Making a neutrino beam is remarkably convoluted. https://en.wikipedia.org/wiki/Accelerator_neutrino
>The process of the muon neutrino or muon antineutrino beam production consists of the following steps[1][2]:
>Acceleration of a primary proton beam in a particle accelerator.
>Proton beam collision with a fixed target. In such a collision secondary particles, mainly pions and kaons, are produced.
>Focusing, by a set of magnetic horns, the secondary particles with a selected charge: positive to produce the muon neutrino beam, negative to produce the muon anti-neutrino beam.
>Decay of the secondary particles in flight in a long (of the order of hundreds meters) decay tunnel. Charged pions decay[3] in more than 99.98% into a muon and the corresponding neutrino according to the principle of preserving electric charge and lepton number...
There's several different places in this chain where you could modulate the beam by turning various magnets on or off. Probably not in the proton accelerator.
Unfortunately, "long string of expensive experimental equipment" means "not efficient". From the paper:
>A neutrino source delivering muons at a rate of 10^14 s^−1 with an energy of 150 GeV would require about 4 MW in proton beam power and 2.4 MW acceleration power, which for a 10% electrical efficiency translates into a total power consumption of roughly 65 MW.
Yow. Something like ten times more power than the NuMI neutrino beam. He concludes this transmitter could do something like 100 bits/s to a stationary detector string anchored at the ocean bed. Deeper the better, for shielding against cosmic rays and solar radiation. Would be tough to put a neutrino detector close enough to a financial hub and still get useful bandwidth.