I think you will find the "monitor" port is most likely to be used for "lawful" intercept by unnamed government entities. -----Original Message----- From: NANOG [mailto:nanog-bounces@nanog.org] On Behalf Of Colton Conor Sent: Tuesday, 20 June 2017 8:14 AM To: Faisal Imtiaz <faisal@snappytelecom.net> Cc: nanog list <nanog@nanog.org> Subject: Re: DWDM Mux/Demux using 40G Optics Thanks for the answers. From the sounds of it, no one knows the real difference between the expansion port, 1310 port, and 1550 port. For real world applications, I would assume the monitor port would be to plug in a handheld meter, and see which channels are coming through that node without breaking the ring. Not sure if their would be a monitor port for both directions is you were using a OADM? On Mon, Jun 19, 2017 at 2:38 PM, Faisal Imtiaz <faisal@snappytelecom.net> wrote: