OSNR meaning and calculation

Optical signal-to-noise ratio (OSNR) is used to quantify the degree of optical noise interference on optical signals. It is the ratio of service signal power to noise power within a valid bandwidth.

When the signal is amplified by the optical amplifier (OA), like EDFA, its optical signal-to-noise ratio (OSNR) is reduced, and this is the primary reason to have a limited number of OAs in a network.

The OSNR values that matter the most are at the receiver, because a low OSNR value means that the receiver will probably not detect or recover the signal. The OSNR limit is one of the key parameters that determines how far a wavelength can travel before regeneration.

OSNR serves as a benchmark indicator for the assessment of the performance of optical transmission systems. DWDM networks need to operate above their OSNR limit to ensure error–free operation. There exists a direct relationship between OSNR and bit error rate (BER), where BER is the ultimate value to measure the quality of a transmission.

OSNR calculation