Remote fiber test systems are based on technique of optical time domain reflectometry (OTDR) and, in particular, on comparison check and current traces. Precision of tests is depended on choice of estimates and criterions of trace deviations. Estimates of deviations must be most sensitive to fiber optic parameter deviations. On other hand, its must be lowest sensitive to OTDR parameter deviations. The ways of mention problem decision are discussed. We offer one of solutions. This solution is based on analytical-statistical model. Some samples of numerical and experimental results are represented. Fiber optic communication lines, comparative method, OTDR, check traces, current traces, estimate, criterion of deviation, analytical-statistical model.