Laser weld process improvements for optical isolator assembly

Optical isolators are used in lightwave systems to reduce feedback that could be propagated in the signal fiber. Several methods can be used to assemble and join the various components which comprise the completed device. Since the single mode fiber core is 8 microns in diameter, it is desirable to utilize a robust assembly technique which will produce a minimum of distortion during the assembly process. Process induced distortion could randomly change the device coupling which may have an adverse effect on operation yield. With the development of laser welding systems, devices can be manufactured with localized welds providing small amounts of thermal distortion. This paper compares two isolator assembly techniques: resistance welding and laser welding. A comparison of device power losses after the weld sequence and thermal cycling data shows that laser welding is a more robust and stable technique for isolator manufacture.