# What is dB&dBm?

Created Jun 13, 2018 19:26:02Latest reply Nov 29, 2018 12:25:22 318 11 3 0
 ndB is a ratio of the amount represents two power (P1/P2),  is a relative value,  using the base-10 logarithm is multiplied by 10 to represent,  as 10lg (P1/P2);  ndBm represents power unit,  is an absolute value,  related to  mW,  the base 10 logarithm divided 1mW expressed as 10lg (P/1mW);  Mainly based on two considerations,  1) Represent very large or very small numbers,  simplifying the numbers,  for example:  1000 times gain,  receiver sensitivity 0.001mW,  which representation of gain=30dB, -30dBm receiver sensitivity are much simple . 2) It can turn the multiplication and division into addition and subtraction,   by checking the number tables to handle complex calculations,  great benefits to pre-computer era. From group: Transport&Access Network
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 useful info!
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Raluca29  Moderator   Created Jun 14, 2018 22:09:46 Helpful(0) Helpful(0)

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Anca  Mentor   Created Jun 14, 2018 22:56:47 Helpful(0) Helpful(0)

 Thanks for sharing!
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Innuendo  Mentor   Created Jun 14, 2018 23:01:57 Helpful(0) Helpful(0)

 thanks for sharing!
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Trans_HB  Moderator   Created Jun 15, 2018 00:33:39 Helpful(0) Helpful(0)

 can u explain to me more about formula :Ptotal=Ps+10LogN?
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Trans_HB  Moderator   Created Jun 15, 2018 00:34:09 Helpful(0) Helpful(0)

 can u explain to me more about formula :Ptotal=Ps+10LogN?
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V84083177  Moderator   Created Jun 15, 2018 20:42:11 Helpful(0) Helpful(0)

 Posted by Trans_HB at 2018-6-15 00:34 can u explain to me more about formula :Ptotal=Ps+10LogN? are you referring, how to calculate the output power on DWDM?Pcomposite = Pchannel + 10logN – Insertion loss (where N is the number of channels)For example if we have a DWDM 8 channel multiplexer. The input power is 0 dB (insertion loss = 5 dB).= 0 + 10log8 – 5 dB = 0 + 9 – 5 dB = 4 dB
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 Useful info!
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wissal     Created Jun 16, 2018 01:09:09 Helpful(0) Helpful(0)

 Thank you for the reminder of this basic information
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