Hi fellow,
On Router 2811, if you have modular slots available, put HWIC-1GE-SFP Card, in addition put GLC-LH-SM module in it.
In 3750, you'll be having by default 2 SFP ports, for that you need to just put GLC-LH-SM module in SFP.
and in both the modules you can put your monomode LC type fiber connector.
Rate if it helps
Regards,
Abdul Rafay