Steve Conner wrote ...

I don't know of any FPGA cheaper than about £10. Certainly none with the required hardware to pump out 1Gb/s serial data streams. You need something like a Spartan-6 before you get that.

One possible cost saving of a FPGA would be to use the same FPGA as both the fibre optic receiver and Tesla coil driver.

One way to look at this is that two second-hand gigabit SFPs for say £10 each, plus four serdes chips at £10 each, plus a duplex patch cord (another £10) give you 24 channels of digital IO in both directions for a total cost of £70. About £3 per channel. So if you actually need all those channels, this is a cost-effective way to get them. The traditional fibre link used with Tesla coils costs about £40 and delivers one channel.

The sampling rate on the digital IO is fast enough (25MHz IIRC) that you could use each digital IO line for almost anything. Interrupter pulses, MIDI, RS232, SPI, I2C, PWM or whatever.

If that is too expensive for you then try the Teslink project described here. Fewer channels but cheaper, assuming you already have a PIC programmer or are prepared to make your own JDM-style one. No fancy 4 layer board is needed, all the components are available in DIP packages, so you could probably build it on stripboard.