Bob writes:
Does anyone know if the new in-line optical amplifiers (not switches!) have any effect on quantum crypto messages?
Optical
repeaters have to pass your signal through an intermediate electronic stage anyway, since we have no purely optical valve/transistor equivalents (bosons don't interact with each other at all).
This is not true. There is now a whole technology of optical amplifiers for fiber communications systems that used Ettrium doped fibers pumped with strong light from a laser at a slightly shorter wavelength. These fiber optical amplifiers have gains in the order of 10-12 db in a section of special doped fiber only about 10 feet long. The current generation of undersea cables from the US to Europe use these amplifiers instead of the more traditional regenerating repeaters that convert the light to electronic signals, reclock the data stream and convert it back to light with another laser diode. There is no conversion from light to digital electronic signals all the way from Rhode Island to England - the same light pulses that go into the fiber on one side of the Atlantic come out on the other end without ever having been converted to electronic form in between. These amplfiers have enourmous bandwidth, and can be used to amplify several slightly different wavelengths of light allowing wavelength division multiplexing of multiple streams of light flashes of slightly different "colors" (all the current technology works at around 1500 nm which is well into the infrared). This can expand the capacity of a single fiber to four to six times the 5 Gb/sec that is the current state of the art. Dave Emery die@die.com
Can someone think of a reason why this wouldn't necessarily be so?
Cheers, Bob Hettinga
- alex