Eatontown, N.J.-based Opnext Inc., a designer and manufacturer of optical modules and components, has reached an agreement to acquire privately held StrataLight Communications Inc. of Los Gatos, Calif., for approximately $172 million. Purchase of the latter, a developer and manufacturer of 40-Gb/s line-side optical subsystems, will include 26.55 million common shares and $30 million in cash.