Operation of a laser interferometer with a noncooperative target surface, and on a substantial span of displacement (1 m), is reported for the first time to our knowledge. In the paper, we first analyze the errors of an interferometer operating in the speckle pattern regime, then propose the technique of tracking the speckle relative maximum amplitude as a solution for problems so far preventing interferometric measurements of large displacements. Examples of the speckle-statistics improvements are reported. Residual errors are of the order of few wavelengths on a 1-m displacement, indicating that a 10 6 -class instrument can be developed. The proposed approach has been implemented with an injection interferometer.

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In this paper, a technique for spatially resolved chromatic dispersion measurement of installed optical fiber links is presented. The method is based on the analysis of bidirectional optical time-division reflectometer (OTDR) traces at different wavelengths obtained by a specifically designed tunable external source. Measurement accuracy is improved through a particular algorithm that corrects the OTDR nonlinearity error. Experimental data on spatially resolved chromatic dispersion of installed dispersion-shifted and nonzero-dispersion fibers are reported.Index Terms-Chromatic dispersion measurements, mode field diameter measurements, tunable optical time-division reflectometer.

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Noise in 1550 nm gain-clamped and conventional SOAs is studied using a detailed device model By dividing the amplifier in M longitudinal sections we are able to account for longitudinal non-uniformity of the carrier density We use a rate equation for locally averaged values of carriers and photons density for each section, obtaining a highly non-uniform spatial profile of carrier density for a conventional SOA, due to local saturation caused by ASE or signal photons At least M = 8 sections are required to accurately model the noise figure. The model is then applied to a DBR-type gain-clamped SOA, whose noise figure is studied as a function of input power and lasing wavelength. We show that changes in the spatial carrier profile caused by the input signal significantly affect the noise figure, even when the gain is constant. A new method for Gain-Clamped SOA noise figure reduction is also proposed, based on unbalanced Bragg reflectors An improvement of noise figure as large as 2 dB is devised.