SONET and SDH, or Synchronous Optical Networks and Synchronous Digital Hierarchies, are multiplexing protocols which deliver information at high speeds over optical fiber using lasers or light-emitting diodes. A SONET tester or SDH tester ensures the proper deployment, operation and maintenance. SONET/SDH testers are used for analyzing the transportation of ATM frames (Asynchronous Transfer Mode), Ethernet connections and a variety of other sophisticated tasks. There are a variety of manufacturers of SONET/SDH tester like Anritsu, Keysight Technologies, Tektronix, VIAVI, and others. Contact an ATEC representative for help finding the best fit for you.