Bit error ratio

In telecommunication, an error ratio is the ratio of the number of bits, elements, characters, or blocks incorrectly received to the total number of bits, elements, characters, or blocks sent during a specified time interval.

The most commonly encountered ratio is the bit error ratio (BER).

Note: For a given communication system, the bit error ratio will be affected by both the data transmission rate and the signal power margin.

Note 1: Examples of bit error ratio are (a) transmission BER, i.e., the number of erroneous bits received divided by the total number of bits transmitted; and (b) information BER, i.e., the number of erroneous decoded (corrected) bits divided by the total number of decoded (corrected) bits.

Note 2: The BER is usually expressed as a coefficient and a power of 10; for example, 2.5 erroneous bits out of 100,000 bits transmitted would be 2.5 out of 10⁵ or 2.5 × 10^-5.

Note 3: On good connections you have an BER below 10E-9. The test time for a 95% confidence Level on a:
STM-256 / OC-768 = 1 s
STM-64 / OC-192 = 3 s
STM-16c / OC-48c = 12 s
STM-4c / OC-12c = 48 s
STM-1 / OC-3 = 3.2 min

Source: from Federal Standard 1037C and from MIL-STD-188