OCaml All the Way Down – How Jane Street Builds FPGA Designs [video]

Re:OCaml All the Way Down – How Jane Street Builds FPGA Desi... by detaro on Sunday September 30, 2018 @01:54PM (#18107320)

Speed of light in fibre is lower than speed of light in air, so you can beat fibre speed of light by building fast wireless networks.

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Re:OCaml All the Way Down – How Jane Street Builds FPGA Desi... by fileeditview on Sunday September 30, 2018 @02:06PM (#18107391)

Thanks. I just looked it up and really wasn't aware of the huge difference.

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Re:OCaml All the Way Down – How Jane Street Builds FPGA Desi... by diggerNick6771 on Sunday September 30, 2018 @03:37PM (#18107943)

It's not really the fibre that slows down the signal as much as the opto-electrical repeaters that relay the signal many times as it travels vast distances.

Light can only go a few km before it needs to be boosted

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Re:OCaml All the Way Down – How Jane Street Builds FPGA Desi... by datenwolf on Sunday September 30, 2018 @05:08PM (#18108429)

This is wrong on both accounts.

The speed of light in a fiber is only about 70% of speed of light in vacuum.

Modern single mode fiber has very low attenuation (less than 0.01dB/km). But more importantly you don't have to use opto-electrical repeaters to boost the signal. What you do is using purely passive dispersion control by mixing different kinds of fiber and compensate for the rest dispersion using chirped fiber bragg gratings. To boost the signal you splice in rare earth doped fibers (Erbirum, Yttrium) which acts as optically pumped optical amplifier.

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Re:OCaml All the Way Down – How Jane Street Builds FPGA Desi... by zoggenhoff on Sunday September 30, 2018 @09:45PM (#18109453)

When you write "modern" how long ago would that have been installed?

/me trying to get a handle on optical development.

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Re:OCaml All the Way Down – How Jane Street Builds FPGA Desi... by datenwolf on Monday October 01, 2018 @10:14AM (#18112680)

The basic principle has been invented over 30 years ago in 1987: https://ieeexplore.ieee.org/document/4258955

They're used in long haul communication for some 15 years or so. They're especially useful in submarine cables, for the sole reason, that new optical transmission schemes(modulation, wavelength multiplexing and so on) can be implemented by just replacing the equipment on either end, without the need to replace components down there on the seabed.

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Re:OCaml All the Way Down – How Jane Street Builds FPGA Desi... by joejoint on Sunday September 30, 2018 @03:35PM (#18107930)

Speed of light is a universal physical constant. What you referring is that the space the light has to travel in the optic cable is way bigger then what it would be with straight line of sight between MW towers.

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Re:OCaml All the Way Down – How Jane Street Builds FPGA Desi... by detaro on Sunday September 30, 2018 @03:54PM (#18108029)

The constant referred to as "speed of light" is speed of light in vacuum. Light slows down different amounts in different media.

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Re:OCaml All the Way Down – How Jane Street Builds FPGA Desi... by mhh__ on Sunday September 30, 2018 @04:12PM (#18108133)

Semantics, at best...

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