# BER calculation formula

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BER calculation formula:
B1 BER = Number of B1 errored blocks/(N x 270 columns x 9 rows x 8 bits x 1s x 8000 frame/second).
Note: N in the preceding formula is the number in STM-N.
B2 BER = Number of B2 errored blocks/{[(261columns x 9 rows) + (9 columns x 5 rows)] x 8 bits x 1s x 8000 frame/second}.
B3 BER = Number of B3 errored blocks/(261 columns x 9 rows x 8 bits x 1s x 8000 frame/second).

###### Other related questions:
Threshold of the pre-FEC BER that will trigger post-FEC bit errors on LWF boards using the FEC/AFEC function in BWS 1600G devices
When the pre-FEC BER reaches 10E-7, the system will start bit error processing. (The actual error correction limit of Huawei WDM devices can reach around 10E-5 for G.975-compliant FEC, and reach around 10E-3 to 10E-4 for AFEC.)

Base of the OSNR = 10 × log (Ps/Pa) formula
The base of the OSNR = 10 x log (Ps/Pa) formula is 10. Strictly speaking, lg should be used instead of log. However, the default base is recognized in the industry and related standards. Therefore, "log" is still used in the formula.

Formula used to calculate the OSNR
OSNR = 10lg (S/N)

Method used to calculate a linked clone VM's storage resources
The storage resources required by a linked clone VM are calculated as follows: Formula: ROUNDUP (N/128, 0) x Size of the base volume + N x Average size of delta volumes. The average size of delta volumes needs to be calculated based on the site situation. Generally, the estimated average size is 5 GB.

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