Effect on Bandwidth/Speed due to poor Fibre optic cable.

[rajesharihant]

Experts, GM to All. 

I have a situation which is a bit peculiar and looking for some advices. 

I have two sites - both are roughly 50 Kms apart. both are OT ICS systems sites. 

I am using somewhat Old Fibre cable which was laid say 10 years ago. 

I got the Loss calculations via OTDR - and there are losses - but within the loss budget. 

Now - I have 9200 - GBPS switches on both sites and they are connected via this FO cable. 

I have OT ICS systems at both sites & need to communicate with each other via this GBPS/FO link.  

Sometimes I assumes the link is very slow. If I copy a file from site-2 to site-1 - it clocks only about 1 MBPS or less of data transfer rate. 

Any advice on this? does the quality of Fibre responsible for lack of speed/bandwidth?

how can I ensure that the 1 GBPS capability of the 9200 is fully being utilized?

also, is there any easy methode to calculate the bandwidth of the link?

Much appreciate your support if possible. 

Raj.

[Leo Laohoo]

Are both strands having poor readings or just one strand?

If the fibre optic is >10 years old, I am going to presume it is OS1.  Is this correct?

[rajesharihant]

Thanks Mr. Leo, 

What do you meant by OS1? we are having single mode fibre. 

I have redundant cables for the link. so, total 4 FO cores are in use. 

we did the OTDR and light loss calculations for 48Kms of length. and for all 4 cores the losses are within the budgeted loss of 37 dB. 

Site-1 PP	Tx Power (dBm)	Site-2 PP	Rx Power (dBm)	Total Loss (dB)
P33	-2.81	P17	-28.9	26.09
P34	-2.81	P18	-34.3	31.49
P35	-2.81	P33	-33.1	30.29
P36	-2.81	P34	-38.2	35.39

[Leo Laohoo]

I'd be tempted to just use a circulator with the first strand (and dump the rest).

@Marvin Rhoads, @Tom Randstrom, any opinions?

[Tom Randstrom]

37dB loss is extremely high for a 48km link. I would have expected <20dB loss. What optical receiver module are you using within the 9200? 

Typically with a digital optical link, if the link is established, the bandwidth it supports is the rated speed of the device. If the throughput of the link is only 1mbps, it is probably a higher layer issue and not the link. Was this setup bench tested using these 9200s interconnected over a shorter jumper cable? 

Thanx!