needing to build a cable. \$\endgroup\$ – DKNguyen Oct 14 '19 at 20:25
  • \$\begingroup\$ @hotpaw2 nope, a "cut off cable end" does work, see the toshiba document I linked to in my answer \$\endgroup\$ – Marcus Müller Oct 14 '19 at 20:42
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So, considering free-space optical communication does work, anything that conducts light better than free-space path loss should generally work.

Think, for example, of the optical variant of S/PDIF, TOSLINK: certainly not high-tech by any modern means, it's cheap plastic optical fiber, about 8Mb/s according to Toshiba. Transmitter is a rather boring LED, not a laser like in high-speed optical comms.

The receiver is usually a photodiode (phototransistors are typically slower) in reverse bias with a transimpedance amplifier opamp configuration.

You can use fancy connectors, but really: it's just important that enough of your TX light power enters the fibre in a tight angle. So, there's "connectorless" TOSLINK "plugs" where you can just push in your (straightly cut off) POF.

Just a general remark: haven't worked directly with one myself, but SFP and SFP+ transceivers for fiberoptical comms are pretty "dumb"; although they are meant for hundreds of megabauds to gigabauds, I know multiple people who just connect the data pins to 10 MHz sources to have distributed clocking in their living rooms.

Since your doing comms and want to save on the connector and optical transport complexity: don't save on the channel coding :) especially if latency is not that critical, a large interleaver + block code might simply hide any unreliability of your connectors, and of course a lot of noise in general.

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    \$\begingroup\$ The limitation in TOSLINK is not the plastic fiber (POF) but the LED-based transmitters. The same fiber is used in MOST (automotive fiber network) for 40 Mb/s. \$\endgroup\$ – The Photon Oct 14 '19 at 20:21

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