Abstract: An opto-mechanical switch suitable for use in optical telecommunications systems comprises an input port and two output ports interconnected by an optical path, an optical element and an actuation mechanism for moving the optical element relative to the optical path so as to change coupling of light beams between the input port and the output ports. The optical element is supported by a flexible suspension unit comprising a pair of mutually-spaced twin elongate flexures. Each of the pair of flexures is attached at one end to an anchorage and at its other end to a mounting for optical element. The flexures are identical in length and flexibility and are spaced apart in the direction of displacement of the optical element. In use, when the actuator displaces the optical element, the flexures flex in common in the direction of displacement of the optical element. The optical element may be an optical fiber, a mirror, a prism, and so on.

Abstract: A method and apparatus is provided for injecting an optical test pulse mid-stream into an optical path to be tested by providing a switch that in normal transmitting and receiving of data includes two lenses separated by a gap. Data is usually transmitted across the gap from one lens to the other. In a test mode where OTDR is to be performed, a prism functioning in a similar manner to a periscope is moved into the gap between the lenses to couple/inject a test pulse into one of the lenses. An arrangement is described wherein either side of transmission line on either side of the gap can be tested.

Abstract: The chromatic dispersion of an optical fiber such as a 10 to 50 km length of single mode fiber is measured by launching into the fiber the outputs of at least three commonly modulated semiconductor lasers having output wavelengths close to a region of minimum chromatic dispersion of the fiber. At a remote end of the fiber the relative phases of the signals from the three lasers are determined and a chromatic dispersion profile of the fiber is derived from the measured relative phases and the output wavelenghts of the lasers by assuming a parabolic relationship between signal propagation times and wavelength. The profile can be determined by defferentiating a parabolic function fitted to the three date points derived using said three lasers or by directly generating a linear relationship between chromatic dispersion and wavelength on the basis of two values of chromatic dispersion derived from these three data points.

Abstract: A variable attenuation electro-optic device has a lens for collimating light from an input fiber and for focussing light into an output fiber. The optical path of light passing through the device passes through a dynamic scattering liquid crystal cell whose optical transmissivity can be varied by varying an AC electric field applied across it. Reflective and transmissive embodiments are described using one or two lenses of the Selfoc.RTM. type. The applied AC introduces a frequency component into the attenuation which is suppressed to particularly adapt the device for use as an attenuator or enhanced and modulated to particularly adapt the device for use as a modulator.