Communication by lightwaves over ultra-thin light-weight glass fibers using bursts of light is becoming more and more a common occurrence. Efficient optical systems are being put to use in telephone and other communication systems, including undersea cable systems.
An optical communication system requires several basic devices. Most basic are a light source and channeling devices, such as, optical fibers and waveguides. In addition, devices are needed for encoding, decoding and switching between electric waves and lightwaves. Light sources are available in the form of lasers and light-emitting diodes (LED). Encoders and decoders are effected by electrooptic and magnetooptic materials; such as, lithium niobate, gallium arsenide and iron garnets. Switching is achieved by placing sections of ultrathin waveguides in close proximity to each other. Transfer of lightwaves to and from such waveguides is accomplished through prisms and diffraction gratings. Transfer of lightwaves between neighboring waveguide sections is accomplished by evanescent waves, i.e., waves extending beyond the boundaries of the waveguide proper.
It is an object of this invention to provide an optical data link connecting an analog electrical transducer to a remote monitor through an optical fiber without having to supply electric power to the modulator at the transducer site.
It is another object of this invention to provide direct modulation of the lightwave passing through an optical fiber by means of an integrated optics device.
It is still another object of this invention to reduce significantly the length of the optical fibers in a transmission link between a monitoring location and a remote signaling source.