97-98 t0 preliminary results

Preliminary t0s from 7-May-98

These results include the corrections from the interstring analysis, and they are accurate to ~5 ns. Here is a detailed description from Christopher of the problems in the standard analysis.

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97-98 Fiber lengths 24-Feb-98

The 97/98 fiber lengths are derived from several sets of measurements made at UCI (Oct-95 and Oct-96) and the south pole (Jan-97, Dec-97, Jan-98, and Feb-98). All of these measurements have been cross-calibrated, and normalized to the complete set of measurements made in Dec-97. The results are reported in the multimode length table and single-mode length table.

I make three assumptions in my analysis.

  1. The calibration factor for the Dec-97 measurements is constant, because I made the measurements over a short period of time.
  2. The calibration factor for any one string is constant, because the measurements are also done over a short period of time by one person.
  3. That there are no DC offsets in the 850 nm OTDR measurements.
I compute the ratios of the measurements for each fiber with respect to the Dec-97 measurements. The string-by-string ratio plot and the MM and SM ratio histograms shows the calibration differences. Based on these results, I group the measurements as shown by the dotted lines in the string-by-string plot, calculate the statistics for each group, and rescale the measurements with the median to the Dec-97 scale. The master length results use the first of
  1. the rescaled Jan-98 measurements,
  2. the Dec-97 measurement,
  3. or the rescaled UCI measurements.

After rescaling there are still some discrepancies. These are listed in string/fiber order or sorted by magnitude. Please note that string 9, fiber 3, MM & SM are particularly unreliable, because they seem to have changed length during 1997.

The multi-mode residuals and single-mode residuals are the differences of the original sets from the final master set.

The Dec-97 single-mode residuals are plotted with and without the 'o' data points.

97-98 Fiber transit times 24-Feb-98

The fiber transit times are determined by calibrating the previous fiber length measurements with the 532 nm OTDR. They are available

A zero entry indicates no data for the fiber.

The individual ratios are histogrammed here, and the measurement statistics are here.

At this stage of the analysis I am convinced that the multi-mode results are more reliable than the single mode results, and that the multi-mode fibers should yield better t0s as long as there is enough data to characterize the LE distribution.