Attenuation is impacted in both directions on both spans and looks to be about the same in each direction. A third party characterization shows loss at what we expected. The TX levels from each end stay stable. The amplifier node is co-located in an ISPs equipment room and environmentals are controlled well.

Any other ideas? Do you think we should present this to the fiber vendor?

Thanks for your help.

Interesting... two spans with both TX and RX fibers impacted.

Are the impacted spans on opposite sides (East and West) of the amplifier node?

Maybe an OTDR shot at high and low outside temps would isolate a high attenuation point in the network; splice point, pedestal, CO, other, that might point to an issue.

Gut tells me it is not a fiber mfg issue, but they may be able to lend some ideas due to experience.

Thanks for your reply.

The impacted spans are on opposite sides of the amplifier node. Just to be more clear, my reference to the fiber vendor is the company we lease the fiber from, not the manufacturer. It might be difficult to schedule a OTD and try to predict high and low temps etc. Can anyone think of why an amplifier node would cause the these fluctuations if it isn't fiber. The output power on the nodes at the end points of these spans shows very stable output +-0.1 dB.

Are you amplifying a single-channel on these spans?

What optical amplifier is being used?

What are the terminating cards on the end of the spans.

Are there any alarms?

Sorry, but I may be just not understanding the installed network and am overlooking something.

Hi,

Thanks for your interest.

There are 4 channels on the affected spans. There haven't been any alarms since we added attenuation to the MXPP trunk RX ports to cover the power fluctuation and we increased the range of expected span loss. The terminating cards are MXPP configured with client ports as 1Gig Ethernet. One end of all 4 channels terminate at “E” site at one end of the amplified spans with the other end of the channels at 4 different sites, one of which is the other end of the affected spans. The amplifier node “NL-1” is actually an OADM without any client cards installed or circuits provisioned with a local drop. Slot1=OPT-BST, slot2=OPT-PRE, slot3=AD4C, slot15=AD4C, slot16=OPT-PRE, slot17=OPT-BSTE. The AD4C express ports connects sides A and B on NL-1. NL-1 side A connects to node “E-1” side B over 59km of fiber with MXPP cards in second chassis. NL-1 side B connects to node “S-2” side A over 117km. All other sites including E and S have a ROADM type setup with either OPT-BST or OPT-BSTE boost amps, OPT-PRE, 32WSS and 32DMX cards. At the E site, there is a second chassis, E-2 with 4 MXPP cards and side A of E-1 has BST, PRE, WSS, and DMX cards. The S site shelf 2 has a second chassis S-1 with BST, PRE, WSS, and DMX cards on both side A and B. S site shelf S-2 has 4 MXPP cards on side B and BSTE, PRE, WSS, and DMX cards on side A. Since the addition of these new spans was to finish our build-out and provide a redundant path, I think the E site is the only one without any pass-thru circuits.

I'll try attaching a basic network drawing as a png file. Distances are in miles.

Have you check the gain of your amplifier,when you are experiencing this fluctuation?. Can be a problem with your amplifier gain?

Like Tom i dont suspect the fiber as problem with fiber can be digital like effect either something or nothing.

Thanks.

Sorry, I grouped my reply to you in with another. The gain and output at the end nodes of the problem circuit stays very stable.