Publisher Summary This chapter describes the advanced evaluation techniques in interferometry The chapter discusses the methods that rely on the adjustment of a fringe pattern The chapter examines the historically older interpolation methods where the phase information is extracted from the positions of the extrema The chapter also discusses more general methods that deliver the phase in a more continuous form A comparison of the different methods for phase evaluations necessitates a consideration of the error sources and limitations These error sources for the case of phase sampling interferometry (PSI) have been discussed The error causes are classified into statistical errors (measuring errors that can be diminished in their influence by averaging) and systematic errors (errors that cannot be quenched) The interferometers used in the assessment of test data are rather complex, thus, there is some necessity for calibration The interferometer aberrations, even with ideal test samples, are caused by deviations of optical elements and to also by the state of adjustment The chapter identifies the types of error sources—namely, environmental errors, errors that are dependent on the method, and errors typically encountered in interferometry

IV Advanced Evaluation Techniques in Interferometry

Periodic phase changes in the 10(-6) -rad region have been induced and detected in a single-mode all-fiber Mach- Zehnder interferometer by stretching the fiber with a piezoelectric cylinder driven at frequencies between 40 and 10(4) Hz.

Measurement of small phase shifts using a single-mode optical-fiber interferometer

The present work is a contribution to the field of linear displacement measurements by optical means. For that purpose, a brief overview of some existing solutions is presented and two systems for axial linear displacement measurement based on light intensity detection are introduced. The systems have redundancy and were designed with the purpose of achieving identification and automatic correction of errors arising from inadvertent angular variations between the sensor and the light beam positions.

An overview and a contribution to the optical measurement of linear displacement

Fiber-optic filters can be used for processing wideband radio-frequency, microwave, and millimetric signals directly in the optical domain avoiding costly electrooptic and optoelectronic conversions. Because these filters sum signals on an intensity basis, they are bound to be positive and, hence, heavily restricted in their achievable performance. Nevertheless, such filters are the only choice because positivity is a consequence of the underlying physical mechanism. In this paper, the authors present a new design methodology to realize an arbitrary filter as a difference of two positive filters, thus overcoming any performance limitation.

The design of fiber-optic filters

A mathematical model is presented that predicts birefringence changes in an optical fiber as the cladding is removed. This model approximates a highly elliptical fiber core with a rectangular dielectric waveguide. The birefringence calculations obtained with the model compare well with experimental evidence obtained with real-time birefringence monitoring during cladding removal by chemical etching. The information is used to control the amount of cladding removed from a D fiber to within ~ 0.05 μm for use in the production of passive optical fiber components.

Analysis of etching-induced birefringence changes in elliptic core fibers.

A variety of optical components have been made directly from single-mode fibers. These components can be combined to construct in-line all-fiber systems such as fiber gyroscopes, fiber Raman lasers, local area networks, or coherent lightwave systems. This paper reviews the present state of passive and active single-mode fiber components. Passive components are polarizers, directional couplers, filters, and Faraday rotators. Active components require external control or optical power and include modulators, polarization controllers, frequency shifters, and amplifiers. Polarization is usually important in fiber components and discussions of polarization-maintaining and ordinary single-mode fibers are included.

R.P. De Paula

Papers

Single-mode fiber components