Power Meter Design Minimizes Fiber Power Measurement Inaccuracies

Manufacturers of multiplexers, attenuators, amplifiers, and other fiber-optic components must characterize their products for parameters such as insertion loss and polarization-dependent loss. Insertion loss is usually accomplished by measuring output power variations before and after the component has been connected to a laser source. Polarization-dependent loss is measured by varying the input polarization to the device, and measuring the variation in power as the polarization vector is swept through all possible angles. The power meter used to perform these measurements may be sensitive to these types of variations, compromising measurement accuracy of the component under test. Most power meters, for instance, are sensitive to changes in polarization as well as uniformity of illumination of the detector surface and position of the fiber end with respect to the detector. In practice, integrating spheres are used to reduce these sensitivities.