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Photovoltaic power converters transform optical power into electrical power, which is inherently immune to RF, EMI, high voltage, and lightning effects. Capable of powering electronic circuitry directly over optical fiber in a wide variety of applications, this technology has been validated in industries such as electric power, communications, remote sensing and aerospace. From no more than a laboratory curiosity less than fifteen years ago, power-over-fiber, or photonic power, has established itself in thousands of industrial operations worldwide. Optical energy for pre-amplifiers or lowpower transmitters as well as switches and relays can be efficiently delivered through noise immune and non-conductive optical fiber. These advantages are also readily available for safe and arm applications since optical fiber is immune to electrical noise, magnetic fields and conduction of unexpected electrical currents. Since it is made from glass, a dielectric fiber is impervious to electromagnetic interference. High optical power is readily delivered through fiber, and conversion of optical to electrical energy at the remote site with efficient photovoltaic converters is routine.

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The feasibility of inducing a compressive residual stress in the matrix of a Nicalon-fiber-reinforced BMAS-glassceramic-matrix composite through a creep-load transfer treatment was studied. Specimens were crept at 1100°C under constant tensile load to cause load transfer from the matrix to the fibers, then cooled under load. Upon removal of the load at room temperature, the matrix was put into compression by the elastic recovery of the fibers. This compressive residual stress in the matrix increased the roomtemperature proportional limit stress of the composite. The increase in the proportional limit stress was found to be dependent upon the applied creep stress, with an increase in creep stress resulting in an increase in the proportional limit stress. Acoustic emission results showed that the onset of significant matrix cracking correlated closely to the proportional limit stress. Changes in the state of residual stress in the matrix were supported by X-ray diffraction results. Fracture surfaces of all specimens exhibited fiber pullout behavior, indicating that the creep-load transfer process did not embrittle the fiber/matrix interface.

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