ONI Systems Corp. April 1 announced that metro optical systems rival Nortel Networks Corp. has agreed to dismiss all claims related to four patents purportedly infringed upon by ONI, but is pursuing litigation on a fifth. Nortel’s original suit was filed on March 10, 2000, just prior to ONI’s filing for its initial public offering. The four patents dismissed in the suit pertain to SONET technology that Nortel alleged ONI had infringed upon in its dense wavelength division multiplexing (DWDM) systems, an ONI spokesman says. The fifth patent pertains to a technique for passive passthrough of optical signals in a DWDM system, the spokesman says. Since the suit was filed, ONI says it has vigorously countered all of Nortel’s claims and will continue to do so with the remaining Nortel patent at issue.