Abstract: An apparatus and method for abrasively processing an article involves the use of an abrasive product provided with a machine discernable pattern representative of information of varying types. The pattern is read while the abrasive product moves relative to the article, and is used to control the movement of the abrasive product relative to the article. The pattern may include one or more of a machine discernable electrical characteristic, optical characteristic, topographic characteristic or magnetic characteristic. Reading the pattern may involve one or more of electrically, optically, mechanically or magnetically reading the machine discernable pattern provided on the abrasive product. The pattern may include one or more of indicia, protrusions, depressions, holes, voids, color or pigment variations, bar codes, magnetic transitions or periodic markings. The pattern may include one or more of indexing information, servo information, alignment information or abrasive product identification information.

Abstract: In known Faraday effect current sensors, light is fed into a polarizer, through a coil of field-sensitive optical fiber, and into a polarization measuring device. Such a current sensor can provide greater accuracy of current measurement by using a polarizing optical fiber as its polarizer and splicing the polarizing fiber to the input end of the optical fiber coil. The exit end of the optical fiber coil can be spliced to a second polarizing optical fiber, the other end of which is optically connected to a photodetector. In another embodiment, a mirror at the exit end of the optical fiber coil reflects light back through the coil to second and third polarizing fibers which in turn are optically connected to a pair of photodetectors, thus doubling the Faraday rotation while canceling out reciprocal optical effects.