The Sor is a file format which is often create by OTDR. The file saves OTDR traces information like fiber length, attenuation, return loss and OTDR itself information, and some other filed (record) that added by OTDR users.
Generally, sor files can not opened directly by normal softwares/applications. Every OTDR manufacturer provide their own particular software for their OTDR.
Occasionally, some sor softwares are compatible with other sor files, but not completely. some fields may be lost. So, it is better to ask manufacturer about sor softwares. You can download it from their website or ask them send you by email. You can also check CD or USB that comes together with OTDRs.