Apple Faces Demand to Bar Watch From U.S. as Fight Widens (1)

Masimo Corp. is expanding its legal fight against Apple Inc., filing a patent-infringement complaint at the U.S. International Trade Commission that seeks to halt imports of the Apple Watch.

Apple’s Series 6 smartwatch infringes five patents for devices that use light transmitted through the body to measure oxygen levels in blood, Masimo said in a complaint filed at the Washington agency. The patented technology is key to Masimo’s core business and Apple is unfairly copying the features, the company said.

Masimo, which develops signal-processing technology for health-care monitors, and its spinoff, Cercacor Laboratories Inc., first sued Apple in ...