Abstract: The self-monitoring link utilizes a GRIN lens/blazed grating combination to multiplex an optical time domain reflectometry (OTDR) signal with data signals on a fiber optic communication link. An initial average OTDR reference signature for the OTDR signal on the link is determined and is compared with a continuously determined average OTDR signature. The reference signature and the continuously determined signature are compared and a warning or alarm signal is generated when the continuously determined signature differs from the reference signature by a preselectable limit. A microprocessor is provided to adjust the preselectable limit in response to the communication link operational parameters.

Abstract: The wavelength division multiplexer/demultiplexer includes a gradient index of refraction (GRIN) lens and a diffraction grating located adjacent to one end of the GRIN lens. The diffraction grating is adapted for switching from a first angle to a second angle with respect to the GRIN lens. For both path and terminal equipment redundancy, first and second input optical fibers are located at first and second input locations on an end surface of the GRIN lens. A first and a second plurality of output optical fibers are also located on this end surface of the GRIN lens. The input and output optical fibers are located so that optical energy will travel from the first input optical fiber to the first plurality of output optical fibers when the diffraction grating is oriented at the first angle and optical energy will travel from the second input optical fiber to the second plurality of output optical fibers when the diffraction grating is oriented at the second angle.

Abstract: A graded index of refraction (GRIN) lens/diffraction grating combination is used to monitor the output source peak wavelength of an optical source. As the output wavelength of a source varies, different detectors are activated. The output of these detectors is used to control a thermoelectric cooler which will raise or lower the temperature of the source so as to drive the output wavelength toward the desired peak output wavelength.