Optical link budget refers to the effective distance of optical signal transmission. There are three main factors;
1、Transmitting optical power of the transmitting end;
2、Receiving sensitivity of the receiving end;
3、Optical fiber attenuation coefficient;
Calculation formula: link budget L=（Ps-Pr-Me-Ac）/（Af+As+Mc）（km）
Ps：Transmitting light power, unit dBm, Ps=（Pmax+Pmin）/2，Pmax，Pmin is the maximum and minimum of the average transmitting optical power
Pr：receiving sensitivity, unit dBm,
Me：equipment redundancy, generally 3~4dB,
Ac：attenuation of other connectors between transmitting and receiving, such as patch cords, adapters, etc. patch cords are generally 0.1dB per port and 0.2dB per adapter.
Af：optical fiber attenuation coefficient, 1310nm @0.36dB/km，1550nm@0.22dB/km,
As：average welding attenuation of fixed joints, 0.04~0.05dB,
Mc：optical fiber cable redundancy: 0.05~0.1dB
Take our product OP3980D as an example: 10G SFP+ ZR 1550nm 80km
Theoretical value
Ps：Average Optical Power, Pmax=5dBm,Pmin=0dBm, Ps=2.5dBm
Pr: Receiver Sensitivity,Pr=-23dBm
Me: 0
Ac: 0.2dB(Take a patch cord as an example)
Af: 0.22dB/km
As: 0
Mc: 0
L=（Ps-Pr-Ac）/ Af=(2.5-(-23)-0.2)/0.22=114.5km
Reference value of a customer's actual link (equipment redundancy 3dB, optical fiber cable redundancy 0.05dB)
Ps：Average Optical Power, Pmax=5dBm,Pmin=0dBm, Ps=2.5dBm
Pr: Receiver Sensitivity,Pr=-23dBm
Me: 3dB
Ac: 0.4dB(One patch cord, one adapter)Af: 0.22dB/km
As: 0.05dB
Mc: 0.05dB
L=（Ps-Pr-Me-Ac）/（Af+As+Mc）=(2.5-(-23)-3-0.4)/(0.22+0.05+0.05)=69.1km
*Different actual link parameter values are different and need to be calculated based on actual conditions.
