I'm having some trouble finding a definite answer. I use a light loss tester to test our fiber (we dont have an otdr) and am unsure as to the acceptable light loss for 1310 SMF. So far I've figured out anything under 1db loss works. Anyone know a better reference?
The exact power budget depends on the PHY used.
Power budgets: 1000BASE-LX10 has a budget of 10 dB (6 dB insertion loss + 4 dB link channel loss - clause 58.5) while 10GBASE-LR has a budget of 9.4 dB (6.2 dB insertion loss + 3.2 dB link channel loss - clause 52.6.3).
This is by IEEE standard of course, mileage on specific transceivers may vary - the higher the budget the longer the reach.
Expected loss: For deployed fiber, OS1 has a maximal attenuation of 1 dB/km (ISO/IEC 11801) and OS2 .4 dB/km (ISO/IEC 24702). Substract .1 dB per (good) splice and .1 to .2 dB per connection.