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SM is single mode
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MM is multi mode
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SM has 9 micrometer core diameter
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MM has 50-62 micrometer core diameter
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SM used in long distances transmission
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MM used for short distances transmission
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SM used in WDM technology ( specially DWDM )
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SM should use Single mode SFP
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SFP is small form factor pluggable and it’s the optical module that convert optical to electrical and vice versa
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We can use 1310 and 1550 nm in single mode
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We can use 850 nm in multimode
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SM has higher immunity to modal dispersion
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ITU standardize G 652 , G 653 and G 655 to work in single mode optical
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G 652 and G 655 is the most common single mode optical fiber used in DWDM technology
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G 653 can be used in SDH
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We can’t use G 653 in DWDM because it’s zero dispersion point is in 1550 nm and it can lead to four wave mixing
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