BER (Bit Error Rate)

BER is a basic digital-transmission quality metric, defined as the ratio of the number of incorrectly received bits to the total number of transmitted bits over a given period.

What affects BER?

BER depends on the signal-to-noise ratio (OSNR) at the receiver input, the chromatic and polarization dispersion (PMD) accumulated along the route, fiber nonlinear effects, and the quality of the transmit/receive components. Typical telecom-system requirements call for BER below 10⁻¹² after forward error correction (FEC).

Applications

BER is a key acceptance criterion for an optical transmission system design — engineers simulate the entire link (laser, fiber, amplifiers, receiver) to predict BER before deploying the physical network and choose an appropriate power margin.

Related terms

Optical Q-factor

Chromatic dispersion

Coherent detection