EXFO FTB-7000 OTDR for FTB-200 v2 - Manual (Page 107)

OTDR 93
9 Customizing Your OTDR
You can customize the appearance and behavior of your OTDR application.
Selecting the Default File Format
You can define the default file format the application will use when you
save your traces.
By default, traces are saved in native (.trc) format, but you can configure
your unit to save them in Bellcore (.sor) format.
If you select the Bellcore (.sor) format, the unit will create one file per
wavelength (for example, TRACE001_1310.sor and TRACE001_1550.sor, if
you included both 1310 nm and 1550 nm in your test). The native format
contains all wavelengths in a single file.
You can only modify the file format from the Save File dialog box, which
means you need to save at least one trace in the desired format before it
becomes the new default file format.
Note: The application will only display this dialog box if you have activated the
feature to always be prompted when you save a file (see Enabling or
Disabling File Name Confirmation on page 94).